# [EVDL] A123 Balancing with TL431, leakage current



## EVDL List (Jul 27, 2007)

Hi Lee etc,

Thanks for the heads up on the leakage current depleting the charge on the A123's over 8 months at 400uA. (Sorry I can't reply to the original email content on this hotmail - webmail)

I looked at the TL431 data sheet and it shows reference current of 2 uA (not 400) and a off-state cathode current of .1 ua however I had a 10k pot drawing 330ua at 3.3V on the A123 2.3ah cell. So I need to use a max resistance pot that the TL431 will tolerate, 100k maybe 1M OR put a telcom relay on my shunt regulators. In this UPS application I'm just holding at 3.45V so I don't have to worry about cycling *but* if this thing sits on the shelf for months the leakage current (if not paid attention to) could kill the battery. I don't think it would go to 0 volts though as the battery voltage drops the circuit draws even less current but I'll retest to minimize it or put in a 14 contact relay. I though of using optos & fets but that's getting messy with additional componentry.

Had fun E-boating & sailing with Chip, next week-end in Minn with Lee's & BEST kids E-race. Then onto Power of DC at the end of May. This is certainly an EV month.

Have a renewable energy day,
Mark
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