Energy Ltd. News #39
Copyright 2010 Craig Carmichael - May 2nd 2011
Month In Brief
* Hybridizing cars: Two Electric
Hubcap motors, with
gear sets? (having nylon planet gears?)
* Turquoise Battery Project: First Successful rechargeable salt electrolyte
battery. Mn-Ni, 1.5 V.
* Successful end to the NiMH dry cell car batteries as a research
(But I'll be getting lots of them for EV use!)
* Much paperwork/writing
* Independent franchises business model?
Electric Hubcap System
* Motor Configuration
* Shortest Motor
* Smaller Diameter, Too - new body parts molds
* Hall Sensor Circuit Board
* A3938 V2 Motor Controller Circuit Board
* Smaller 'production version' controller chassies: fewer
components and smaller controller plate allows smaller wiring box.
Electric Weel Motor Project (Electric Wheel
Motor... Rim Motor...)
* More metal parts have been cut, a better design emerges based on
improved Hubcap motor design. But other projects take precedence.
Planetary Gears Project
* No mechanical torque converter yet!
* Instead: hybridize
cars with Hubcap motors and planetary gears.
* Photos of gears and car installation.
* Lubrication: Oil Drip...
* ...or Nylon Planet Gears! Nylon gears make non-oil-filled
* Can't find nylon gears... maybe just great gobs of grease and
the metal gears?
Torque Converter Project
* New design idea: a variable ratio "planetary gear"?
Turquoise Battery Project
* Osmium - conductivity
* "Low" oxygen overvoltage may be the key cause of high self
* Refrigerator test, freezer test: self discharge is much lower at
* In salt battery, nickel
hydroxide forms naturally from nickel metal -- no need to make it.
* Rare earth hydroxides (La(OH)3) are used to increase oxygen
overvoltage. (Hence: my original
monel-lanthanum hydroxide mix is probably great stuff! But other rare
earths are probably better. -- Samarium or Neodymium?)
* Designs for next cell (complete design less sealed case).
* Cell made: self
discharge still high.
* Reversed the polarity: IT
WORKS! 1.5 V rechargeable cell holds charge.
Construction Manuals and information:
Electric Hubcap Motor
- Turquoise Motor Controller
- 36 Volt Electric
reflective rear electrodes to enhance DSSC Solar
- Simple Spot Welder
Hubcap Motor Kits, Parts - Build your own ultra-efficient 5 KW
- Sodium Sulfate
longevity additive & "worn
out" battery renewal.
- NiMH Dry Cell Car
Batteries (please e-mail me to order batteries)
- NiMH Custom Batteries (EVs, E-Bikes, Scooters, etc. - no extra
- NiMH individual Dry Cells (D - 10 AH, $10 -- AA - 2.5 AH, $2.50)
- Motor Building
...all at: http://www.TurquoiseEnergy.com/
April in Brief
The essential components to electrify a car seem to be coming
Hubcap motor with planetary gear, Motor controller
Forward-Off-Reverse switch and gas pedal potentiometer,
and a few kilowatt-hours of batteries. (The NiMH dry cells shown are
about 1 KWH total.)
(Final version of motor will be an inch thinner and 1/2 inch smaller
diameter; machine-drilled holes.)
Hybridizing Cars with Electric Hubcap Motor(s) + Planetary Gear(s)
After 7 continuous months of motor improvements, I think
now one could look far and wide and not find as
good a motor as the Electric Hubcap. Despite the time taken by motor
developments, there are working motor
controllers and better ones to come, and a choice of cheap lead-acid or
NiMH batteries (or lithium). But I
haven't been successful yet at creating the mechanical torque converter
to couple the motor to the wheel.
In order that hybridizing cars not be further delayed by
one laggard item, I've decided to try gearing
the motors to the wheels with planetary gears. The speed reduction will
be a compromise. Mid speeds will be great, but there'll be less torque
to start the car moving and high motor revs at higher speeds. It
appears it will probably be
possible to gear a small car for adequate low speed starting torque
allowing driving up to about 80 Km/Hr with two motors/gears, on left
and right wheels. Using a single motor would
definitely mean low top speeds - city driving only.
I ended up with a 2.8 to 1 Chrysler planetary gear which I
installed in last month's motor. I mounted it on the car and tried it
on the last day of the month. Disappointingly, it didn't move the car -
the usual sort of "almost but not quite" on my lumpy driveway and
"might just have moved on level pavement" - but I discovered the motor
controller was only giving it 55 amps instead of 127, so it had less
than half torque. I fear raising the limit in the controller will
simply blow the controller (and it's the only one working at the
moment), so the need to get the A3938 controllers working properly is
pressing. If I could find more planetary gears with different ratios,
I'd love to try them out. At 10 to 1 the car would doubtless have moved
and had great acceleration... up to the motor's top speed at 20-25
Km/hr. At 5 to 1 it probably would have worked (except maybe on steep
hills), up to about 40-50 Km/hr.
With two motors at the 2.8 to 1 gear ratio and full amps,
the car would have five times the torque of just one direct connected
motor. Is that enough for the streets? Fair chance... I guess I'll find
out when everything's ready!
NiMH Project Ends, a Success!
The NiMH Dry Cell Battery Project is
completed as an experimental research project. The cells work so well
as car batteries and to run heavy loads that there seems to be nothing
more to do but make batteries and use them or sell them. I can't say
how long they'll last, but it should be a very long time - maybe 15 to
25 years as a car battery. I accidentally left my running lights on for
a couple of
hours recently and the car started like nothing had happened. I will of
course be buying more to use for the electric motor projects. The first
three 'spare' 12 volters are already saving my bad
back from the stress of carrying 40-50 pound lead-acid batteries out to
my car for on-car motor tests.
Using them for car
batteries not only saves gas and makes your car a bit greener, it's
also the way to increase NiMH dry cell sales volumes, which is likely
to further reduce their already decreasing prices. I was e-mailed a
'coupon' this month from all-battery.com as a repeat customer for 15%
'D' cells, which brings them down to the lowest price yet: about 5 $US
list each - 417 $/KWH. So I put 80 more on my credit card - if I
can't sell NiMH car batteries I'll certainly use them myself as
EV batteries. (Indeed I plan to solder some more batteries together in
the near future, including a couple of 6 volt ones to get 42 volts.) 80
D cells is almost a KWH, about 1/6th of my minimum
target of 6 KWH for 50+ Km of local electric travel range. With D
cells, the weight of 6 KWH would be close to 200 pounds; with AA 140
with lead-acid about 600 pounds.
Turquoise Battery Project: a
successful battery at last!
Better than nickel-metal hydride batteries would be
batteries with a shorter name that are also more economical and hold
more energy by weight.
Two things of late have been between me and successful
electrolyte battery development. The first is trying to get enough
conductivity out of my graphite and cell structures and formulations
for high currents. Ten times better would be a big improvement and
closer to typical levels. Still, that by itself shouldn't prevent
making batteries that at least work, even if the current capacity is
The second and more perplexing problem was high self
discharge - minutes and hours instead of days and weeks. I've done
various things to raise hydrogen and oxygen overvoltage levels to match
my higher energy reactants, but this month's cell, made on the 25th,
discharged itself as rapidly as the previous ones.
