New LiPo for X8 has swelled after just a few charges

My 2014 X8 originally came with two of the Tiger Power 6000 mAh 4S batteries, and I’ve probably gone through 24 cycles each on them. I purchased another battery from 3DR a couple of months ago, and it has only had 4 cycles so far.

Due to a personal injury on August 29th, I had not touched the X8, and the batteries had been left in the case, all at a full state of charge.

Yesterday, I pulled it out and checked the charge on them. The two older ones were at about 4.11V, and the cells still balanced within 0.1V of each other. The newer one had a higher state of charge, about 4.14, also balanced, but I noticed as soon as I pulled it out of the slot that it had swelled a bit.

I measured with a caliper, and while my old batteries are 41mm in height (including the velcro backing), the new one is now 45mm at the center. The bulge is squishy and feels almost like an air pocket.

I ran one of the old batteries and the new battery through test flights, and both drained fine. The flight took the new (bulgy) one down to 15.1V, and the old one down to 14.9V. Both were comfortably warm to the touch immediately after the flight and the swelling had not changed.

I left the new battery in my LiPo bag on the tile bathroom floor overnight with a fire extinguisher nearby just to be safe, but as I expected, it did not change in the slightest.

So. What is up with it!? Is this much swelling acceptable? Could it be defective? Could it possibly be due to sitting at a 16.6V full charge for three weeks? If so, why would it not affect the other two which were charged and stored identically?

I’ve always tried to be vigilant with my LiPos because I’ve heeded the warnings about them. This is my first experience with one swelling at all, so I’m hoping some of you with more experience can help me properly gauge my reaction.

-Daniel

You should not store at full charge.
Nor deep discharge, which also damages batteries

[quote=“Andre-K”]You should not store at full charge.
Nor deep discharge, which also damages batteries[/quote]

Thank you Andre. I definitely understand that they should not be stored at full charge. Please believe that if I could have avoided being in an auto accident and being laid up for a few weeks I would have been very happy to be flying the X8 or at the very least discharging the batteries to a storage state instead.

Unfortunately, that wasn’t the case, and I’m hoping to get some practical advice on the state of this one battery that suffered through the idle time quite differently from the others.

Do you have any feedback on that critical part of my post?

[quote=“deinspanjer”]Yesterday, I pulled it out and checked the charge on them. The two older ones were at about 4.11V, and the cells still balanced within 0.1V of each other. The newer one had a higher state of charge, about 4.14, also balanced, but I noticed as soon as I pulled it out of the slot that it had swelled a bit.
[/quote]

While reviewing Andre’s reply, I realized that it might be possible that my original post was misinterpreted because of poor wording.

What I meant to say was that all of the batteries were still at an almost full state of charge after the 3 week hiatus. 4.11V per cell for a total of 16.4V on the old batteries and 4.14V per cell for a total of 16.56V on the new (and bulging) battery.

This means that the two old batteries drained about 0.2V each, and the new one drained only 0.04V. All figures approximate, but when I recharge the batteries, I typically do so at 1C and they recharge to about 16.6V.