What's going on with this battery? - RC Groups
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May 28, 2002, 08:12 AM
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die fleidermaus's Avatar

What's going on with this battery?


I use four different battery packs when I go out to fly.
Three of them work great, but one pack never seems to work right.

When I use the bad pack, the motor will run about 5 seconds and then it stops completely. After about one second it comes back on again. If I manage to keep it in the air it will continue this routine many times. When it is squirting out electrical snot it has plenty of power.

What is likely wrong here? Is there a way to test this battery? What do I check? Can I check individual cells without unsoldering them? About the only tool I have is a digital vom.

The pack gets evenly warm during charging and the voltage never checks very low, although I know that can be misleading.

1,000 mah nicd, 8 cells
sp 400 motor
Zagi (Aveox) esc
Feather receiver
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May 28, 2002, 09:06 AM
Registered User
tekochip's Avatar
The best test is to put the pack under load with a small resistor, if you have one, and then measure the voltage on each cell. You'll probably find one or two that are low, or even reversed (polarity in wrong direction).

If you don't have a high power resistor you can use a bunch of small onew in parallel, or just leave the resistor in a cup of water to keep it cool
May 28, 2002, 11:37 AM
Registered User
My thought is to check the conector on the battery,i had a battery the same with a bad connector and that done the same,the battery sounds allright as when it works it works...i think my battery didn't charge properly with the bad connector either so i cut it off and soldered a new one on and it is now fine.
Jun 30, 2002, 01:36 AM
Registered User
I would guess it has a bad cell.

Measureing each cell individually with your VOM, under load, should isolate the flaky cell.

Also check connector for bad continuity etc.

It isn't magic, if it doesn't work, either a cell is bad or the connector is.

From symptoms, I'd bet on one bad cell. Remember, the other 3 work fine. Maybe comparing readings between good pack and bad one whould help find problem.

You aren't using Tamiya connectors are you?
They're not suitable for E flight, bad continuity.

Dave