Well, the ingredients in both electrodes could potentially
work in either direction. I reversed the charges on the morning of the
30th. By evening, it was holding -1.1 volts, and by the next morning,
lo and behold, it was working, the "backwards" charge holding for hours
at around 1.5 volts! I expect I have crated a Mn-Ni cell instead of
Ni-Mn, with the Mn charging to KMnO4 at +1 volt and the Ni to metal at
This appears to be a working, economical, rechargeable
cell with good energy density that should be very long lived. Going by
ingredients, it might cost twice as much as a standard single use dry
cell... and those are currently going for mere pennies in all the
But I have a few more things to try to get workable 2 volt
cells (33% more energy, all else being equal) before settling for 1.5
I'm still thinking about better ways of making the cells,
though. One can't spend a whole day or two to make a cell for anything
but the most limited and valuable uses. Homemade is great, but electric
transport really demands they be rolling off assembly lines into boxes
and shipped off in truckfulls. A good export commodity for BC and
With improvements and new developments coming fast and furious for some
months, I not only have trouble doing a fraction of what needs
developing, but the documentation has fallen far behind, and without
that, others can't readily make use of my work. With all the
changes, and now a motor kit available to order, the whole motor
was hopelessly out of date and needed rewriting, and the improved
format web site was still waiting for me to do several things. Even the
web intro/abstract to the Electric
Hubcap was two years old and contained major outdated or superseded
concepts and had to be rewritten. Then I got a phone call telling me
I'd done some things wrong on my income tax/SR & ED claim last
month, so I had that to deal with as well. By then it was getting close
to time for this newsletter.
So from the middle
of the month, I spent a lot of time typing at the computer, while I
also waited for Waterforce to get around to cutting my steel parts for
the geared hubcap motor (he did), and
for planetary gear suppliers and makers to get around to answering my
queries (they didn't).
A new motor controller manual is also needed, but it'll
have to await a working new motor controller, which is probably close
now. But the design had more problems than I suspected. This too shows
the problems with poor documentation: I've had design problems leading
to serious delays trying to make a motor controller from the A3938 chip
partly because the chip itself is poorly documented: sketchy datasheets
and no proper application notes.
A Business Model?
As I try to figure out how best to spread the Electric
Hubcap technology as it becomes available, one idea that comes to mind
is to do independent franchises. Here at the center, materials and
parts would be purchased and made in bulk, and wholesaled to the
franchised dealers and installers. Jigs and molds could also be
supplied for local
making of many or most of the components. The dealers then would
assemble the equipment, sell
and install it per installer and customer needs. An insurance pool that
would pay into could perhaps cover liability so that no one would risk
all to participate.
Electric Hubcap Motor System
The motor profile with flat plate rotor.
Finally, 1/2 inch is to be trimmed from the diameter - less 'lip'
outside the coils and rotor.
Pressing a drying PP-epoxy ring harder to try to squeeze out dry spots.
Afterwards I started backing the flexing PE plastic mold pieces with
and then bought 1" thick to replace these 1/2" pieces.
Just after putting out the March newsletter, I realized
that putting the stator side bearing on the outer ring instead of the
inner would improve the layout:
1. It would allow turning around the SDS coupling and decreasing the
motor width another .5" inches to 3.5".
2. Turning the SDS coupling around also simplifies alignment of the
rotor - the bolt heads are then on the right side to adjust easily in
3. It eliminates the need to drill some vent holes in the inner ring.
4. It eliminates the need for a special cover over the center hole in
the outer ring.
5. It makes the bearing more accessible for lubrication.
The down sides to the change are small:
1. The shaft is 1-1/2" longer.
2. A spacer about an inch long will be required on the shaft.
However, the longer shaft is still only five to six inches, and the
improve resistance to sideways shaft twisting forces.
With flat plate rotors instead of brake disk rotors, and
bearings on the outside, the motor is about as short as it can get
without going to extremes or changing the electromagnetic design. The
main body is 3-1/2" thick, still by 11-3/4" to 12" diameter. The rotor
is just 1.5" across, and the rotor with magnets is almost an inch
thick. What's left is useful for cooling air flow.
The coils are an inch, the magnets are 1/2", the gap
between them is over 1/2", and the rotor plate is almost 3/8", making
up 2-1/2". Then there's about 3/8" air space behind the rotor and two
3/8" end ring plates, adding another inch, total 3-1/2". The bearings
holders, and the heads of the bolts that hold it all together, stick
out a little farther.
I was very ready to slap a "final version" motor together
near the start of the month, but as of the 15th, Waterforce had only
cut my two big Weel motor pieces and not the five Hubcap motor pieces
including a flat rotor. Oh well... no shortage of other things to do!
When I've checked the fit and made sure the pieces don't need any
changes, I'll get 1/2 dozen of everything and afterwards not be waiting
on him until six motors are done.
Late in the month I gave an order for a couple of rotors
and plates to Victoria Waterjet in Langford, too. Langford is
increasingly hard to get to from Esquimalt during business hours, but I
might as well try them out too; they're there! Why have all the eggs in
one slow-moving basket?
Smaller Diameter, too
I was having trouble with epoxy sticking to the PVC outer
shells when casting the body parts. The reason the motors were
the specific diameter they were was that I could use the 11-3/4"
turquoise PVC culvert pipe for the outside of the mold. At the same
time, epoxy would ooze out the gap between the UHMW-PE "butcher block"
ring and the PVC shell, and also the PE was a little thin, and I had to
back it with plywood. On top of those things, I wanted to have three
molds so I could make all three body rings in one gooey epoxying
session instead of three separate sessions per motor. This is now the
most labourious part of making a motor.
For all these reasons, I bought some 1" thick ultra high
molecular weight polyethylene (UHMW-PE) 'butcher block' to make new
Looking at a motor, I decided it was about 1/2" bigger
around than it really needed to be. Not much, but I planned the new
molds to make 11-1/4" diameter parts instead of 11-3/4". The mold would
be routed out of the 1" pieces on the CNC drill/router as a 5/8" deep
"pan" with no holes or cracks in the bottom. It would still need a
piece of plywood reinforcing the bottom. This proved an advantage in
that the mold pieces were now 12" x 12" instead of 12.5 x 12.5": the
heavy PE is very expensive and Industrial Plastics only sells whole
square feet regardless. The extra material for the extra 1/2" x 1/2"
thus quadrupled the price for a single mold piece, and doubled it for
two or three pieces (and only by cutting some clever angles out of the
larger pieces). Now I'll get four pieces out of the piece I bought that
would have only made two.
I changed the center holes from 2-3/4" to 3". The 4"
center hole in the stator inner piece is unchanged. But the pan would
have a 2" "post stub" in the middle, and the desired taller 3" or 4"
diameter UHMW-PE post would have a 2" hollow in the base and fit onto
that. That gives the tall post of the desired height for stuffing the
PP fabric around, and it can be pulled out afterwards, providing a spot
at the center to get a chisel under the molded piece and pry it out of
The one remaining problem is that I have no tube to put
around the outside to stuff the PP fabric into, except perhaps to cut
down a piece(s) of the PVC pipe to make it a bit smaller. But perhaps
when the mold top ring is pushed all the way down into the pan, the PVC
ring can come off and be cleaned off separately, before the epoxy
hardens. A PE piece would be better.
