View Full Version : OT: Goofy NiMH batteries

J Tiers
01-16-2016, 03:19 PM
I've never had much trouble with these, they just seem to work.

But I ran across a couple AAA size, 750 mA hour that I have had around for a while, and they are strange. They charge up OK, and reach 1.62 volts.

But if loaded in a pocket Maglite (which I have had others in with success), they briefly light the light very dimly and die. However, after that they STILL measure 1.61V, and test good on a 75 mA load in a good battery checker. They just won't run the flashlight.

Mostly the NiMH is for a higher drain device, and I have used similar cells in the same flashlight. I can understand the concept of a dead cell, but not one that has somehow developed a high resistance but still has the capacity. It's a new one on me.

01-16-2016, 03:51 PM
They're 'surface charging'- they charge enough to fool a smart charger and/or have enough internal resistance to buck a dumb charger. RC car guys used to run into this
all the time and the cure (on bigger cells) is to charge at a higher rate. On a AAA cell, i'd just replace it.

J Tiers
01-16-2016, 08:01 PM
That "surface charge" sounds good, but how does it manage to die under flashlight load, and then be resurrected with good voltage and load capability (except for the flashlight) ?

I figured it was some sort of partial charge, but the death/resurrection deal is pretty odd.

The otehr set will not light the light at all, but have good voltage

01-16-2016, 08:06 PM
Something there is tricking you-

01-16-2016, 09:52 PM
They are made to be charged with Chinese electricity!

J Tiers
01-16-2016, 10:08 PM
They are made to be charged with Chinese electricity!

Of course... I should use 220V AC....... :confused:

I admit I have been tempted, but......

01-16-2016, 10:15 PM
You could try shocking them with a higher voltage for a couple seconds, I've found that sometimes that will break the memory of the battery.


J Tiers
01-16-2016, 10:54 PM
NiMH are touted as not HAVING any memory effect.......

I have several other devices using NiMH batteries, and they give no trouble. But then they also have dedicated chargers.

01-16-2016, 11:43 PM
No memory effect, but they do age regardless of the usage pattern. I don't recall the aging mechanism, but I've read that after about three years they begin to 'lose it'. Friend used his nimh powered drill for about six years before it became useless. I've had nicads last 10 years or more, and I had a set of alkaline rechargeables back in the early 70's that went for the full pull.

I have some nimh AAs that give trouble, and some that went 4 or 5 years without problems.

J Tiers
01-17-2016, 12:09 AM
One of the cameras has been using the same set of NiMH AA batteries since 2004. It still seems to last as long between charges as ever.

These AAA ones were not used for high drain, they were actually in remotes for electronics. Used a fair bit, but not a lot of power draw. With the experience on that camera, I am surprised these quit faster. The camera is a higher drain, but gets used considerably less, it sits for most of its existence, since I don't take pics every day with it.

Others in flashlights, and other things I don't even recall, have not been an issue either

Alkaline..... just recently had the last of the "renewal" alkaline batteries finally quit. They went a long time, but are no longer available.