Chinese LiFePO4 goes pretty cheap, but that's not the end of it. He'd also need at least a BMS, and probably a new charger. (With some electronics background, he might be able to hack up a way for the BMS to control the C- car charger.)
David Nelson via EV wrote:
I don't understand why so many people keep insisting on this.
In this case, the ComutaCar charger is *not* voltage regulated, nor current limited, nor is there any shut-off timer. It is nothing but a big transformer and rectifier.
The ComutaCar also had a contactor controller. There is no current limit, nor any undervoltage shutdown.
It also sounded like this would be the purchaser's first EV. So no experience to rely on.
Lithiums would be an invitation for disaster in this environment. If you put lithium cells in this car, you'd also have to change the charger and controller. A BMS is also essential, because you can't depend on the car or the owner to do any monitoring or limiting.
I started with a cell level BMS and finally took them off. In 5 weeks it will have been 4 years ago and well over 12k miles since my pack was last balanced. The only thing I have is a digital version of Lee Hart's Batt-bridge and I charge to 69.1V for a 20 cell pack or 3.455Vpc. This charges my pack to 98-99% SOC. I finally quit checking the voltage balance at the end of charge every week and went to checking it monthly until I got bored of that and now I'm only checking it once every 6 months. As of today I have 20,552 miles on the pack.
That's great! I'm glad the Batt-Bridge has helped. With it, you will at least know if a cell gets out of balance (though it won't tell you which cell it is).
You were also fortunate to get a good set of cells that were pretty well matched. Not everyone is that lucky. The cells I've gotten to test (Thundersky, CALB, SBS) have not at all well matched.
A BMS should be looked at like the circuit breakers in your house. They aren't needed at all, until there's a problem. Then, the circuit breakers are all that's keeping you from destroying your house!
-- The greatest pleasure in life is to create something that wasn't there before. -- Roy Spence -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