I have enough pieces molded now for four of the slightly
larger diameter motors. The future ones will be a touch smaller and a
Bigger Bearings & Shafts
The axle of the motor with the first planetary gear to
connect to a car wheel had to be
1-1/16" on the gear end to match the inside diameter of the sun gear.
the 28th I took a 1" trailer axle, cut it to length, and turned down
the fat end on the lathe to that diameter, to fit the gear and a
1-1/16" I.D. trailer wheel bearing.
Owing to the forces involved plus the car wheel bumping
around, the bearing and shaft on the gear side would take considerable
loads, but since they were rated for the wheels of 2000 pound trailers,
surely they were big enough for the job?
But there was a hitch. The sun gear of the planetary gear
wouldn't fit through the bearing race or the hole for it in the end
plate of the motor. Nor could it be put on later, as the bolt holes
weren't accessible once it was installed. That meant the gear had to go
onto the axle first, slip the axle in from the outside, and then
put the bearing and the magnet rotor on. That in turn made it difficult
(though not impossible) to install and adjust the magnet rotor.
The sun gear just fits through a 1.375" bearing
race. So I'll probably continue to use the Pacific Trailers stub axles,
which are 1" at one end, and just over 1.375" at the other; easy to
turn down to that diameter for the bearing and a 1.375" SDS bushing. An
inch at the end gets turned down to 1-1/16" for the gear. The SDS
bushings to hold the rotor on are available for all these shaft sizes.
The larger bearing size means revising the metal end plate inner
diameters on the motor as well. (now
that I thought I had everything set up!)
The larger diameter won't add much weight to the
motor. The weight where the SDS bushing is - 1.5" of the 5" shaft -
remains the same since the larger axle diameter is compensated by a
in the bushing - it's all metal one way or the other. An inch at the
gear end needs to be turned to the diameter for the gear regardless,
and the stator end (about 2.5" long) remains 1" for the 1"
I'll use up the five 1" trailer axles I've already bought
before switching to uniform starting diameter shaft.
Hall Sensor Board
I completed the layout of the Magnet sensor board on
April first or second. It puts the Hall sensors in just the right
places and angles on one circuit board, simply screwed onto the inner
stator ring. When I got the boards back, I found I had neglected to
check the A1203 pinouts: they were Vcc,Gnd,Out, not Gnd,Vcc,Out, so I
had the power and ground backwards. As the board was so simple, I
simply connected the ground wire to Vcc and the Vcc wire to ground, and
crossed a couple of resistors for the motor temperature sensor. You
wouldn't even notice! Of course I corrected the layout for the next
A3938 V2 Motor Controller
Tristan was designing a new motor controller board and I
left it with him. He sent the finished layout and it was very good
except 1/2 inch wider, 2" instead of 1.5". This was understandable as
there were more components on the new board - filter resistors and
capacitors, test point pins, and a 5 volt power supply for external
peripherals. But it meant the chassis boxes would have to be 1/2 inch
thicker. Being a fussy person about such things, I decided I would try
my hand at shrinking it down again. I left out a couple of things that
we'd agreed to put on because I was having trouble routing the lines,
and then I added a 100uF filter capacitor and an additional .1uF in the
battery power line. As I think about it, although there's a dozen
capacitors on the busses at the mosfets, they go to "Vs" rather than to
the main ground, and it was foolish neglecting the PCB filters from
this spikey line in version one. However, it doesn't appear to be the
explanation for the
failures of the version 1 boards.
I also changed the header connectors to three, each with a
clearly defined function: there's now one 6 pin to the motor for hall
sensors and temperature sensor, an 8-pin for the basic controls, and a
9-pin for statuses and instrumentation. All have 5 volts power and
The controls header has the connections to the 'gas' pedal
potentiometer, on-off, forward-reverse, brake pedal switch and brake
pedal potentiometer. The last two of these are for regenerative or
dynamic braking, but they aren't used in the first version. ("Brake
pedal switch" should be connected to ground, as it is active high and
has a pull-up.)
The status header includes 5 volts power, the 3 magnet
sensors (from which may be derived RPM, speed, distance traveled,
direction and illegal sensor states/unplugged detection), battery
voltage divided by 10, motor current (1mV/A), motor temperature, and
the A3938's 'fault' pin status. You can hook anything to these signals
from no connection at all to a voltmeter to a multifunction
microcontroller run display with status and diagnostic system giving
MPH, mileage, state of charge, remaining driving range, overheat
With a combined system that connects to both the control
inputs and the status plug, one could introduce computerized
overcontrol of the system, without compromising the controller's
critical hardwired current limiting system, coil timing et al. Such a
system would probably make regenerative braking simple.
After starting in on making these motor controllers in
found brushless motor controllers were in fact available - mostly
smaller, but a few models seemed big enough. I had one
running by then, but more than once I've wondered if designing and
making them myself is a good use of my time and resources, or if I
should just be
buying controllers. But I ran into to a store clerk who said he had had
been part of several EV conversions using kits, and he said that
although they were costly, the controllers would fail after a while.
And evidently the well known line of controllers in the kits is made by
hand - "3 a month" when he was involved. Apparently they're not all
they might be, and hard to make as well. And then of course there's the
"false pride" factor: I wanted to make my own controllers because my
BCIT diploma is in electronics and I've created many successful
electronic designs... though almost none for 20 years, and they were
mostly digital and computer interface circuits.
My prototypes have blown up a lot of mosfets and chips and
have been a continuing source of trouble. But the troubles have been
and are being weeded out one at a
time as they rear their ugly heads, and with each improvement they
become more robust and reliable. The MC33033 version seems quite
reliable now, though I have the one in the car supplying reduced
currents to the motor for fear of losing it. Assuming the final
A3938 (or A3932)
Turquoise controllers work reliably, it seems possible they'll work
better than whatever else is available. That said, Canadian Electric
Vehicles says the controllers
they're using now work well unless they're blown up during
installation. I'm pleased that it's a "hard wired" circuit rather than
microcontroller programmed design. It won't have any timing glitches or
software bugs to cause unexpected troubles or failures on the road,
which seems to be a feature of at least some of the available
I completed the A3938 version 2 circuit board layout on
the 5th and e-mailed it, along with the magnet sensor board layout, to
AP Circuits on the 6th. I also sent the magnet sensors board to someone
in Vancouver who has a nice CNC machine good for circuit boards.
Unfortunately, my CNC drill router is probably too big and clunky for
any sort of
circuit boards, even simple ones. (Then again... what would happen if I
put a dremmel tool on it with a small router bit? Hmm...)
The finished boards arrived on the 11th. I put together a
controller the next day.
I also decided that I'd shrink down the wiring box that
the controller is a part of, from 10" long to 9", and from 6" wide to
4" or 5". As it's progressed, the components in that box have dropped
to just the main circuit breaker and a relay to turn the system on and
off from the car key. Other than that, it clamps the incoming wires,
has a big ground central bolt, and encloses everything. It no longer
needs to be very big, and space in a car is limited.
