AAA NiMH will not charge

rhome said:

Last year I purchased several 4 packs of AAA NiMH batteries on sale.
These were stored properly in the original package,
Got them out today and tried to charge them in a new AA AAA wall plug in unit, the charger defaulted on all of them and would not charge the AAAs.
The charger works fine because I just charged some new NiMH AAs with no problems...also the mA of the AAAs are compatible with the charger.
Why are these unused 1 year old NiMH AAAs not taking a charge?
Thanks for your help.

Click to expand...

I am not an EE, bit if none of those 4 packs of AAA are charging, then it is the charger or user error (sorry had to put that in there). But more than likley it is the charger design or default. Get a different brand/model charger and see if that works, preferably the same company as the batts.

If they are different brands, check the + "tip" of the batteries compared to the ones that charge ok.
If there is a metal ridge or plastic around it it may not seat properly and fail to make contact in some chargers.
Inspect the opposite - end as well.
If they are the same brand as the charger I would email the battery company and ask for replacements.

I have been happy with the Maha C204W charger.
http://www.newworldvideodirect.com/productdetail.asp?productid=3116&refid=froogle
It has a mode that fully discharges before fully recharging.

I've found NiMH/NiCd cells die after a couple of years if not kept charged regularly, although just a year does seem very quick. Were they a cheap/no-name brand, or possibly had already been sitting around for a long time?

Do they have a manufacturing date on them?

I only buy low-self-discharge NiMH cells now, like eneloops. I've wasted too much money on cheaper ones which have died early. Plus, the eneloops keep their charge much, much longer.

Some nimh batteries decay in voltage in a very short time. If the voltage drops too low eg below .5 volt, the battery charger (some) cannot sense this low voltage to start the charge or pulse charge process.
This has happened to some of mine, they way around it, and it is dangerous is to use a 12 volt battery and just tap ths nimh battery for a millsecond. once usually does it, you may see a bit of a spark and the nimh battery will get a bit warm, but it will increase the residual voltage to a point that the charger will sense it and start charging.
I have used this method in the bush to fully charge a nimh battery from a vehicle battery.
nimh battey -ve to 12 volt battery -ve and, nimh battery +ve to 12 volt battery +ve.

Again it is dangerous, the nimh battery can get quite warm to hot and, possibly leak or explode.

I would suggest wiring a power resistor (or at least a few light bulbs in series) if you want to charge a NiMH like this - it's still risky unless you calculate the resistance properly to limit the charging current. I'm talking about charging, not the high-current zap to clear internal shorts and pull it's PD up. Maybe just one bulb in series for that... or not.

Please, please don't anyone try this with lithium-ion cells though - they can go off like flares!

Well folks I appreciate the quick and smart replies.
The -/+ of the batteries are clean....so just for sh#ts and giggles I'm going to try Thedragons millisecond quick zap method.
I've got goggles/gloves and all the happy safety crap to revive these little POSs.
Not a big loss, but I want to know how to prevent this waste for storing any more NiMHs.
Ain't technology dandy? It's much easier to maintain my old Deitz Kero lamps with extra wicks and 10 gal of K1 kero for backup lights.

foxyrick said:

Please, please don't anyone try this with lithium-ion cells though - they can go off like flares!

Click to expand...

Now how would you know this??

Captned said:

Now how would you know this??

Click to expand...

Li-ions are not safe chemistry. If you do use them they should have built in discharge protection, and a quality li-ion specific charger to go with them.

Eneloops are the way to go for ni-mh in AAA and AA devices. The newer ones hold 85% of their charge for well over a year and can be recharged 'up to' 1500 times.

I have them in all my AA devices and they perform as well as L91 lithiums except you can charge them up once they go flat. You can also push them pretty hard in high drain devices.

I've been using rechargable AA and AAA batteries since 1987. Never had one that could recharge more than 100 times. They still save money though.

Jash said:

Li-ions are not safe chemistry. If you do use them they should have built in discharge protection, and a quality li-ion specific charger to go with them.

Eneloops are the way to go for ni-mh in AAA and AA devices. The newer ones hold 85% of their charge for well over a year and can be recharged 'up to' 1500 times.

I have them in all my AA devices and they perform as well as L91 lithiums except you can charge them up once they go flat. You can also push them pretty hard in high drain devices.

Click to expand...

+1 on Eneloops. Worth the extra cost if you need reliability.