Duraloop up and died...

[lonesouth]

I was running two Duraloops in a Fenix LD20. It started acting funny, i.e. wouldn't turn on after being on for a short time, less than a minute. It was almost acting like my LD10 did when it had a bad tail switch. After a few clicky no light cycles, I checked the batteries on my el cheapo thomasdistributing free battery tester. One rocketed over to good, the other just sat there, not moving at all. I'll put a meter on it when I get home, but I am thinking it will read 0 volts and open. I also tried to charge it in my Accumanager20, but not even a light. I'll put my meter on it when I get home, but I am thinking it will show 0 volts and open.

Any thoughts on why it died?

 

[lonesouth]

ok, it happened again, different batteries, same flashlight. One died, the other is still working. I checked the voltage on the cells, the good one read around 1.2v, then bad 0.0. For kicks, I checked the resistance, understanding that it usually will not tell you much, and the good cell was open, but the bad read about 14ohms. What is interesting about the first bad cell is that it is now working...The incident tonight ocurred after a taking my LD20 on a jog, on strobe the whole time, in about 95* Florida heat...

 

[Marduke]

Are you matching pairs?

 

[lonesouth]

I am now...got out my label maker tonight and numbered em, created a spreadsheet...but lets not let the wife find out, she already thinks I am a nerd!

 

[mdocod]

Interesting...

You are certain that your duraloops are true re-badged eneloops and not the other "version" that floats out there?

I haven't had a single eneloop fail me, regardless of what level of abuse I try.

 

[VidPro]

in a series set with a "boost" driver one of the batteries will get depleated, that light item is very likly to be a boost driver without a 2V cutoff to keep that from happening.
sooo
one of the questions i would have is not that one cell was depleated completly, but how MUCH ofFset was the final capacity of the cell that still looked like it had something left?
and of course were they both fully charged. and in situations like THIS i would go so far to ask if your using a single channel charger or one of them duel battery series chargers. meaning do you know both cells were nicely topped off.
that is what i would wanna know.
basically you have an item here that can still depleate one of the cells fully, so after you analise your capacity possibilities, then you just dont run them down so far, or charge more often or something.
meaning if the "other" cell was almost gone,and you ran it all the way down, then thats about how it would happen?

you didnt indicate How Much RUNTIME you got prior to the occurance (or i didnt read it yet) unless your saying you got a few MINUTES?

as the capacity of one cell is fully gone, the voltage on the other could still be 1.1v (about) the high reading cell could still be basically empty.

 

[lonesouth]

i've been using an Accumanager20 to charge them. I'll have to do some searching to see how to test capacity with basic test equipment, then get back on that. I'm not certain about the runtime prior to failure as this light lives on my nightstand and gets used here and there for up to an hour at different levels.

 

[Mr Happy]

I think what happened is that you completely discharged your cells. A quite ordinary circumstance. You need to remove the cells and recharge them sooner, is all.

Some lights, like the LD10, do not have a low battery cut-off. They are like vampires; they will suck all the life force out of the batteries if you let them.

You mentioned above that one cell measured 1.2 V. This actually means it is completely discharged. For an NiMH, 1.2 V is empty.

When you try to discharge a cell below 1.2 V, the voltage curve becomes very steep and it will plummet down to zero with just a little more energy drawn from it. It is best not to do this as it will damage the cell.

If two cells are used in series, it is inevitable that they will not be exactly balanced in capacity. Therefore one of them will plummet to zero before the other does. Once that has happened, the light will start to have trouble sucking enough energy out of the other cell to keep working and then it will finally switch off.

What you need to do is not run the light until this happens. Remove the batteries sooner and recharge them before the voltage of either gets down to 1.2 V.

 

[lonesouth]

MR Happy I think hit the nail on the head. I checked the 'vbad' battery tonight and it did read 1.16v. My charger is now happily blinking away. I placed the two batteries charged last nihgt in the LD20, both measured ~1.38. Thanks for the advice, guess I'll just get in the habit of recharging them once a month or every other week depending on use.