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Old Jan 20, 2008, 02:24 AM
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Troubleshooting "dead" lipo

What does a dead lipo act like, and what could I have done to kill it?

I have a new 800 mah Polyquest 3s1p I bought a couple months ago, it was one of a few. A month ago I started using them, and charged them up with no incident. I have used some of them 1 or 2 times each, charging them back up after use. Today, I put one in my plane, and there seemed to be no charge at all, like a completely dead battery. It has been charged and run once or twice, or charged and never run. I put it on the charger, and the green light did not budge from green (it should turn red to indicate charging). The leads and connector seem to look fine and feel fine. I tried some of the other batteries and they worked fine with charger and plane. I could test the continuity between the balance plug and the wire to it, and the charge/power plug and the lead connecting it, to see if a wire is not connecting well to a plug, but I think it's unlikely both plugs could go bad at once. Any suggestions on how I can determine what's up with this battery?

Thanks much,
Jim
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Old Jan 20, 2008, 04:25 AM
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Do you have a volt meter? If so what is the voltage at the discharge plug?

Glen
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Old Jan 20, 2008, 02:31 PM
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only a slow discharge capacity test will diagnose a bad pack and bad cells
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Old Jan 20, 2008, 05:38 PM
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You need to get a volt meter to check voltage across the balance tabs for cell voltages and check the main tab for pack voltage.

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Old Jan 21, 2008, 02:47 PM
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Quote:
Originally Posted by hall woo
only a slow discharge capacity test will diagnose a bad pack and bad cells

How do you do that? Do you need a power analyzer?

I will check the main and balance plugs with my VOM later today...and report back. Thanks all.

jim
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Old Jan 21, 2008, 03:16 PM
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no, just a watts up meter and voltage protector
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Old Jan 21, 2008, 07:26 PM
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Quote:
Originally Posted by hall woo
no, just a watts up meter and voltage protector

Thanks Hall Woo. What do you mean by a voltage protector?

Jim
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Old Jan 22, 2008, 03:38 AM
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At the charge plug the voltage is 12.63. The voltage between the two farthest apart leads on the balance plug is also 12.64. The voltage between each lead and the adjacent lead is 4.21. This sounds to me like it's OK, but that's not based on any expertise.

Should I just try to use it again in the morning and see if it still acts dead? At least being fully charged would explain why the light on the charger stayed green instead of going to red. Doesn't explain why the plane acted like no battery was connected though.

Thanks,
Jim
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Old Jan 22, 2008, 07:27 AM
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Could be bad connector/bad solder joint on the pack since the other packs worked normally. Try re-soldering the pack connector.


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Old Jan 22, 2008, 07:50 AM
Master of 1 point landing
Naperville, IL
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SOunds like a broken lead to me. Check the wires in the pack, sounds like one came off the battery tab/tap.
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Old Jan 22, 2008, 11:52 AM
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Quote:
Originally Posted by cloud-9
Thanks Hall Woo. What do you mean by a voltage protector?

Jim
fma voltage guard
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Old Jan 22, 2008, 12:22 PM
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Hi again, I read the voltages from the connectors, that is, by touching the probes to the two deans tabs in the female holes, and on the balance plug, by touching the silver connections in the plug. Doesn't this eliminate a problem with the connection between leads and plug or leads and battery? But it also makes everything more perplexing. Maybe it's intermittent, and that day the leads were not connecting well. Resoldering seems like a good next step if the problem happens when I connect it to the battery again.

Jim
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Old Jan 22, 2008, 01:46 PM
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Jim, my bet is your deans has a bad connection. Knockoffs are more known for this, I have had this 3 times in the past year so I am over them.
Replace the packs Deans and re-try. It should work then.

Rick
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Old Jan 22, 2008, 01:47 PM
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Sure does Jim - try wiggling the wires while measuring the V but be careful not to short the pack while doing that.

There have been reports of "bad' imitation Deans connectors--they make contact if pulled slightly apart but fail to make contact when fully inserted. A search should find those threads. Were your Deans real or just like's?
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Old Jan 22, 2008, 01:56 PM
Will fly for food
Maryland
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If you leave them fully charged for too long of time, you can get very little capacity as the cell degrade from that.
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