LiPo voltage drop

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I got 2 1,800-mAh 3-cell LiPos the other day, one with a Parkzone
foamie I bought to replace one I totaled and the other off the shelf
of the LHS. I charged both then realized the new plane was missing
parts so I decided to discharge both to 11 volts because they'd
probably be unused for a few weeks (I'm not looking to start the "how
to store LiPos" discussion again -- last time was pretty thorough).
Anyway, I discharge by attaching a 12-watt 13.8 volt automotive lamp
with a voltmeter in parallel and watching while compensating for the
drop from the lamp.
One battery discharged normally. The other dropped a bit, then went
immediately to about 6.5 volts. Couldn't miss it -- the bulb went
quite dim.
I tried the questionable battery again, and it did the same, dropping
suddenly to about 7 volts.
My question, obviously, is Do I have a bad battery? Seems to me the
sudden drop is one cell going virtually dead. But I'm new to all this
and pretty ignorant. Any suggestions?
Thanks much

Reply to
tired bob
It's 1 for charge, 15 for discharge. Instructions on battery say to charge at no more than 1.75 amps, so I charge at 1.5. It's a balancing charger that comes with the plane and battery, supplied by Parkzone. Batteries are identical.
Reply to
Tired Bob
Sounds like it. If you're careful, you can measure each cell with a voltmeter. Access it at the balance socket. I had a cell go bad on a 3 cell lipo. It was an end cell. Gave it to my mate, who chopped off the dud, and is still using the 2-cell battery..
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