NiMH will not hold charge!!

[Gaffle]

I have had some Energizer NiMH around for about 1.5 years now. I recieved a charger at the same time. It is a Energizer CHFVC(PDF). The charger always seemed funky to me. You must charge 2 batteries at a time and they must be the same type. Most of my lights use 3 AA/AAA (headlamps) so it is a pain to charge an odd number. The charger must be reset (unplugged/plugged back in) before you put in some batteries to charge.

A few months ago I charged 4AA for my ProPoly and the light did not seem to last as long as it did with alkaline. I just thought they sat in the light long enough to discharge, they are not LSD NiMH. Right around that same time I charged a set of 4AA so I could use 3 of them in my Myo Xp. The Xp has a battery indicator function. It has a small light that blinks green until the batteries are spent to 70%, then it goes to orange until the batteries are spent to 90%, which it then blinks red. I put in fresh NiMH and use the light for only 20 minutes, BOOM, it does the 70% discharge flash and the orange light starts flashing.

Well it is official that either the charger is a piece of crap, or the batteries will not take a charge anymore. I have not beat up the batteries before this has happened. Not like they have had 900 cycles or anything. I don't think I have done anything to wreck the batteries capacity.

A good NiMH charger recommendation would be appreciated.

Off my topic, but are those Ray-O-Vac chargers any good? I saw a charger+2AA+2AAA package for $10. It was a slow charger, not fast. The batteries were the Hybrids.

 

[VidPro]

its both
get some enloopey things and one of them wizz bang $60 chargers that tests the cells, your out 100$ for 2 years, thats cheaper than cable

if the wifey complains, i will write you up a prescription :wave:

you really do want at least some type of charger that has seperate channels for the cells, so each cell is treated right, the 'Ol charge them in seires worked back in the 1300's (ma) but higher capacity batteries are more pickey, specially if your using 3.

 

[SilverFox]

Hello Gaffle,

I don't like the fact that the charger only charges in pairs, but other than that, it seems like a reasonable timed charger.

With a 200 mA charge rate, and a 16.5 hour timer, you can do "standard" charges on 2000 mAh cells, and probably do a reasonable job of charging higher capacity cells, although you may have to unplug and plug back in to reset the timer for C and D cells.

A couple of questions...

Your battery indicator on your light may just look at voltage under load. As batteries age, their internal resistance increases. This results in lower voltage under load. The question involves the actual run time. If you are getting about the same run time, your batteries have simply aged. However, if your run time is below around 80% of what is was initially, you have "crap" cells.

The next question is how hot do the cells get while charging? Cells with higher internal resistance tend to heat up more than vibrant cells do.

In spite of the fact that your charger isn't totally "crap," I would still suggest finding one that does single cells. I happen to like the Maha 808M for AAA, AA, C, and D cells, but it doesn't do 9V.

Tom

 

[Gaffle]

Your battery indicator on your light may just look at voltage under load. As batteries age, their internal resistance increases. This results in lower voltage under load. The question involves the actual run time. If you are getting about the same run time, your batteries have simply aged. However, if your run time is below around 80% of what is was initially, you have "crap" cells.

I actually cannot remember if the light actually dimmed. I know that NiMH in the Myo Xp should not set off the indicator (at least I have not read about it). I do know that my ProPoly Lux dimmed very very fast on a fresh batch of NiMH. Faster than normal.

The next question is how hot do the cells get while charging? Cells with higher internal resistance tend to heat up more than vibrant cells do.

This I do not know the answer to this question. I will have to check sometime today. Does the heat peak at the end of the charge? Is this when I should see how hot the batteries are?

 

[SilverFox]

Hello Gaffle,

Yes. It may be beneficial to check the heat at 5 hours, 10 hours, 15 hours, and at the end of the charge.

Tom

 

[Avatar28]

I think those Energizer 2500 mAh cells have been having some serious longevitiy issues too haven't they? I had a set that at least one or two of the cells seem to have crapped out. They would not run very long at all and really didn't have all that many cycles on them, probably no more than 50 or so. I thought I killed them with a faster rate charger (and maybe I did), though I still haven't thrown them out because I wasn't sure exactly which ones were bad and they got mixed into my general population. I'm not even certain those are the bad cells, though I think they are. I have one of those Duracell power gauge chargers and on one or two of those it never would complete charging, it got hung up at two bars out of the three and stayed there long after the other cells were complete. If I took them out and put them right back in then the error light would come on after a moment but if I let them set for a bit I could then try charging them again and they seemed to complete the charge cycle successfully. That's far from the best charger in the world, though, so I don't know exactly what was going on, but at least it has independent channels.