What a great day to fly rc airplanes. 70 degrees and not a cloud in the sky. Couple of my good flying buddies were out with me. I got two airplanes out. My 65" OMP Yak Profile and my 40% Aero-Works Yak. The OMP Yak was not charged and I decided to put it on the ramp of my trailer to quick charge on my MKIII Dual Charger. I set it where I normally set it and let it go.
As it was charging I had the Aero-Works Yak out and was going to mess with my Ailerons since I have been having problems with the ailerons lately. My friend was helping me out and just out of no where a bomb went off. Literally that is what it sounded like and I look to my left and saw a big smoke cloud go above my trailer. I was like ooo sh%%I thought a lipo battery I had in the trailer just randomly explode but I look and saw that half the wing in the omp was blown apart.

It was a 6 volt battery and omg what a mess it left. I am not lieing but one of the cells literally blew apart from the pack and went through every rib of the wing and shot out the wing tip and went another 50 feet away from the plane. Talking about some power out of that explosion. Luckily the way it exploded my FASST rx didnt get damaged as it was sitting underneath it. But everything was wrap. The wing can be repared but would have to rip all the covering off due to what that one cell going flying out. Here are some ok pics of it. I find it kind of funny now. lol

I didnt know these batteries explode like this.

Yes they do. Had the same thing happen in my 4wD off road buggy while I was driving it. Everyone thought I slammed into a brick wall at the end of the straight away. The battery peeled back and looked like they do in cartoons. Sounded just like a shotgun.

Fast charging batteries is never good for them. Eventually they will fail.

Originally Posted by sweetpea

Yes they do. Had the same thing happen in my 4wD off road buggy while I was driving it. Everyone thought I slammed into a brick wall at the end of the straight away. The battery peeled back and looked like they do in cartoons. Sounded just like a shotgun.

Fast charging batteries is never good for them. Eventually they will fail.

There was nothing left of this one. The shells were completly empty. It was like they were shotgun shells and look used. I just hope it isnt the charger. I have heard this charger over heating batteries a lot.

That is what causes it. On mine the batts get hot because we charged them at 6amps.

Then you run them in a car that drains them in less than 5mins. The batteries were always hot and typically only lasted a season before the "punch" was gone. These I had used for 2 yrs as practice packs.

What rate were you using? I never quick charge my batteries but I do charge at about 400mah on my rx packs, they are all 1500 to 2000 mah NiMh packs.

Tom

Originally Posted by blackbeer

What rate were you using? I never quick charge my batteries but I do charge at about 400mah on my rx packs, they are all 1500 to 2000 mah NiMh packs.

Tom

It was .8 to .9 amps.

Originally Posted by sweetpea

That is what causes it. On mine the batts get hot because we charged them at 6amps.

Then you run them in a car that drains them in less than 5mins. The batteries were always hot and typically only lasted a season before the "punch" was gone. These I had used for 2 yrs as practice packs.

Its so weird cause one of my friends never does the over night charge. He always used the charger I have and always quick charged his batteries with no problems. Only time I usually quick charge is either a day I didnt know I was going to field and I just hop in and go or if I fly the crap out of the plane and have to charge it.

I always charge my NiMhs on the day I'm flying just because they tend to loose more of their charge then NiCds and it doesn't take long to stuff 5 or 6 hundred mah into them before I go. My guess is that the charger is at fault. You should be able to charge at 1C with no problem. Bumber though, that was a great flying plane. I never trust a charger, even my Bantam though it has never let me down.

Tom

Originally Posted by Sukhoikid

It was .8 to .9 amps.

Dang, I kinda hope it was the charger. Or better a bad battery pack. I routinely charge my 1700Mah and 2000Mah NIMH batts at 1 to 1.2 amps. They never even get warm. In fact I wondered if I could up it to 2 amps and be OK.

Don't ever fast charge NiMH.

The AAA size NiMh cells are the fragile ones. I vented a 2000mah tx pack with only a 300mah charge rate. I switched to a 1650 for my tx but I still only charge it at 120mah. But their good for about 6 hours in the tx so it's no big deal.

Tom

The Wing can be fixed but called omp and they had one spare wing left. Just happen it was the left wing! I am lucky

Was this a commercially produced pack, or homemade?

Had one melt its way thrue my wing on A combat plane. Not sure why??

This is a good reminder that even NiMHs can start a fire. A couple of things to keep in mind. Lots of people are using the higher capacity NiMH cells. The way they do this is to use thinner material inside. This makes the cell far less robust than say a Sub-C cell is. They are less tolerant of overcharging, fast charging, and vibration.

Under no circumstances should a NiMH ever be charged at greater than 1C (I'm talking about RX/TX packs) and if you can charge a bit slower, that is better. I typically charge at C/2 (1/2 the rated capacity). I also will cycle the packs down and slow charge at C/10 every once in a while. This will rebalance the cells.

Cells typically let go because they have gotten way out of balance during repeated uses. An occasional discharge and slow charge can help with this.

Fire is a great thing, but not from your battery pack!!