Rear motor power, battery options and charging.

[lesdit]

I am planning to add some rear wheel power to my car. For batteries I plan on using the Honda packs as a
source of cheap D cell strings. Issues are : Is it OK to discharge many strings of D cells that are wired in parallel ?
The Etek motor will see about 100 amps at about 36 volts being fed into a Sevcon brushless controller. I went
brushless because 1/4 inch brush wear in 300 miles, as measured by Mike, does not seem very serviceable to me.

Charging is another issue. So far the solution seems to be charging each string with isolated dc-dc converters is an option.
For recovering regenerative energy, maybe charging Etek pack via power from the 12v car system, with what, 25 amps ?
No need to get regen power from the Etek, the cars regen back to the IMA battery will suffice.
Couple Etek to rear wheel: Looks like spring needs to be relocated. I'll have the guy working on my race 240z suspension/driveline take
a look at that. I'm thinking U- Jointed PTO shaft to a wheel stub axle.
A lot of work. I have to swap in the low miles motor and tranny first!
-Les

[uhtrinity]

Discharging in parallel isn't supposed to be an issue, but charging can be. I hope to do a test tomorrow by connecting my 2 packs in parallel and then test for EV range. If all goes well I should be able to go about 4 miles if the car can use all the capacity.

The things I hope to test / verify:
1. Can two packs be discharged, or be recharged (limited) in parallel.
2. How will this effect the amp count? By running the second battery's line outside of the current meter mounted on the output side of the battery will the car see the extra discharge / charge. If not this extra capacity should work transparently.
3. What are the limits of charging in parallel? From what I understand, the problem with charging in parallel has to do with with the voltage vs capacity graph of NiMH. If you exceed the peak voltage you overcharge, and can damage / destroy the battery cells. Imbalanced packs, or packs that reach full charge to soon can make this happen.



What I hope to do is take both temperature and voltage readings as the packs discharge, while also keeping track of what the soc meter shows, as well as the mima current leds. At full charge in the car I have been seeing about 167 volts, but using the Triton II full capacity per subpack runs at about 8.65 volts, or 173 volts for the whole pack. That comes out to 6 volts across the whole pack that isn't used and might be enough of a safety buffer. From what I have seen the subpacks also maintain the same voltages to within a few 1/100th of a volt, and the imbalance relates to capacity. If it works like I expect, the soc meter and mima leds should show if one battery is discharging into the other. As safeguards both batteries will have the stock 100 amp fuses, as well as the on / off switches.

Is it possible that since the Insight uses limited capacity, that two packs may be able to be safely charged by the car? I suspect this might possible since the peak voltage should never be met, and a safeguard could be added, just as using a combination of the PTC strips and the high current relay. If the battery temps get too high the relay kicks in (or more appropriately off). The same approach could be used for plugin charging, while leaving battery usage functional for extended trips.

Sorry for the ramble, but these are some of the ideas I have been toying with since picking up the Civic pack.

[lesdit]

Rambles are good.

I take it you want to run the extra 144 volt pack as extra power for the IMA to use.
One way to get extra energy into the main IMA pack is to run an higher voltage pack ( 06 pack ) and have a PWM switching circuit
that throttles the energy from the higher voltage pack into the main pack. Perhaps at 25 Khz.
A simple micro controller could be programmed with
how much and when this extra charge is applied. The stock IMA would think that the main pack just keeps it's charge that
much longer. This wouldn't work is the IMA algorithm is measuring Amp Hours also, as it would probably fault out.
Charging stratagy would be much harder, obviously.

In my scenario I guess it's the charging that is the hardest part. I would use at least 8 strings of cells ( two 04 packs rewired )

Q: on MIMA systems, how long can you power the IMA motor for at, say 4KW, before it heats up and blows ? Is it an issue if you use
a battery of 3X capacity ?
If it's OK with the extra power, I'd rather use the IMA motor , not let it sit unenergized for most of it's time.
-Les

[uhtrinity]

The stock IMA motor is liquid cooled, but if you mount one elsewhere you may have to have some kind of cooling system.

My main intent is to be able to make better use of PIMA, essentially run IMA more aggressively for a longer period of time, and use plugin charging.

[Willie Williford]

"Liquid Cooled".?

Explain more.

Willie

[lesdit]

Is it true that IMA cuts back power to 7KW after a short period of time, perhaps to prevent IMA motor
failure? What are ramifications of heavy assist with 3X the battery of stock car ? Unexplored territory, perhaps ?
-Les

[Mike Dabrowski 2000]

UH trinity.
You should at least leave the fuse in the second pack circuit. where will the two packs tie together?
Lesdit,
my 48V e-tek draws 200 A, and I could use more power, my 36V golf cart can draw more than 100A.

I just found out about this company:
http://www.kellycontroller.com/
They have some nice prices, and a lot of selection.

$450 for an e-tec sized BL motor
http://www.kellycontroller.com/mot/Brus ... oller.html

The rear suspension set up with the spare tire well and springs, will need nearly a complete rebuild if you expect to get a "U- Jointed PTO shaft to a wheel stub axle " and a motor and mount under there.
Good luck.
Willie
The IMA motor is bolted to the engine block which is water cooled, so there should be some heat sinking from the IMA to the block.
I suspect that the reduction in assist peak power that the car does is more for battery issues than motor cooling.

[lesdit]

The Kelly makes trapezoidal waveforms , some searches reveal that this does not work well
with the etek. I should call them, I guess. The Sevcon make sinusoidal waveforms.
Maybe I should skip the 'good deal' on the 36 volt limited sevcon controller for $350, because I won't be able to get
the power I would like.
Mike, why are you using the etek 5th wheel instead of just powering the IMA motor more ? Maybe only to run with ICE off
and not spinning at all ? Just curious. I'd rather go with your MIMA system and throw a bunch of extra pack into the car if
the Honda IMA motor can withstand the duty cycle. From what I saw on your site, the IMA motor coils don't look that well thermally
coupled to the rest of the engine, so I'd fear overheating them.
Has *anybody* run the IMA moter at full assist for 10 or 20 minutes ??
-Les

[Mike Dabrowski 2000]

I have drained the pack from full to empty in one assist cycle at 100A. I have no way to measure the coil temperature, but saw the batteries heat up by 10 degrees in the cycle.

The IMA rotor has impellers, so at higher rpm it acts like a fan, and the coils are wound on a heavy laminated iron core that is bolted to the aluminum frame that is bolted to the block. Not great heat sink to be sure, but better than nothing.

I run the IMA stock motor a lot more when I turn on the boost converter, mostly on highway runs. I only have 16.5A of boost. 20 to 25A would be much better.

I put the e-wheel on the car because I wanted a pure EV mode, as I do a lot of slow around town stop and go,which is better with engine off.

Once I get my IMA motor bearings and mount, so the motor can run stand alone, I will be able to mount a temp probe and do some power and thermal test.
What will stop my progress is that I don't have a spare IMA power electronics driver box .
Anyone got one in their garage?

[lesdit]

I have the complete electronics package from a 06 civic battery cask , you are welcome to any of that, if it helps.

So in my case, where I am not usually in stop and go, you would recommend pumping more energy through the IMA motor?
That would simplify everything, for sure .

-Les