I didn't get a chance to test the controller until the
20th. It ran a motor for a brief time and then burned out. I
recalculated the blanking time capacitor and found I'd been using one
about 20 times too large. That's probably the trouble, although I can't
think why that would burn out the controller rather than mosfets. I
replaced the A3938, but those tiny surface mount chips are just SO hard
That one burned out almost at once too. This time, with
the reduced Ct capacitor size and the same Rt,
the frequency was 4x higher than the max, and probably that did it. It
was burned out in a different way than the previous ones: only the
oscillator quit running properly. I couldn't understand why Allegro
didn't put out app notes for the A3938, showing typical component
values with calculations and reasons therefor. All these costly
prototyping failures for silly, easily avoided reasons is a ______. On
the one hand, it's up to me, the designer, to double check everything,
but on the other, seeing a couple of sets of "typical values" from the
chip maker would doubtless have raised some red flags where mine were
notably different. If I wasn't so persistent - and if
I hadn't had some "pure luck" initial success showing the "gas pedal
like" operation, now months back - I
might well have given up and gone to some other chip from another
I decided to look again at allegro.com. I had originally
stumbled across the A3938 and designed the controller around it. But at
Allegro.com I recently discovered there's also an A3932 - an almost
identical chip with a couple of small differences (main difference:
it's half the price!), doubtless the first of the 'series'. Linked to
the A3932, but not to the A3938 (thanks a lot!), was an
application note for designing around the chip! It is obviously
applicable to both chips, but it wasn't
caught in any searches for the A3938 part number.
I wrote and the web manager says he's linked it now.
According to the web manager, the person who wrote that paper said it
was written for a lecture and wasn't a substitute for real app notes or
better datasheets. (Sounds like he wasn't very impressed with Allegro's
I did glean a a couple of vital details from that paper
that weren't mentioned in the A3938 datasheet: the chip was intended to
drive "up to 100 nanoCoulombs and beyond" of MOSFET gate charge. Since
the IRFP3206 MOSFET is typically 115 nC and there are two in parallel
(240 nC typical, 270 max), it becomes apparent why the A3938 gate drive
signals often seemed to be individually failing: the drives are
Furthermore, the app notes reminds that the gate signal
lines should be kept as short as possible, and (I probably knew this
but had forgotten), that the gate resistors should be as close as
possible to the gates.
I increased the gate resistors from 15 to 27 ohms. That
will make for slower switching slew rates and more heat in the MOSFETs,
but should cut the currents the drives have to supply virtually in
half. And I shrunk down the mosfet array, with one inch between
transistors on the heat sink bars instead of 1.5", which very
considerably shortened the gate wires to the outermost ones. The
controller plate is only 6" long now instead of 9". The motor power
wire terminal blocks had to be moved out in front of it, on an extended
base flange, since there's now no room at the side.
Another change after I thought I had everything all worked
out, this time to the motor controller & chassis dimensions!
New "shrunk" 6 inch wide motor controller layout with short gate
Four MOSFETs are under the (unfinished) PCB where there were three.
Wood block shows where heavy terminal block will sit.
The smaller size will do nothing good for heat dissipation from the
In all the planetary gear work, I haven't yet finished the
revised controller, but I have good hopes it'll finally work. The last
motor/planetary gear test on the car with the old MC33033 controller
shows it's badly needed.
Battery Voltage: 36-42 nominal?
Originally, I wired the three coils of each phase with 60
turns of #14 wire, intending the motors to run from 120 volts DC. Then
realizing that was creating a needless electrical hazard (not to
mention needing 10 batteries for any 'full voltage' test), I put the
coils in parallel instead of in series, so they would use three times
the current at one third the voltage - 40 volts. (Now I'm wiring 20-21
turns of #11 per coils and putting them in series again. Paralleling
these would make them good for 12-14 volt operation.)
Three 12 volts batteries gives 36 volts - close enough, I
Also I think even 48 volts nominal is starting to get a little high -
four batteries can be 54-58 volts when charging. It's getting close to
being a shock hazard, and the motor controller is only rated for 60
volts absolute max.
Now, making my own nickel-metal hydride batteries from dry
cells (and sometime my own chemistry batteries), I see no reason not to
make whatever voltage I please. I think
I'll add in a six volter and try out 42 nominal volts. That could also
be achieved with 7 golf cart (6 volt lead-acid... with sodium
sulfate) batteries. With the
same current, there's about another 750 watts available if the motor -
or the controller -
doesn't get too hot. And with the efficiencies hinted at by the low
idle currents I've been seeing, I don't think they will, at least not
The mosfets - and the A3938 motor controller - are only
for 60 volts, so counting spikes and noise and charging voltages up to
about 50 volts (PbPb or NiMH), 42 volts is probably about as
high as one should go with my controllers so as not to push the 60 volt
'absolute maximum' semiconductor specs and risk seeing it go up in
smoke. (I did use 48 volts in one test with the MC33033 based
controller with no adverse result.)
The Electric Weel Motor Project
The next pieces, the ring for the magnets and the stator
center, were cut at Waterforce.ca in Sydney by mid-month. I started to
realize that the best way to put them together would be the same way
I'm now doing the smaller motors: an enclosed motor with the bearings
in the end bells, and the giant magnet rotor attached by an SDS
coupling to the 2 inch shaft. If the Hubcap is perhaps more of a "cake"
the Weel would take on a real "pancake" shape, 28" diameter and still
just 4" thick.
However, the new motor controllers are still not working.
Not only are they badly needed for the Hubcap motors, it's almost
pointless to build this motor and not have the three controllers it
will need, so until those are working properly and there are enough
made, they have priority.
Two-piece 26" rotor (magnet positions outlined by waterjet!),
and stator center piece, with bearings and shaft.
The motor diameter is almost identical to the wheel/tire O.D. of the
truck it's to be installed in,
so it ain't a Hubcap motor to go on the wheel!
Planetary Gear Project
It seems people want the motors for vehicles (no
surprise), but I still don't have a working torque converter. With
gears, a Hubcap motor at about 4:1 gear ratio might
a car up to 50-60 Km/Hr for city driving. Highway
driving would have to
be done on gas, with the motors decoupled from the wheels to prevent
over-revving them. One
would have to stop and disconnect before hitting the highway.
Of course, my car
did move with the
direct drive 1 to 1 ratio. Could I be overestimating the amount of
torque multiplication that will be required? A 2 to 1 ratio would keep
the motor revs to 2000 at 100 Km/Hr. 3 to 1 - more likely to work -
might allow near highway speeds, even 80 Km/Hr (2400 RPM).
I finally decided to look
into planetary gears as an interim
measure. I really didn't want to do them. They are inferior to a
1. The fixed speed reduction ratio is a compromise. It works fine at
mid speeds, but it doesn't give
very good torque for starting the car moving from a stop, and the motor
and faster linearly with speed until it hits its maximum RPM, which
will define the top vehicle speed. With the torque converter the torque
and speed are optimized for any given speed and driving condition,
including outstanding start-up torque and moderate RPMs on the highway.
Theoretically, one could put a two or three speeds
transmission on the wheel to solve the basic problems, but in practice
I think it will be hard enough just to mount one gear with a fixed
2. The lubrication requirements are high. In gas car transmissions,
they sit in a bath of oil, but mounted out on the car wheel, it's a
At first I had decided to have a continuous
oil drip lubricating them, with a manual shut-off. In summer, cheap
vegetable oil is an eco-friendly way to go. Corn oil seems to stay
liquid in the fridge almost down to freezing. Now I've decided to try
just lots of grease first. I have two identical planetary gears: if the
first one in grease breaks down, I'll try the oil.
The gears turn at absolute speed depending on vehicle
speed. The torque converter was hopefully to only turn at a relative
speed - the speed
difference between the motor and the wheel, which is substantially
slower. Consequently, wear and lubrication requirements are much less.
