Lithium-Ion Batteries

[Ronbo]

How expensive was the volt battery? Did you get a rebuilt or a junkyard?

[Nuke-E]

It was from a junk yard. Out the door, I was at $2100. The car was a 2012, with 46k miles on it.

 

I measured each cell's voltage and all were within 0.01V. And testing so far suggests no real degradation in capacity. As far as I know, Volt batteries from GM are not much more, but you have to have them install it in a vehicle and surrender the old one.

 

I can say that a full charge delivered in 1 hour nets no noticeable change in cell temperatures. Heating/cooling the pack will only be for longevity, not safety.

 

I'm pretty sure it's going to end up being cheaper than AGMs all-in for equivalent capacity. I'm actually working on writing up more detail waiting for the ball to drop.

[Ronbo]

I was looking at this site. $2347 no core required for a reman battery.

http://www.gmpartsonline.net/parts/2012/Chevrolet/Volt/Base/?siteid=215055&vehicleid=407591&section=HYBRID%20COMPONENTS

[Nuke-E]

Ron,

 

That's one that I've seen discussed on the electric car forums--several have tried ordering, only to have orders cancelled when they didn't have the old battery to turn in. If one could be bought for that price, it's obviously a great deal with warranty and all. Some have speculated that GM is actually spending significantly more to produce the pack, selling them cheap to reduce fears about replacement after the car's warranty ends.

[Ronbo]

I am probably a year away from starting my lithium battery. I am still waiting on more info from yours. What are you doing for a bms? Are you building your own or purchasing components from one of the companies?

[Daveh]

Nuke, Have you seen any depleted Volt battereis for sale so you can turn it in and get the new one?

[Nuke-E]

Nope. Consensus seems to be that they're way over-designed, and failures have been incredibly rare. If you look at GM's advertised capacity, it has increased a few times without changing the battery pack--they were very conservative at first, and gradually changed the software in the cars to allow deeper discharge. I bought the second one I looked at. Either one would have been fine, but the first place wanted a $400 core charge.

 

As far as a BMS, the tentative plan is to use the Volt's system. There has been some progress in talking to the modules mounted on top of each cell bank--the hope is that by taking that route, all of GM's balancing algorithms and fault detection are retained. GM says the system isn't used very much, and I'm pretty sure it's overkill given the low charge/discharge rates in RV use, so if it can't be made to work I'm going to rely on occasionally manually checking cell voltages until I get a feel for what kind of variation is normal without balancing, and use high and low voltage and temperature disconnects to protect the pack. There are plenty of these packs in EV use with no monitoring system. The pack may degrade faster, but for RV use that's probably not a big deal.