[Oeva-list] Ev Batteries

[Paul Wallace]

I'm just about to pick up a set of 96 100ah Sky Energy Li Ion cells from 
EV Components.  I am also getting the BMS that they offer, which allows 
them to extend a 2 year warranty on the cells.  The total package cost 
is just under $15k.  The people at EV Components and their customers are 
seem to be having good results now with both the Sky Energy and the 
Thundersky cells.  With the 2 year warranty, I feel that I should be 
covered for any infancy failures.

I wasn't able to get IE to open the web page you sent this morning. 
I'll try again later with my Mac.

Paul Wallace

Graunke, Gary wrote:
> Looking at the Sandia report, these batteries should be great in an EV. 
> It doesn’t answer the question of quality of manufacturing, but covers 
> everything else.
> 
> Our experience with A123’s LiFePO4 was that 1-2% have a higher 
> self-discharge rate, but they are otherwise very consistent and meet and 
> exceed specs in every way.
> 
> These also meet or exceed specs in every way, according to the authors.
> 
>  
> 
> To deal with these kind of variations, I would suggest the 12V 40AH to 
> 80AH batteries (maybe even the 120AH if you have a pickup truck), so you 
> have 4 to 12 cells in parallel.
> 
> The 26 to 34 lb batteries are easy to life by hand if you need to work 
> on them. The AH depends on your desired range and/or $ you have to invest.
> 
>  
> 
> The low temperature performance is better than lead-acid as well, losing 
> only 25% at freezing (about our low in Portland) or 34% if you live in 
> Bend. The high power of the cells helps the low temperature performance, 
> however, compared to lead, and you still can put in battery heaters or 
> an insulated battery box if this is a concern. An insulated battery box 
> would also help if you have a catastrophic cell failure with 160C 
> temperatures. (Always vent the box to the outside (not cabin) for this 
> reason, though it is not critical).
> 
> There is no high temperature concern (life with most other batteries!).
> 
>  
> 
> Buying the batteries in this package makes it difficult (if not 
> impractical) to do individual cell group management, but it sure is 
> convenient!  However, it may well be that monitoring the battery voltage 
> at 12V will be good enough (that is what we are forced to do with lead 
> acid batteries in any case). (The issue is that one should slow 
> down/shut off the charger when a cell reaches maximum voltage to avoid 
> overcharging it). The self-discharge rates on a cell mean that you may 
> want to charge individual cells (or cell groups if they are in parallel) 
> to keep them in balance. I do this manually right now every 10 months or 
> so with A123 cells, but will eventually put in equalizers to do this 
> continuously.
> 
>  
> 
> Bottom line—I would have used batteries like this in my Insight had they 
> been available 3 years ago. Let us know how much they want for them.
> 
>  
> 
> Other sources are thunder sky (though they have not met specs in their 
> early offerings), peak battery (K2). I am running K2 batteries in my 
> plug-in Prius from EEtrex—they have less (but still adequate) power than 
> A123’s, but 30% more energy per same size and weight cell.
> 
>  
> 
> It is important to assess the quality of the batteries. It helps to know 
> someone who has been using them, but this is difficult with new 
> batteries. The Sandia report is very helpful in this regard, but there 
> is always a concern that they “cherry-picked” the cells that they sent 
> for testing (rather than a random sample from their production).
> 
>  
> 
> Keep us informed with your progress!  
> 
>  
> 
> Gary
> 
>  
> 
> ------------------------------------------------------------------------
> 
> *From:* oeva-list-bounces at oeva.org [mailto:oeva-list-bounces at oeva.org] 
> *On Behalf Of *Rob Russo
> *Sent:* Friday, October 09, 2009 6:45 PM
> *To:* oeva-list at oeva.org
> *Subject:* [Oeva-list] Ev Batteries
> 
>  
> 
> Thanks to all who responded. 
> 
> I guess my main concern and probably the first decision I have to make 
> is the type and voltage of the battery pack. I want to avoid lead acid 
> batteries because it seems counterintuitive to add all that weight to 
> such a light vehicle.
> 
> Is this battery pack practical for my application?: 
> http://www.lifebatt.com/HPSpacks.asp . Are there any alternative sources 
> for this type of battery?
> 
>  
> 
> Thanks,
> 
> -Rob
> 
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