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Is this a bad battery?

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Old 07-16-2017, 08:53 AM
  #1
Jack_K
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Default Is this a bad battery?

I have a 3500 mAh 3 cell LiPo pack. I fully charged it and let it rest and cool over night. I then did a discharge to storage voltage (3.3 volts per cell according to my charger) at 0.5 amps. A 3.5 amp/hour battery should last 7 hours at 1/2 amp discharge rate.

The charger said it took 108 minutes or 1.8 hours. So, 1.8 hours at 0.5 amp is only 0.9 amp/hours. That's roughly 1/4 of what it should be. Should I assume the battery is bad or the charger lies?

The charger is an iMax B6AC.
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Old 07-16-2017, 11:48 AM
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Couple of things. 3.3 V is not storage charge, it is close to the low end limit of a lipo which is 3.2V. So, first I would reset my storage charge to 3.85v/cell. Next, realize that you are not discharging the battery to 0 mah. You are taking your battery down to roughly 80% of the 3500. So, your would still have 700 mah in the pack. What is important is how many volts per cell the charger says. If your battery is 4.2v/cell then you are fully charged. That's the most important number. What did you get?
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Old 07-16-2017, 12:25 PM
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Quote:
Originally Posted by kdunlap View Post
Couple of things. 3.3 V is not storage charge, it is close to the low end limit of a lipo which is 3.2V. So, first I would reset my storage charge to 3.85v/cell. Next, realize that you are not discharging the battery to 0 mah. You are taking your battery down to roughly 80% of the 3500. So, your would still have 700 mah in the pack. What is important is how many volts per cell the charger says. If your battery is 4.2v/cell then you are fully charged. That's the most important number. What did you get?
You're correct. I was thinking of LiFe for some reason when I said 3.3v.
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Old 07-16-2017, 01:01 PM
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Yes, the battery was balance charged to 4.2 volts per cell before the discharge cycle.

So I was grossly mistaken concerning what was happening. In reality the battery was not discharged to 100% of its capacity, but only discharged to 60% (3.85 volts per cell) of its capacity in 108 minutes. That means the discharge used 40% of the battery's capacity in 108 minutes. In order to discharge the battery 100%, it would have to discharge 2-1/2 as long (100 / 40 = 2.5) or 108 x 2.5 = 270 minutes. 270 minutes is 4-1/2 hours. That's only 65% of the calculated maximum time of 7 hours.

So I have to assume the battery is only good for about 2300 mAh capacity. Kind of disappointing, but the battery was given to me, so what the heck.
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Old 07-19-2017, 12:54 AM
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Good luck, bro.
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Old 07-19-2017, 06:29 AM
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Good luck, bro.
With what?
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