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Model Forum / Radio Controlled / Air Models / March 2009LiPo voltage drop
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 rr What is the "C" rating of each battery??? >What is the "C" rating of each battery??? 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. Sounds like a bad cell to me. Dan >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 [quoted text clipped - 15 lines] > Thanks much > rr > 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 [quoted text clipped - 16 lines] > rr > yes, its f.cked. Yes, sounds like on bad cell. That battery could be very dangerous. Careful! Did you get it at the LHS? Hopefully he will let you return it since you haven't even put it in a plane or anything yet. >> 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 [quoted text clipped - 17 lines] >> > yes, its f.cked. > 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 > rr 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.. Trefor |
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