A123 module


Some prototyping netted 91kw of output from my truck recently. The acceleration was unbelievable. That’s still an 80% improvement. The pack is sagging more than normal right now. So I’m correcting that as of now. I suspect that would be worth a few more kw. Looking forward to 100kw soon as the pack gets updated and the R & D progresses.

The data sheets say the factory igbt’s are rated at 400 amps. Almost there now. If I can keep the pack above 250vdc at 400 amps, then I’ll be at 100kw.

I have had an igbt/hv buss redesign going. Might have to put more priority into that since the factory igbt’s are nearly at their max current rating. Although for maybe only 10-15 seconds at a time, 400 amps may not be a threat to their longevity.

With the A123 prototype modules doing fine, a full pack would have such low impedance that 100kw would be easy to hit. Maybe too easy. Going to build about 12 more A123 modules soon.

My A123 modules got a beating at a combat robotics contest recently. They held
up fine. They were charged with a BMS on each cell. Discharge rates overlapped
my truck. These cells saw far more G-forces than normal. But I needed some
testing on the structural side of the design to make sure nothing stupid
occurred. The spot welds were of particular interest. The owner uses A123’s in
his robot. Now he’s sending 100 more for more packs to be made. Sweet. This time
however he has a different module layout he wants to try.

I used nickel as the conductor since copper is apparently next to impossible to
weld with a CD welder. I was told this and didn’t believe it. Then I tried to
for 3 days. Nope. Even as fancy as my CD welder is. Nickel is universal for cell
assembly. But not only is copper cheaper, it also is a better high current
conductor. That’s also what makes it harder to weld. It basically has no
resistance. Since I’m making over 70kw now, I have to make sure a module can
pass 100kw for the future (fingers crossed). If copper ever gets used, I’ll have
to buy/make an inverter type welder.

I just won’t be satisfied until I can spin tires on dry pavement at will!

The 312v (405v max) AC motor control system in my truck is very energy
efficient. It’s only 70kw right now. But it will be 90kw here shortly. It has
the capacity to handle way over 100kw.

I don’t have to cram very much of a pack into this vehicle to get excellent
range. If I put in a 160ah set of Thundersky cells, my range would be 256 miles.
But then I have to put up with all of the cold voltage sag as well as the sheer
volume that this pack would take up. Works for some, just not for me.

Speed is electronically limited to 72mph. That also assumes I leave the
transmission locked in 2nd gear. It’s a 5 speed manual with overdrive. Adding a
shifter makes the top speed math go to some insane top speed. Or as ACP does,
remove all of the unused spinning mass in the form of gears and syncros for yet
more of an increase in efficiency.

Something I keep forgetting to explain. The cells themselves will only weight
154lbs. They completely fit in well under 1/2 the battery box.

The 7.36 kwh pack I’m building will take my truck 36 miles at it’s current
efficiency of 200wh/mi at 4000lbs. My estimate of a 15% increase in efficiency
from losing 600 lbs, will put the range at 42 miles at 175wh/mi at 3400lbs. On
only 50 amps the truck goes 60mph. There is an owner of a truck just like mine
with a 19.2kwh Thundersky pack. He went 112 miles on a charge. That’s about 171
wh/mi. But his cells weigh 550 lbs. That’s 400 lbs more than my A123 cells. It’s
feasible that my truck could end up with a 50 miles range off of the tiny A123
pack. Since the camber on the front end was finally just now set to zero, there
could be some additional increase in efficiency. I have yet to block the grille
and add the coroplast to the chassis underside to clean up some of the
aerodynamics. Those are standard features on all ACP vehicles, old and new. All
I need for my driving requirements is 15 miles of range. With 36+ miles of range
my cycle life will be close to forever.

I will pick up some cobalt 18650 cells for spot welding and testing. After all,
since the safest chemistry available can currently be set on fire so easily, it
just makes sense to try them. Their smaller size would make for an even lighter
pack. It’s just takes some mechanical and thermal engineering to make this work.
It’s just not that difficult.

I wonder if the laser welder I used back in 80’s is available surplus somewhere?
I use to spot weld nickel ‘flags’ to stainless wire. Not unlike materials for
cell module construction.

Gasoline is $3.79/gal down the street! Wow! We’re on our way to $4/gal and it’s not even close to Memorial day. Oil today was down to 96.50/barrel. Man am I glad this truck runs. The timing for making the A123 modules is pretty good.

I wonder if it’s even possible to spot weld aluminum with my spot welder? It is not as conductive as copper, but is far less expensive. Copper has at least tripled in the last couple of years. So I will start with trying to spot weld some aluminum foil from the kitchen and see how that goes. It’s cheap and easy to use for proving the concept, one way or the other. I will still be trying to spot weld braid as well.