Possible Eneloop AA damage, questions inside

Hello all,

I use Eneloop AA's in a lot of my electronics, with the main two being flashlights and handheld ham radios. I have a replacement backer for my handheld radio that takes 6x AA batteries.

Like an idiot, I plugged the radio into the wall charger without confirming which cell was in it. I immediately unplugged it to remove the cell and check. I noticed at that time it was extremely hot and felt like it was getting hotter by the second.

I quickly yanked the Eneloops out of the case. The plastic on the case melted in some locations. The radio works fine with its factory battery pack.

My questions are:

1) In layman terms, can you tell me what happened?

2) Are these Eneloops still useful? I haven't tried to use or charge them since. I know batteries can be dangerous so I wanted to gather some information first.

Thanks for your time.

if radio is old tech, it only means adaptor and battery share the same input and most probably reverse overcharge the battery in the process. ( im expecting adaptor to at least have 9v output. nimh only has 7.2.

if you have smart charger , test capacity in a safe place. since there is still no records of eneloop poof, im sure that is still ok. but test it first just to be surely safe

Radio is old tech for sure. Yaesu FT-60R. Reliable but not cutting edge.

The thing that surprised me was it seemed like the heat (and what I assumed to be the "problem") was growing even after the power was removed. My thought was to pop all the cells out and hopefully stop the problem from growing and blowing up a battery in my hands. Not sure if that's logical or not, I'm not great with batteries and circuitry.

The only charger I have is the one that came with the Eneloop batteries.

TFin04 said:

Radio is old tech for sure. Yaesu FT-60R. Reliable but not cutting edge.

The thing that surprised me was it seemed like the heat (and what I assumed to be the "problem") was growing even after the power was removed. My thought was to pop all the cells out and hopefully stop the problem from growing and blowing up a battery in my hands. Not sure if that's logical or not, I'm not great with batteries and circuitry.

The only charger I have is the one that came with the Eneloop batteries.

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I can highly recommend the La Crosse BC-700 charger for your eneloop batteries. I have used this charger/tester/reconditioner for several years, and it has worked very well. The manual is not very good, but the charger is excellent. Each on the four compartments operates individually.

As to those batteries that were in the radio, I would recycle them-I would not want to take a chance.

Hello TFin04,

It could be that the charger just continues to trickle charge as long as it is plugged in. This is a quick way to ruin low self discharge batteries like Eneloop. The unit appears to be set up for NiCd batteries that can take this abuse somewhat in stride.

The heat is a result of over charging or charging at a high rate or missing the termination signal and continuing the charge past the point when the batteries are full. There is a chemical reaction taking place so when you stop the process there is a lag until the temperature begins to fall off.

While you may have done some damage to your batteries, they may still be able to offer some service life if you stop abusing them. The first indication of damage is a reduction in capacity. The next indication is a faster than normal self discharge rate. Keep an eye open for these changes. The best way to check for these changes is by using a charger that has analytical capabilities or a battery tester like the West Mountain CBA.

You may want to change the way you charge. If you keep using the charger that came with the device, you need to monitor the charge and keep on top of it. If the battery starts to heat up, stop the charge. Also don't leave the charger plugged in continually topping off the battery. The other approach is to throw away that charger and replace it with something that has some additional features and is designed to minimize the abuse to LSD batteries like Eneloop.

Tom

Maybe I wasn't clear. I wasn't trying to charge the Eneloops via the radio DC plug. I thought the factory NiCd battery pack was in.

I charge the Eneloops by removing them from the pack and using the factory Eneloop charger. The moment I inserted the radio charger with the Eneloop batteries in I noticed the heat issues.

I guess I'll try the batteries out and hope they aren't damaged. It was six of them in one shot, that's like 1/3 of my whole stash, ha!

Hello TFin04,

OK, that makes it a little clearer. Eneloop and other LSD type batteries don't do well with the NiCd charging algorithm because it will overcharge them causing heat.

You may want to consider tying a ribbon around the Eneloop battery pack. When you put it into the radio, remove it and tie it around the radio handle. This will serve as an alert to not charge it using the radio charger. Or use some other method to alert you that you are using the Eneloop pack.

The other concern I wanted to address is safety. NiMh batteries have a vent and usually they get hot and simply vent. There is a possibility that the vent can become plugged and if that happens you end up with rapid disassembly. With this you get a loud pop and sometimes you will have a projectile fly across the room. No flame occurs during this process. As you have experienced, hot batteries can melt plastic.

Tom

SilverFox said:

You may want to consider tying a ribbon around the Eneloop battery pack. When you put it into the radio, remove it and tie it around the radio handle. This will serve as an alert to not charge it using the radio charger. Or use some other method to alert you that you are using the Eneloop pack.

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Good idea. When I buy the replacement pack (this one is ruined) I will mark it with a paint pen.

The other concern I wanted to address is safety. NiMh batteries have a vent and usually they get hot and simply vent. There is a possibility that the vent can become plugged and if that happens you end up with rapid disassembly. With this you get a loud pop and sometimes you will have a projectile fly across the room. No flame occurs during this process. As you have experienced, hot batteries can melt plastic.

Tom

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Given the fact that the Eneloops cooled down immediately and did not leak, should I assume they are safe to use?

Hello TFin04,

This is one of those cases where you have to try it and see how well it still works. Eneloops are reasonably robust so there is a reasonable chance that you didn't do too much damage.

Another thing to keep in mind is that the term "hot" is relative. With batteries think of pulling a baked potato out of the oven. If you can't hold it but need to toss it from hand to hand, it is hot. If it is cooler than that it is simply "warm." Venting occurs a little while after "hot."

Tom