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Re: [EVDL] Lithium Battery Balancers: Fatal Flaw; Monitoring - reliability

PS With secondary monitoring required incase one cell goes out of bounds, how do you flag it as a balancer component failure (vs just being done with charge)? It still seams like a lot of attracted complexity to me for a production vehicle. We hobbiests may personally monitor but I wonder how all this would be reliable in high volume (EV's).



From: [email protected]
To: [email protected]
Subject: Lithium Battery Balancers: Fatal Flaw
Date: Tue, 12 Oct 2010 11:31:24 -0400




Hi Folk's,

All the lithium battery balancers I've seen (and the one's I use on my LiFePO4 T-Sky's www.evalbum.com/2749 ) have one thing in common, if one dies that battery/cell either goes way high or low (depending on the mode of failure) destroying the cell. So you need to secondarily with *seperate* monitor the cells *also* with a bunch of wires going everywhere like with my scanner www.evdl.org/lib/mh/ (and balancer OV shunt clamp) but to another level of shutting down the charger if anyone of the balancer's or cell voltage goes high. This attracted complexity is why at work we decided to go back to NiMH (and probably why Toyota-Prius & Honda-Insight did too).

I'll probably use LiFePO4 batteries in my www.evalbum.com/1273 when my Ni-Cads go bad (hate the weight and crappy handling of lead) but they require baby sitting and wonder what the long term reliability will be if we see a bunch of new EV's using this complex balancing/monitoring circuitry in production. It would be nice if there was a LiFePO4 or some chemistry that's light and didn't require picky balancing (behaves like lead without the weight) maintaining the KIS principle.

Have a balanced day,
Mark
www.reevadiy.org community service renewable energy & EV's

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