How do you know when to retire your batterys?

Either of these scenario:

1. They puff up like a popcorn bag after some physical damage or abuse (such as over-discharging or discharged at excessive rate)
2. when your internal resistance gets to high compared to when they were new (you will get really bad voltage sag at wide open throttle), and lipo battery gets really hot after a flight

Some of my 4S drops to 9.7V durig full throttle. not puffed yet, but it is probably time to get some new packs

(05-Mar-2017, 08:59 PM)Oscar Wrote: 1. They puff up like a popcorn bag after some physical damage or abuse (such as over-discharging or discharged at excessive rate)

Do you discard when there is any pufffing?  Or is there an acceptable amount?  (I've got some airplane buddies who recharge and fly puffed batteries all the time - I've always been timid about charging puffed batteries.)

(06-Mar-2017, 02:36 AM)sloscotty Wrote: Do you discard when there is any pufffing?  Or is there an acceptable amount?  (I've got some airplane buddies who recharge and fly puffed batteries all the time - I've always been timid about charging puffed batteries.)

I don't think puffy = explosion, puffier just means it's more likely to fail. I also find puffy lipo has a higher internal resistance. There is another post in this section explained why lipo puffs, and why putting them in freezer isn't a goo idea

I do use slightly puffy packs and I will probably replace them soon. It's just the amount of risk each person is willing to take

(06-Mar-2017, 10:33 AM)Oscar Wrote: I don't think puffy = explosion, puffier just means it's more likely to fail. I also find puffy lipo has a higher internal resistance. There is another post in this section explained why lipo puffs, and why putting them in freezer isn't a goo idea

I do use slightly puffy packs and I will probably replace them soon. It's just the amount of risk each person is willing to take

Hi Oscar,
..since there are several cells in a lipo, I found that the puffing doesn't touch all of the cells at once. I've been taking them apart, and some cells still look just fine. Do you have experience with "Frankenstein-ing" good used cells with identical specs together?
Two half-puffed 4S Lipos would give you one just fine intermediate one, and you could squeeze out the e-juice until the very end..

it can easily be done, I have done it a few times. Just have a very powerful iron as these batteries suck heat

Yes it's doable but quite risky IMO.. we actually have a tutorial on that if anyone's interested:
https://oscarliang.com/fix-lipos-bad-cell/