2
$\begingroup$

I have some Ni-Mh rechargeable batteries (size AA/Mignon 1.2V, 2100 mAh) and just started to charge them using an automatic charger with 450 mA output.

Now one of those batteries surprisingly started to make silent fizzy sounds, like if you're frying something in a pan. It started within seconds after putting it in the charger and keeps going for minutes after removing it from the charger again. There is nothing visible from the outside though, I don't see any bubbles or leaking fluids.

  1. What exactly is the chemical process here that causes this sound (probably something is producing gas) and why does it happen in this one battery and not in the others I have of the same type?
  2. Is that battery still usable (safely?) or do I need to replace it?

Update: As of now, the battery in question is replaced and returned to a recycling station. I'm still interested in the chemical process behind this noise though.

$\endgroup$
  • $\begingroup$ sounds unsafe. discharge and dispose of it $\endgroup$ – Karl Dec 10 '16 at 7:44
1
$\begingroup$

I've heard of this before in lead acid batteries... it's caused by hydrogen gas being produced and leaking out of the casing of the battery.This is dangerous!!! It makes the very air in the vicinity of the battery explosive. Please dispose of ASAP!!!

$\endgroup$
  • $\begingroup$ We're talking about a Ni-Mh cell here though, not a lead-acid battery. $\endgroup$ – Byte Commander Dec 11 '16 at 14:07
  • $\begingroup$ That doesn't matter. Even though everything from Ni-MH to potassium hydroxide is used in batteries, the underlying principle of energy storage is the same in all commonly used batteries. $\endgroup$ – Harlemme Dec 11 '16 at 15:59
1
$\begingroup$

It's not possible to give a proper answer to (a) without examining the battery but it is likely due to a compromised casing. The noise is likely hydrogen gas leaking out as it's produced. Nickel metal hydride (NiMH) batteries use a metal hydride (MH) for energy storage. When this Hydride is exposed to moisture in air it reacts to form hydrogen gas: $$\ce{MH_x + xH2O \rightarrow M(OH)_x + x H2 }$$

For (b) I would say that your battery is probably not usable—safely or otherwise—anymore and may present a fire hazard. You should replace the battery as rechargeables don't cost near as much as the device they can leak inside of and destroy or the cost of fire damage to a house.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.