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Extra Battery, How to Integrate with 24kWh Traction Battery?

Posted: Tue Oct 25, 2011 10:56 pm
by TonyWilliams
What would be the best way to connect an additional battery pack to the existing main battery? Would hacking the ChaDeMo connection be the most logical access to feed DC power?

If I put a 12kWh pack together, with it's own BMS and charger, can each cell just be in series, thereby matching the 393.5v / 4.1v per cell? Is there a more advantageous voltage?

Re: Extra Battery, How to Integrate with 24kWh Traction Batt

Posted: Wed Oct 26, 2011 12:45 am
by DougMarker
Don't use the CHAdeMO connector. Just tap into the big wires coming out of the traction battery. The motor only cares about voltage, and I think that goes for all the other electronics too, so if you pile up enough batteries to get to 403 volts, it should work fine. Since I don't know what I'm talking about, let me know if it works, 'cause if it does I'm gonna do it too.

Re: Extra Battery, How to Integrate with 24kWh Traction Batt

Posted: Wed Oct 26, 2011 7:56 am
by garygid
MAJOR CAUTION WARNING

The LEAF's Battery Management System (BMS) might have enough checks to make the integration difficult or even impossible. It might think that it has a HV "leak", or ... ???.

However, even if the BMS does not object, and the car appears to work:

1. The normal cell-pair equalization process might be compromized.

2. The Low-Cell detection (to stop driving) would not include the "booster" Pack, possibly damaging cells there.

3. The High-cell detection (to stop Charging or Regen) would not protect the "booster" pack, possibly damaging cells there.

4. Connecting a 400v "booster" Pack to a half-depleated (perhaps 350v) main Pack would generally cause HUGE CURRENTS unless there was a DC-to-DC converter to act as a "charger" between the two battery packs.

No, in my opinion, there is NOT an easy, safe way to "toss in" a parallel "booster" Pack.

One might be able to "charge" 10A or so into the partially-depleated Main Pack, but the car control COULD object to something as simple as finding current flowing INTO the Traction Pack when driving and NOT doing Regen.

CAUTION:
Experinents by untrained persons can destroy the LEAF, cause a fire or explosion, or even injure or kill a person.

Re: Extra Battery, How to Integrate with 24kWh Traction Batt

Posted: Wed Oct 26, 2011 8:24 am
by charlestonleafer
I'm really surprised that none of the companies that make kits to extend the EV rage for Prii have made a kit for the Leaf yet. Is a Leaf system more complicated than a hybrid? I would think it would be simpler? I really think that if people will pay 5-10k to extend the EV range of their hybrid, others would certainly pay the same to extend the range of there EV. Has anyone even tried? Completely agree with garygid, it should definitely be a trained individual/company who attempts this, but please someone try!!!!

Re: Extra Battery, How to Integrate with 24kWh Traction Batt

Posted: Wed Oct 26, 2011 8:30 am
by TonyWilliams
I'll try not to stick my finger in the high voltage bits :)

So, how about if the car were stopped, turned off, and the booster battery was connected through the two high voltage cables used for the ChaDeMo connector, and the booster battery pack never exceeded 393.5 volts, can you foresee a problem with that?

Obviously, a three way switch to the battery, selecting ChaDeMo or booster battery. Now, with that simple addition, I can't imagine that the car would think anything but that it's being charged.

Having said that, obviously it's to our advantage to know the protocols and safety features of the ChaDeMo that may inhibit or regulate charging.

Re: Extra Battery, How to Integrate with 24kWh Traction Batt

Posted: Wed Oct 26, 2011 8:38 am
by TonyWilliams
charlestonleafer wrote: I really think that if people will pay 5-10k to extend the EV range of their hybrid, others would certainly pay the same to extend the range of there EV. Has anyone even tried?


I saw a 12kWh lithium manganese battery pack in a brand new Prius; very small package, 40 mile no-gas range. That's what I want in my LEAF.

Re: Extra Battery, How to Integrate with 24kWh Traction Batt

Posted: Wed Oct 26, 2011 8:39 am
by charlestonleafer
Or what if you kept the batteries completely separate and just made a switch between the 2 packs. Almost like having the 2nd as a "reserve". If it were switched right after the batteries, before it got to any electronics, it seems like it could work?

Re: Extra Battery, How to Integrate with 24kWh Traction Batt

Posted: Wed Oct 26, 2011 10:57 am
by highcountryrider
Doesn't the LEAF BMS monitor each cell? I don't think this is a simple as
putting in reserve pack and a big DPDT switch. :?

Re: Extra Battery, How to Integrate with 24kWh Traction Batt

Posted: Wed Oct 26, 2011 11:28 am
by DarkStar
How do the plug-in Prius kits work? Seems to be a parallel arrangement and the software modifications are to allow extended speed EV mode...

Re: Extra Battery, How to Integrate with 24kWh Traction Batt

Posted: Wed Oct 26, 2011 11:33 am
by mwalsh
You may have missed it in the LEAF Limo thread, but I asked the folks from Liberty Electric if they'd give consideration to marketing the extender pack they're developing for the limo, if aftermarket demand was sufficient and any technical limitations could be overcome. They seemed quite willing to consider the possibility.