But it may be (those designs having failed to perform well so far) that
I try a torque converter design that has sort of stator that doesn't
turn, then it will be more like the gear - also easier to design.
BUT planetary gears do WORK! Cars can start to be hybridized!
Any port in a storm! Losses
should be low - Having no oil bath eliminates most
of the fluid friction. If and when I get a working torque converter, it
the gear. That automatically and
rate of between around 10 or 15 to 1 and about 1.5 to 1 would be
any smaller car with one motor using the least
amount of electricity.
I was looking into planetary gears at a place on the web,
but the guy was slow answering e-mails and it dragged on without me
getting to place an order. The ones I first inquired about turned out
to be $475 - almost the price of my whole motor kit! I thought the
sizes seemed good, but the torque rating was actually about 3 times
what was needed, so I asked about smaller models. Only two suitable
looking models were under $400, at $215.
But earlier on the same day that I finally got those
had the idea to drop in on an auto transmission shop, taking with me
two pieces (of three) of a broken planetary gear I'd picked up from
curiosity in 2006 when I was doing the wave power stuff, just to show
what I was after.
The first shop referred me to a second shop. The guy there
immediately identified the gear as a Chrysler gear for a V6 engine.
Wow! He wasn't sure of the torque rating, but guessed around 150
foot-pounds. That seemed to be well over the requirement. Perfect! I
asked where one
might buy such things. "We have them." Wow, pay dirt! He showed me the
other pieces that went with what I had, and got on the phone and said
he could get me all the drive parts for a working, used transmission -
TWO planetary gears plus everything that went with them - for $109, and
have it there the next morning. Wow, pay dirt again!
He didn't know the reduction ratio, but said that each
planetary gear could do three ratios. If the inner part turned with the
outer casing held stationary it was one ratio, but if the inner part
was held stationary and the outer case turned (and was the output), it
was a different ratio. Once I had that digested, I forgot to ask
about the third ratio, but later I realized it would be with the
inside shaft held stationary and the inner and outer housings turning.
I picked up the gear set the next day (14th) and started
figuring out what would go where. Selecting the more suitable looking
of the two planetaries - the same one as the sample I'd already had -
by day's end, I had cut the sun gear in half with a zip disk (the two
ends went to the opposite planetaries) and figured out how to mount it
on the motor shaft, grinding slots for two 1/4" holding bolts that
would screw into the axle. The inside diameter, however, was 1-1/16",
so the 1" axle shafts were too small. I would turn down a trailer axle
I'd bought earlier that was 1.4" on the fat end.
The outer case with its inside ring gear would be affixed
to the motor.
The planets part - the output - I'd have to weld or bolt a
to to put the wheel drive pins into. Ironically, this meant that the
broken part of my original sample gear isn't needed - I had everything
I needed all along except the sun gear... and to know what to ask
for. I bought another sun gear and had two complete identical
gear sets: one for each motor on both rear wheels.
The gear ratio turned out to be about 2.8 to 1. That might
be enough. If not, with two
motors, that will be the equivalent of 5.6 times the torque of a single
motor (which did after all move the car, if only barely, in the October
2008 test). Earlier I was estimating 7x would be a good figure, but
is good enough. (A test at the end of the month suggested one motor
with a 2.8 ratio isn't good enough.) If it is, it is very helpful
that with 2.8 to 1
gears the car's top speed can likely be around 80 Km/Hr rather than 50,
60 or 70, revving the motor up to about 2240 RPM. That gets it
essentially onto the highway. And if perchance 4 to 1 or less works,
two motors at 2 to 1 would give full 100+ Km/Hr speed.
But I'm wondering if maybe one "double" Hubcap motor (20"
diameter, 10 KW) wouldn't be better: it would have 4x the torque of the
smaller motor even without a gear, and two would have 8x. But at that
point we're up to 20 KW of motor, and they'd have a rough time with a
flat tire, the bottom end hitting the road.
Wheel Plate turns wheel by pushing on the lug nuts. (1/4" mild
This was the first try at mounting the outer ring gear on a flange.
The black piece inside is slippery delrin/acetal plastic for the planet
gear assembly to rub on.
(Yes, I had a hard time cutting the inside circle.)
Ring gear mounted on motor end ring.
Motor shaft turns sun gear (center one), 1.062" I.D., so needs
1-1/16th" axle turned on lathe.
I switched flanges to this one, cut by CNC waterjet.
The planet gear carrier in place. Note the threaded holes I made
near the outsides to hold the wheel thrust plate.
Another piece of delrin is enclosed for sun gear to rub against.
Completed outer assembly april 27th.
Ring gear is stationary, sun gear on motor shaft turns planet gear
assembly, ratio 2.8 to 1.
Planet gear assembly is connected to lug nuts on wheel by plate, and
tentatively held against motor (since nothing else is holding it) by a
spring from the plate to the wheel. (Might be a good place for some
more delrin between ring gear and outer face of carrier to retain
carrier - and seal it up a bit.)
Note the very short distance from the motor to the car wheel - it won't
stick out as far as the rear view mirror.
The lug nuts and bolts already take the torque of the car engine and
I'm less sure about these 1/4 inch bolts holding the plate onto the
planet gear carrier.
The sun gear on the axle,
and 'dust cover' on the motor, April 29th.
Fitting the motor & gear to the car,
thrust plate at lug nuts.
Marking up for fitting motor spring mountings.
Sticks out farther than rear view mirror - one inch thinner motor will
be an asset.
(Truck for Electric Weel motor project is behind.)
Spinning up the motor with 2.8 to 1 gear on 30th. Jacked up, it
On the ground, the car only twitched - but then it was only getting 1/2
current from the motor controller.
Lubrication: Oil Drip... Lots of Grease... or Nylon Planet Gears?
Transmission gears usually sit in the enclosed
transmission in an oil bath. If this one needs an oil drip for
lubrication, that's okay for testing and demonstrations, and for
real zealots, but one can just see it en masse: car
up daily on busy streets because the oil ran out or was left turned
off. Oil slicks causing accidents on the road. Shortages of vegetable
oils at the grocery.
But once I got started, it
dawned on me that gears can be made of nylon (or other plastic such as
acetal/delrin - there's even a "nyla-steel" made for doing gears), and
nylon gears don't require lubrication or are "self lubricating". It is
preferred that nylon gears mesh with metal gears. In the planetary gear
as configured for this job, only the planet gears spin around fixed
and the other gears contact only with the planet gears. So if one could
replace the metal planet gears with nylon ones, it would be perfect,
and constantly dripping oil
wouldn't be required. An occasional greasing would do fine.
Then it dawned on me that helical gears might be made in
standard sizes, and one might actually be able to find the right gears,
ready-made of nylon somewhere, if one knew what to ask for and where to
look. Perhaps even a planet gear carrier complete with the nylon gears,
ready to just pop in.
I went on the web, found some plastic gear places, and
made a few e-mail inquiries. They went unanswered, or the answer wasn't
I also found out that gears are (or can be) made on
something called a "gear hobber". I saw a picture, and some ideas for a
cheap, single purpose "gear hobber" entered my mind. I could use one of
the metal gears themselves, using the teeth as detents to rotate and
line up the nylon piece to just the right angle and place to duplicate
the teeth. Then mount a dremel tool or an angle grinder on a stand with
a pivot to make the cuts. Sort of like a fancy key cutter that follows
the shape of the original key.
