Lipo safe charging bag

[ILLusion]

Hmm... I'm still oldschool... back when even charging a 2400mAh Nicad pack at 2.5C was considered ludicrous. LOL

Why would his pack be developing heat, then?

[krap101]

Originally Posted by ILLusion

Hmm... I'm still oldschool... back when even charging a 2400mAh Nicad pack at 2.5C was considered ludicrous. LOL

Why would his pack be developing heat, then?

Don't all batteries produce heat when being charged/discharged? It might have just been more noticeable with the bag?

[Kos-Mos]

a normal pack will hover around 40degC when fully charged.

That means you can hold it bare handed no problem. If you can't, it's too hot.

While charging, if the pack just heats and no swelling occurs, it's a cheap pack or you simply charge it too fast. Not all packs can take above 2C...
It might have to do with the quality of the charger too. The charging method for LiPo only forces the set current for the first 30% or so of the charge. Only until the pack reaches the trigger voltage. Then voltage is locked and current is simply drawn by the pack as needed. A full pack should drain under 10mA. That is when the charger detects the end-of-charge condition.

If it swells, it's dead, dispose of it.

[Sequential]

Originally Posted by ILLusion

Hmm... I'm still oldschool... back when even charging a 2400mAh Nicad pack at 2.5C was considered ludicrous. LOL

Why would his pack be developing heat, then?

Your not the only one old school. Never can be too safe, I'd rather nicely overnight charge my batteries than to shorten their life by doing quick charges.

[Freeze]

Originally Posted by ILLusion

5C? Wow... No wonder you're having overheating issues. 5C on a 5000mAh pack is equivalent to a 25Amp charge rate! Even thinking about charging a NiCad pack at that rate is absolutely insane, and NiCad packs are fairly robust!

You're definitely charging WAY too high. Even a high quality pack shouldn't be charged at more than 2C or 3C AT MOST, and even most experienced RC hobbyists don't recommend more than 1C unless you're using a very high quality balancing charger with proper ventilation on the pack.

No wonder you're having heat problems. Again, it's not the pack - it's your charge rate. Be glad the battery hasn't blown up yet, or worse, burned your house down to the ground or blown up beside your face while shooting your gun! One thing's for certain, the lifespan of your packs are most likely damaged. Check for swelling or bulging of the packs and toss them if they're swollen. They're now a safety hazard.

I forgot to mention that these are "Hi-Performance" LiPos for other applications. Like R/Cing. Because R/Cing is fun and I think the draw from a brushless motor is pretty high.

I will, however, start charging at lower current. Hopefully they won't heat the heck up like that anymore...

[ILLusion]

Let me know how that goes. I'm curious to know why your packs are heating up as well.

[Freeze]

Ok, they don't heat up as much now when I charge them in the LiPo sack, but they still heat up nonetheless.

While charging at 2C.

It doesn't swell, all the connection seem good, wires aren't melted (I'm checking problems that happened to my airsoft gun -.-).
It also runs just fine for 40-50 minutes continuously on a 3500kv brushless motor.
I'm starting to suspect my charger.

[coach]

Is it warm to the touch or is it hot?

Try rolling that back to 1C (5 amps for your 5000 mAh) and see what happens. Your hi-performance batteries might have a defect or aren't all that they claim!

[ILLusion]

Like coachster said... try taking the charge rate down further.

Heat is a wasted energy by-product when you charge beyond a pack's chemistry is able to intake.

[MadMax]

There really isn't much reason to exceed 1C with Lipo in airsoft applications. If you have a big battery, you shouldn't need a recharge for the rest of the day. RC models with high duty cycles aren't very much like airsoft. Getting several flights a day is facilitated by pushing 2C charging rates, but you're going to lose on battery cycle life pretty fast if you let it get too hot to touch. Lower threshold of pain is about 50C (120F). Lipos start to take thermal damage at around 60C (140F) where they start to roll into thermal runaway. Throw that battery into a bomb bag and you'll reduce it's ability to shed heat.

1C means about 1hr. Is that really too long? If you care about your expensive Lipos, charge them gracefully at around 0.7C (or lower) the night before a game. Shoot to your hearts content on gameday, then put them in a ziplock bag and toss them in the freezer. Industry storage practice for long term Lipo storage is to store them in sub zero temps at 30% charge. Lipos kept at full charge capacity suffer higher capacity degradation. Letting them drop below voltage due to self discharge does the same.