Charging alkalines in NIMH Charger

The other day I accidentally re-charged AA alkaline batteries in my Titanium Pow-Power TG-700 Smart Charger, which is for NiMH and NiCad batteries only. They were regular Rayovac alkalines and I thought they were NiMH batteries at the time. Anyway, they charged up normally and are functioning just fine in my flashlight (Streamlight 4AA Luxion).

My question is what is wrong with charging alkalines in my charger on a regular basis? Is there a danger of them exploding or damaging the charger?

Thanks!

Greg

You got lucky, more importantly that charger isn't very "smart" if it didn't detect a non-rechargable battery and tried charging it. Alkalines usually don't explode or catch fire, but they will get very hot and may leak if the charger tries to force a recharge.

A guy at work told me it is possible to recharge alkalines slowly if they have only been discharged a slight amount.

I didn't think it was possible but apparently he and other guys there have done it before. Not very practical I guess, but kind of surprising.

Probably not worth the risk though! If they pop, they'll make a mess. I've seen it before a long time ago when some alkalines were left in a charger. There was a soft popping noise then hissing sounds.... "Hmm, what's that noise??"

Years ago there was a charger designed to recharge alkalines.It did this by charging at a very slow rate.It wasn't on the market long;too many batteries were going !!!

I accidently put a couple rechargeable alkalines in a NMH charger once. I don't think that they were in more than a couple hours. Heard a loud pop. 30 seconds later I heard another loud pop. I had several chargers going at the same time in several different places. Took me about a minute to find out where the bangs came from. Both batteries split open and leaked. Fortunately when it leaked it only dribbled a little and didn't spray it out of the charger. The charger was a direct plug into the wall type, so it was vertical and could have sprayed my carpet and a bookcase. If the batteries had dribbled more it would have hit the carpet anyway.

Alkalines don't take too well to being recharged anyway. The best way to do it is to charge little and often, else you're talking about 3 charges to 50% capacity. If you want to recharge your batteries, use rechargeables......

Despite this working, i recommend that you don't continue trying this. One of the ingredients in alkaline batteries is potassium hydroxide. Potassium hydroxide is a caustic agent that will irritate can can cause damage to your body if inhaled, or if you get it on your skin or eyes. If you standing near it when it pops the chance of getting it in you eyes is pretty good. While the concentration is only 20%, contact would not be pleasant, and could be severely damaging if repeated.

Just my 2 cents

Happy Holidays,
Chewy

Thanks everyone. I guess I was lucky to get away without a "pop" and a messed up charger!

- Greg

Not a good idea to do this. Also, you posted in the wrong forum. I'm moving it to the Batteries section.

Count yourself lucky. There are chargers that can recharge non rechargeables like the Rezap and the brand new Rezap Pro.

I put an alkaline AA in my rayovac 1hr charger and even though it blinks like an error the testing pulse will slowly charge the alkalines up but even though you can get alkalines back to 1.5v by *charging* them I think the capacity is already been reduced and the chance for leakage increases so much you are just asking for them to leak

DM51 said:

....Also, you posted in the wrong forum. I'm moving it to the Batteries section.

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Wait... someone posted a battery question is the wrong forum... and DM51 moved it? This is so weird.............................

LOL. I have to move quite a number every day - more than you would notice, too, as quite often I just move them without posting or leaving a redirect.

I do wish some people would give a bit of thought to where their new threads should be posted - they would get better and quicker responses if they did that, and it would not occupy so much moderator time either...

chew socks said:

One of the ingredients in alkaline batteries is potassium hydroxide. Potassium hydroxide is a caustic agent that will irritate can can cause damage to your body if inhaled, or if you get it on your skin or eyes. [...] While the concentration is only 20%, contact would not be pleasant, and could be severely damaging if repeated.

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A 20% potassium hydroxide mixture is nothing to sneeze at. An aqueous solution with 0.05% of this stuff has a pH of 12 and is perfectly capable of severly damaging your eyes.
So be careful with the stuff if it drips around. Lot's of water is usually the best remedy.

People have tested this and found it works to a certain degree. No need for fancy reverse pulses either, just a straight dc current with a 2V cutoff. Most batteries would recover 70-80% of their previous capacity, and after a number of recharges (10-20) they would become useless. Some brands were better suited to this than others, and a few would leak. Not sure where I found this info though.
My personal experience is that Duracells in particular would take very badly to recharging and would most likely leak (or even burst), but others would perform quite well actually. But my experiments were 30 years ago and battery chemistry may have changed since then of course. Use caution.
Wasn't there made a particular brand of alkalines (once upon a time) that were advertised to be rechargeable up to 15 times?

Resqueline said:

Wasn't there made a particular brand of alkalines (once upon a time) that were advertised to be rechargeable up to 15 times?

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There was RAM... or rechargable alkaline manganese I think? I had some rechargable alkalines and they were good for perhaps 20-25 charges till the dropping capacity made them useless. Batteries used to have metals cans in the AA/AA cells and now it is like foil paper in them I would be wary of trying to recharge them at all for the chance of leakage. Most people discharge alkalines too far to recharge them much anyway. I once had a tv set that the remote used a flat 6v alkaline battery that cost $7 each. It would eat one every 6 months so I ended up one day recharging it via a power supply by limiting the current to about 50ma or so till it reached about 6.5v. This worked about 5-6 times but after that I found it would only last a few weeks and finally got an ingenius idea of soldering 3AAAs together and using them instead as it cost me less than $2 for them and it ran for about 5 months instead of 6.

ANDREAS FERRARI said:

Years ago there was a charger designed to recharge alkalines.It did this by charging at a very slow rate.It wasn't on the market long;too many batteries were going !!!

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I remember such chargers being offered through Tandy down here in Oz, they even had a facility for button cells IIRC, personally I had decent success using (a low charging rate) NI-CD recharger though I only ever recharged the Alkaline cells ONCE (things were tight for a teenager during the 80's) :thumbsup:

FWIW my Grandcell dual charger puts about 3.4v @ 0.04~0.1A into it's RAM cells well below the NiMH recharge current (but with a higher voltage)

Yeah, when I was a kid, Radio Trash sold a charger (IIRC a NiCd one) that was advertised to also recharge ANY alky batt. OK: it worked, sort of. It would work only a few times (say, half a dozen on a good day during a leap year), and the capacity of the 'recharged' alky was only a tiny fraction of its original runtime. Still, for a few pennies of juice overnight, you got a little more runtime out of batts that otherwise would have gone into the trash. I do not remember leakage as problem; course, I could be suffering from a senior moment, so would not swear to this.