But that would be a last resort! If the metal gears will
work okay just with grease, they'll be fine, and I should forget about
Otherwise, I can use it even
with oil dripping for testing and demos for some months before I run
of patience looking for a source of ready-made nylon planetary gears -
or at least individual planet gears.
Either just greasing the gears, or else plastic planet
gears, will make the whole idea truly practical. Otherwise, turning
oil drips on and off before and after driving... and forgetting to
do so... will be unpopular and unreliable.
Torque Converter Project
Doing the planetary
gear work has made me think perhaps I should change tack with the
converter design: If it were to have a stationary component, like the
stationary outer case of the planetary gears (or the stator of a fluid
torque converter), it could be made as a sort of variable ratio
planetary gear. It would then be a positive action drive rather than
the oscillating masses design.
For me, the biggest attraction of the "all live parts"
design was that everything would spin together and other than that the
force transferring parts would be moving no faster on the highway than
when starting out from a stop: That minimizes lubrication requirements.
It also seemed to have the most slack construction standards - extreme
precision wasn't required, whereas gear must mesh exactly.
On the other hand, I have not had any success making the
yet, and any converter that works is better than fussing around
with planetary gears, with their fixed
ratios forcing use of bigger (or more) motors with more torque.
The torque ratios of a design that I'm now thinking of now
might range from perhaps 6-10 to 1, to 2-3 to 1. That's less dramatic
range than an oscillating masses converter, but it meets the
requirements. One thing that makes it seem more feasible now is that I
know that Waterforce could cut straight gears (though not helical) with
exact teeth to any
specifications I supply - I've seen some made at his shop.
In this design, the planet gears would mesh with the
ring as usual. But they would have an "X"
or "*" on top of each, eg four or five arms. The motor side has drive
pins that hit the
inner arm of the "X" as they go by instead of a sun gear. The drive
pins are pulled towards
the axle by a spring. In their innermost position, they just miss the
tip of an arm of an "X". At low speed, the pin on the slightly extended
spring will reach an "X" only if the arm is pointed almost straight
in, so it will only contact some of the arms. As the motor turns faster
and faster, the drive pins move outwards, and hit more towards the
center of the "X", hitting all the "X"es and turning them farther as
they go by. The more planet gear "X"es that are hit, and the farther
are turned each time, the lower the drive ratio.
If I up-scale the size, say to the full 12" instead of 4", and use big
nylon planet gears, it might not need more than greasing once in a
It seems likely I'll want to refine that idea some before
attempting to building
anything. In the meantime, I'm giving planetary
gears a try.
Turquoise Battery Project
Manganese versus Vanadium?
I bought four carbon electrode rods plus 1/2 a pound of
battery grade MnO2 mixed with graphite powder for only $2... two
packages of two D cells at the dollar store. It would be more
convenient if they just put the materials in small jars, but then
they'd probably charge much more!
I thought I'd look more closely at the electrochemical
reactions of a couple of elements. Chromium has a soluble ion form,
similar to zinc and cadmium that so shortens the cycle life of cells
made with them. So much for chromium! But on inspecting vanadium I
found that it had a negatrode reaction that looked similar to manganese
iron, nickel, copper, etc). In alkali it was no better than iron, which
is cheap - but its voltage went up slightly with acidity instead of
down, and so in salt
solution it was probably just a slightly lower voltage than manganese.
In addition, the atomic weight of V is 51 versus 55 for Mn, so it would
have a few more amp-hours per kilogram, 1052 versus 975, and the VO
discharge in preference to V(OH)2 is also lighter (cell needs less
If V was substituted for Mn, the (probably) slightly lower
voltage would make it a little easier to prevent hydrogen gas
generation and the overall energy density should be similar.
Plus, vanadium also seemed to have potentially workable
positrode reactions, "vanadiate"(?) similar to the permanganate but
electrons. Was that worth exploring?
Then I looked up the price of vanadium oxide. At the
pottery supply it seemed to be 20 times the price of manganese, indeed
more than any other "top row" metal except cobalt! And then there's the
dollar store price of Mn. So much for vanadium!
discharging for 24 hours (into a 28 ohm load and ending at .3 volts -
the highest figure yet), it seems the
battery was taking several hours charging to gradually
get back up to about 2 volts, and a whole day at least to be really
well charged again. It takes more current at a higher voltage to charge
than to discharge, but it was behaving more like a real battery. Was
the dopant helping?
I decided to try another osmium/acetaldehyde/cellophane
separator film, this time dipping a paintbush down and stirring to make
sure a decent bit of the trace of Os in the acetaldehyde in the test
tube was ending up in the film. This time if there wasn't enough
osmium, it wouldn't be because the densest of all metals had settled to
the bottom of the test tube and I was wicking up liquid from the top.
If there was further but not "night and day" improvement,
more powder could be added to the test tube for the next try. In fact
however, no improvement was evident.
A few days later I added more electrolyte and smeared in
some more MnO2+graphite.
In the quest for better conductivity, I've compacted
electrodes and compacted graphite sheets. But then I put them together
in the battery, where they are only nominally pressed together. It
occurs to me that I should be compacting them together to ensure good
In fact, as I thought about it, I became sure that this
was a big part of the answer. But
there was no guarantee that the electrode material would stay stuck to
the graphite when it was removed from the compactor. I decided I'd try
perforating the sheet with lots of little holes, and allow the
electrode material to fill the holes. That would give them at least
some sort of bond, and increase the surface area of contact between
But it's a bit tricky when
I need to torch/sinter the positrode after compaction and the graphite
would burn. Perhaps I'll try a little steel bezel to protect the edge
the graphite but not the edge of the electrode.
If that doesn't work, I could compact the electrode alone,
sinter it, then re-compact it with the graphite sheet.
Another idea would be to texture the graphite sheets.
Hopefully even without strong compaction there'd be electrode briquette
contact points at high spots all over the sheet. I thought of the
textured ABS plastic sheets. I cut one to size and put it into the
compactor with a graphite sheet. By gosh, the graphite sheet came out
looking just like the plastic! I decided to just reopen the present
battery (again, sigh) and try it on the accessible negatrode and see if
it made any notable difference to the current and voltage. It seemed to
help a little.
Graphite sheets. L: with punched holes; C: compacted against textured
plastic; R: plain cleaned with hexadecane and scotchbrite
Textured sheet with punched holes.
This sheet had been used a couple of times and started to fall apart.
When I made an electrode on it, I didn't put in sufficient graphite
powder and the resistance
was too high because of that. It didn't look like it would stand any
Later I tried simply
roughing a graphite sheet surface up
with coarse sandpaper. That seemed little or no better than texturing.
Surface of graphite sheet roughed up with #40 sandpaper.
I think next time I'll try washing a square of carbon
(graphite) fibre with boiling hexadecane (outside this time - it really
stinks) and using it as a conductive mat, compacting the electrode
around it. That might connect better to the electrode powders, but
instead I'm wondering how well it'll connect to the terminal post.
Aha Moment: Could Nickel be charging above oxygen overvoltage?
