Well Ivan, I didn't know that either, but I had a battery last summer almost brand new puffed on me, it was hot as hell that day, so it coulda been just a crappy battery, or it was hot and over heated the pack. I didn't run it too long or too hard, ran it about 4 mins and the pack had like 3.95 per cell on it, but it puffed up pretty good on me. I just don't bother now when its so hot out. I'd do like you and fly early morning, but I am a night owl, and cannot get my rear outta bed in the morning early enough to pack up and head to the field.