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Old Jul 19, 2007, 12:26 AM
Registered User
Tennessee
Joined Jan 2007
239 Posts
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Can you check lipo balance with a DVM?

I'm getting better at flying my Helli and instead of down time consisting of rebuilding after crashes; I simply re-charge my lipos. My focus and concern now is that the lipos are taken care of properly to provide the maximum life expectancy.

The Lipos I use are 3 cell 11.1V 1250mAh. The measured voltage after a charge is around 12.5V and I have quite a few cycles on these batteries. (should have kept a log of cycles)

My current assumption is that the 4 wires leading to the charger will provide me with the individual voltage of each cell. I've measured the voltage beginning with one test lead of the DVM to ground and incrementing the other to the next lead of the battery.

The results of the first battery are as followed:

4.16V 8.34V 12.5V

My DVM auto corrects for polarity so after measuring the first two leads I checked the second two wires then the final two. The results were respectively 4.16V, 4.17V, 4.17V for a total of 12.5V. Again my "assumptions" lead me to believe this battery is balanced, the charger gives no faults and it works perfectly.

The second battery reads: 4.08V, 8.18V and 12.12V (4.08V,4.09V,3.93V) This battery will charge without any faults and works OK...appears to be very slightly "puffed" on one side but this could be the tubing around the Lipo.

I'm perplexed by the following battery...it's a 3 cell 11.1V 1000mAh Lipo reading 4.13V ,8.24V ,12.36V (4.13V, 4.10V, 4.12V) 12.35 output....."not fully charged". This Lipo has no physical damage and appears to be balanced but the charger gives an error when attempting to charge it. The variation of voltage doesnt seem that significant to me but then again I don't know if my current method of measurement is accurate or my understanding of balancing is adequate.

Thanks,

Mike
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Old Jul 19, 2007, 01:07 AM
Reduce the drama...
rick.benjamin's Avatar
USA, OR, Damascus
Joined Apr 2004
4,044 Posts
Hi Mike;
You are measuring correctly.
Only if it interests you, keep a log on each battery. I don't.
Fly battery 3 down a bit and then see if the charger likes it.
Battery 2 may be a bit unbalanced. Maybe consider a balancer purchase.
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Old Jul 19, 2007, 01:53 AM
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United States, WA, Puyallup
Joined Oct 2004
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Battery #2 - what are the cell voltages shortly after charging?

Bill
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Old Jul 19, 2007, 09:48 AM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
21,107 Posts
"Bad" batteries lose voltage after charging. Pack 3? What is the error message? If you can, measure the capacity of that pack.

Pack 2 needs balancing. Try to keep the cells within +-.03V
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Old Jul 29, 2007, 10:41 PM
Registered User
Tennessee
Joined Jan 2007
239 Posts
Battery 3 is fine now.....flew it down and it charges perfectly. I "assumed" that after setting for a few weeks it needed charging but the voltage was already close to what the charger saw as max. It appears the batteries don't loose much voltage over time but what about the ability to deliver current? It seems a fresh charge always gives better performance.

I definately need to get a balancer as well as a new and better charger.

Thanks for the input.

Mike
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