On the 15th I thought about the high self discharge. Every
cell I make with salt electrolyte
seems to have horrible self discharge. I thought the Mn negatrodes must
be verging on being too high a voltage, but various measures hadn't
fixed it. I tried using iron for a lower
voltage negative in case it was my Mn hegatrodes, but even that only
helped a little. Was there something intrinsically wrong with using
salt as an electrolyte? But the old standard dry cell uses salt, albeit
it uses ammonium chloride instead of potassium chloride. What then... just
It had to be something... what about the oxygen generation
voltage at the positive electrode? We know nickel charges properly in
alkaline solution at about +.5 volts. We also know that lead charges
properly at +1.7 volts in acid solution. But we also know that these
are just under the wire: when the temperature hits about 40ºC the
nickel alkaline electrode starts to bubble oxygen, and lead acid cells
do so notoriously on any overcharge. The addition of
manganese oxide increases oxygen overpotential of nickel electrodes...
in alkaline solution.
We might estimate
the oxygen overvoltage at about +1.1 volts for neutral solution,
and the nickel reactions as being about 1.0 volts. The Mn should raise
the oxygen overvoltage a bit more. These figures and assumptions, along
with the fact that nickel works in alkaline solution, led me to assume
everything was proportional and nickel would work fine in salt
solution. But they aren't really very reassuring on close
examination: they're only estimates - the midpoints between alkali and
acid. What if the voltage shift is non-linear, and the nickel voltage
is a bit
higher or the oxygen a bit lower? Or what if the manganese reactions
are a little higher voltage than expected, or Mn doesn't raise nickel's
oxygen overvoltage in neutral salt solution? The batteries do put out
about 2.2 volts rather than 2.0. Or maybe oxygen generation starts a
little lower in KCl than in some
One thing that is known is that the self discharge of
every cell I've made using salt solution has been awful. What if it's
because the positrode reaction voltages are just at or even slightly
above the oxygen overvoltage instead of just below?
One simple experiment would be to put a battery in the
refrigerator, then (if that didn't work) the freezer, and see if the
self discharge slowed markedly. CSA/DREO (and others) only had trouble
production in their Ni-Cd satellite batteries when the temperature rose
above about 40ºC. Maybe troubles in salt would stop at a threshold
temperature, perhaps below
5ºC, or -5º?
I set a table next to the fridge in the lab so the battery
could be inside and the charger and DVM outside with just a couple of
wires going in. I had been doing ongoing tests, and they would simply
be continued and any improvements noted.
With the cell in the fridge at 2ºC, I figured I was
onto something the next morning (16th). The voltage with the charge on
was over 2.1 (Ni/Mn-Fe cell), whereas it had never quite hit 2.0 volts
wasn't being dragged down as much. When the charge was removed, the
self discharge was still far too high to work. It seemed somewhat
slower, but it didn't seem it had crossed any "threshold" temperature
where it would simply work fine.
Next test was in the fridge's freezer at -6.5ºC. Hopefully there
was enough salt in the electrolyte to prevent it from freezing. (The
NiMHs I've been getting are rated to -10.) After it had charged a
while, I turned on the DVM and it was good for a laugh. It read about
2-1/2 volts, and when I took it off charge, it still said over 2
volts... on a 1.6(?) volt cell. This must mean that some trace additive
element must have charged up that would have been too high voltage to
do so at room temperature - probably the calcium, or maybe the
antimony. It seemed to have high self discharge again... but this time
from 2+ volts downwards towards where it was supposed to be.
I put a 10 ohm load on it, and the voltage dropped to .6.
Evidently the electrolyte wasn't working very well - probably half
frozen. (I wonder how much of my cells' high internal resistance is
due to poor electrolyte conductance normally?)
After a minute or two of load, it stopped going up to 2
volts open circuit and went only to 1.66. The self discharge this time
(of the main ingredients) was definitely much lower - it stayed above
1.6 volts for several hours instead of several minutes, and was still
1.45 after 12 hours. The threshold was crossed.
It seems likely that oxygen overvoltage is the culprit, so
the next thing to do was try to figure out how to raise the overvoltage
so it would work at higher temperatures.
I found a paper talking about using higher numbered rare
earth elements (in KOH) to raise it, and I started thinking about the
lanthanum-monel mix in bean sauce I did in the first year of this
project. Nickel oxidizes in positrodes in salt solution (unlike in
strong alkali wherein it's inert - the key attraction to producing
alkaline chemistries). That was why I couldn't get any batteries to
work at all back then -- the "+" terminals corroded away no matter what
metal I made them of including nickel. (I didn't try gold, platinum...)
About the only higher rare earth element not mentioned was dysprosium,
the only one I have some of. Evidently samarium is likely the best.
The metallic nickel in the monel would thus charge to
NiOOH and become the active electrode element, and the lanthanum is
fairly likely to raise the oxygen
overvoltage enough so it will work properly.
The copper will also oxidize, to a copper oxide as the
hydroxide (Cu(OH)2) is, like zinc hydroxide, evidently not very stable
and it will change to CuO or Cu2O.
That will add no energy, but both Cu2O and CuO are lower impedance
semiconductors, and in solid solution with the NiOOH it should improve
conductivity substantially and make the NiOOH more available.
I could probably add manganese, too, and get better
amp-hours, and graphite, and get best conductivity. Manganese is also
supposed to raise the oxygen overvoltage of nickel electrodes... at
least in alkali.
I originally thought monel would give the positrode
fantastic conductivity since it's normally so corrosion resistant in
salt water, but
since it in fact oxidizes readily in the battery positrode, that never
did work. (...except before I started charging the cell - it did look
great then!) Adding traces of cobalt oxide and maybe zinc oxide
(I'm not very sold on the zinc, though its conductivity is good), could
help conductivity. IIRC there's already cobalt in the mix. Wow: the
very stuff I started with in 2008, plus graphite powder (and maybe Mn,
Sb, Ca, Zn, Sm oxides to improve it), might actually work great! Did I
had good stuff in the first place - workable though not working
the way I had envisioned it? In that case the key problems were just
the corroding metal terminals and the poor conductivity without
I've put in ALL the ingredients and steps here except making the case.
The recipe has become too complex to try to remember everything while
working, so that was initially partly to actually refer to
when I made it myself, and then because it had a fair chance of being a
So, the positrode for the next cell would be:
* Carbon rod terminal (salvaged from "D" dry cell).
* Backed by a conductive graphite sheet (boiled in hexadecane and
sanded with #40 sandpaper to raise the grain and texture it.)
* 25g of the original mix: monel powder (Ni:Cu alloy), La(OH)3, 1%
Co2O3, baked in bean sauce. (Note: next time, I think I'll just torch
it after making it, and never mind pre-burning the mix. But I have
quite a bit of that mix already made & burned.)
* 10g MnO2/graphite mix - salvaged from dry cells
* 1% Sb4O6 - oops, a big clump went in. I spooned some out. - .6g? I
meant to use .35 g.
* 2g Sunlight and sufficient water for stiff paste.
* 16g more graphite powder. This was determined by tamping
down the wetted powder with the pestle and testing resistance. I added
more graphite 3 times. When it was down to around 10 ohms I stopped.
* a bit more water.
It got a lot fluffier with all the graphite powder, and 25g of the mix,
about half of it, looked like a good amount.
* Compacted it (25g) - with the roughened graphite sheet.
Hopefully they are well connected together.
The electrode was about 3 - 3.5mm thick.
* painted on a thin layer of Ca(OH)2 to raise oxygen
* A second painting: of zirconium silicate to block any
stray MnO4- ions.
