Jack_K

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.

kdunlap

My Feedback: (12)

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?

Jack_K

You're correct. I was thinking of LiFe for some reason when I said 3.3v.

Jack_K

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.

mushia

Good luck, bro.

Jack_K

With what?