I recently grabbed my C3 centurion with three primary CR123As in it, and noticed it was dimmer than normal. I just worked on, I had to repair that amp quickly...
Only minutes later, I had to use it again, and.... it had its FULL brightness again. I didn't pay much attention to this, I thought some dirt must have been between the switch, causing a bad contact. I used it a few more times that day, no problems.
Until yesterday. I took it again, tested it and.... not even half of the normal light!
I hadn't used it in between, and NOW suddenly the batteries were dead?? I investigated, and only one of the batteries was dead. Still, all had 2.92 tot 2.96 Volts unloaded, but one was not even able to power up a Fenix P1D properly.... for quick testing purposes, I threw in one other CR123A in my C3, and it had full brightness again.
The faulty battery was a little warm, and continued to be so for more than an hour. I didn't trust it at all, so I decided to lay it outside, on a piece of concrete....
just took it inside, it has cooled down and nothing happened.
A defective CR123A cell it seems. Luckily it didn't vent-with-flames! The other two still good cells were reverse-charging the bad one. Note that defective/old batteries can appear x voltage on a multimeter, but as soon as subjected to a load, the voltage will drop way less then x.
I'd dispose of that cell!
I know there WILL be problems if I go on using the two still working cells with another, with an unknown status. I WON'T DO THIS.
As soon as I noticed the problems of suddenly not working as normal, I switched off the C3 immediately. And still, that few seconds have already resulted in a cell-warmup....
The two still working ones will be used up in my P1D and L1 LumaMax.
The next few days, four protected 17500s will come in. So no more problems like this anymore....
I will discard of this suspicious cell today! Before any burns, flames or other dangerous things happen
Most people would recommend sticking to major brands such as Energizer, Duracell and Panasonic batteries. Or Surefire cells, if you can get those locally. Another known good brand is BatteryStation, and I haven't read anything bad about Titanium Innovations, I have about a dozen of em. (From BatteryJunction).