* Dried it in the oven at 110ºc for an hour, then torched
it just about 10 seconds to sinter and harden. (If it's not dry, it
will explode from steam
pressure when it's torched.)
The separator would be:
* A piece of cellophane painted with acetaldehyde that's been doped
with osmium powder.
* A piece of Arches watercolour paper. This wraps up the sides to form
a little paper "tray" for the negatrode, to
ensure there's no contact between the electrode materials.
The negatrode would be:
* Salvaged D cell carbon rod terminal
* Graphite sheet as above (sometime I may get brave and try metal
structures again in the negatrode -- should work [Cu2O(s)
+ H2O <=> 2 Cu(s)
+ 2 OH− [@ −0.360v], so in the -1v negatrode it
should stay 'charged' to metal] -- but not this time.)
1% Sb4O6 (.2 g) - .25 g. I put it in first this time so I
could pour back or dump out any excess.
* 25 g of salvaged MnO2/graphite mix. There was a lump
looked like (was) 1/2 a D cell. It was very well compacted and read
about 100 ohms. I decided to try and get it lower.
* 2g Sunlight + sufficient water for stiff paste
* 10 g additional graphite powder. Even after that, mostly the readings
were in the 100s of ohms. It was in fact too damp to tamp down very
hard, and the meter leeds sunk in easily. Some water oozed out of the
* 25 g of this mix was compacted with its graphite sheet. It came out
about 4mm thick.
* Eggwhite painted on (absorbs in), baked in oven. (Although, the
eggwhite was already freeze-dried - it had been in the freezer for
months and all the moisture was gone.)
The usual KCl plus some sodium borate (borax) in distilled water.
This cell seemed so promising I spent a day on the 25th to
The graphite sheets came apart from both electrodes. Oh
well!, maybe punch some holes in the graphite next time - or try the
carbon fibre. I pushed them
firmly together in the
The cell started off at -.32 volts... reverse charged. In
effect, I'd made it backwards.
The "+" side was mostly monel, the nickel metal being a
negative electrode form. That would have to charge to Ni(OH)2, the
positive discharged form, and then to NiOOH (or maybe NiO2?), the
charged form. The MnO2 on the "+" side is a "+" charge, but with a
lower voltage than the KMnO4 in the charged cell. The
"-" side, on the other hand, was MnO2, again an "overdischarged" form
for a negatrode. It would first have to charge to the regular
discharged form, Mn(OH)2, and then to the charged metallic form.
This small reverse voltage drove over 100mA through a 1
ohm resistor. After 5 minutes it was over 60mA, and after 20 minutes,
it was still 50mA. It seemed like a good sign! Two hours later, it was
still putting out 16, and it recovered to -100mV in a few minutes. Then
I started charging it, in the right direction.
It occurred to me a while later that both sides of the
battery would be using up water during the initial "precharge":
MnO2 -> Mn(OH)2 on the "-" side and
Ni -> Ni(OH)2, Cu -> Cu2O or CuO on the "+".
That meant that after a while I would have to unscrew all
the screws, open it and add water - and how many times? ugh!
I added water twice, and it charged over a period of about
four days. It still had very high self discharge.
A Working Battery... by charging it in reverse!
Well... it had started out with a negative voltage, and it
put out 100mA from just a -.3 V starting level. What would it do if I
charged it backwards? Although the main ingredients could theoretically
work that way around, this seemed contrary to reason since all the
additives to increase overvoltages were arranged the other way.
However, I tried it... and it worked! After
some time charging it was at 1.1 volts. I took the leeds off, and it
soon stopped discharging at about 1 volt. This probably meant it was
charged to MnO4 at +.5 volts and Ni metal at -.5 volts. Overnight it
got up to 1.65 volts, and when charge was removed, it was still 1.5
volts after an hour. In fact, it would hold almost 1.5 volts for
several hours. When given a load for a minute or two, it would drop in
voltage but when the load was removed it would recover to pretty much
where it had started from. The current capacity is low with an internal
resistance of evidently about 3 ohms, but it's a battery!
Voltages with loads (once relatively stable):
no load: 1.5 V
51 ohms, 28 mA: 1.4 V
11 ohms, 100 mA: 1.1 V
1 ohm, 400 mA: .4 V
In May some amp-hours tests will be made - and some
calculations of what they ought to be to compare with.
So what was the chemistry? Obviously the positive side
(formerly negative) was manganese - there was no other major ingredient
in it. It had a choice of charging to MnO2 at +.5 volts (standard dry
cell level), or KMnO4 at +1 volt. The negative side had the monel
(nickel:copper) and manganese. The copper would turn metallic quickly -
it doesn't have much potential. The nickel would charge to perhaps -.5
volts. The manganese would charge to around -1.3 volts.
The most likely choice, given that it stops right about
1.5 volts, is that the + side is KMnO4 and the minus is Ni, and that
the Mn in the negative won't hold a charge because its voltage is
definitely too high without eggwhite.
That would mean that in previous cells it was really the
manganese in the negatrode at -1.3 volts that was causing the self
discharge, as initially suspected. On the other hand, the cell with a
lower voltage iron negatrode also self discharged, albeit somewhat more
slowly. I attributed the slower discharge to the lower voltage of the
cell overall, but with the culprit 'obviously' not being the negative
side. Now I suspect it was both negatives - the manganese with its high
voltage, and the iron too, an element which, though it doesn't corrode
in alkali (hence nickel-iron alkaline batteries), doesn't fare well in
salt water -- as is well known.
So for the moment I'm assuming that in the positive side,
manganese works at +1 volts as KMnO4 -- at least with added eggwhite,
and nickel works in the negative after all -- at least as constituted,
from monel with lanthanum hydroxide in bean sauce, flamed, and with
added manganese oxide or hydroxide and graphite powder. The best form
to supply manganese+ in might then actually be as KMnO4, while adding
the monel as metal powder on the minus side. Thus the battery would be
made as a pre-charged cell.
Even if nothing else fundamentally improves this, it could
still make the most economical, long life rechargeable batteries. They
wouldn't be radically different from standard dry cells, but the energy
of charging the manganese from dioxide to permanganate is much higher:
the reaction voltage is +1 volt instead of +.5, and discharging to
dioxide it moves three electrons per molecule instead of one, so the
amp hours per kilogram will be greater. It's possible well made cells
could hit 200 watt-hours per kilogram even at a nominal 1.3 or 1.4 volt
A potential close to 2 volts may well be attainable,
though the list of suitable negatrode elements is looking pretty small.
There may well be some way to get the manganese negatrode working -
it's evidently out by just a small amount. This would be the best
solution, and if I can think of any ideas, I'll try them.
Otherwise, I'll probably try that vanadium (~-1V) after
all. It looks like (all else being equal) it should be about .3 volts
lower than the manganese negative, which, with eggwhite added, is
likely to make it just enough less that it will stay charged. That
should make 2 volt open circuit cells, or about 1.8 V nominal in use
rather than 1.2, 1.3 or 1.4.
I phoned the pottery supply and while vanadium oxide (V2O5)
costs much more than manganese oxide (especially from old or new dry
cells!), it's probably not more than nickel oxide (NiO) after all, 10$
for a quarter pound, though I haven't compared on a metals content
basis or checked other sources or quantities. The store did, however,
put their one bag of it aside for me.