Determining which batteries (of 4) are bad? (Nitecore TM16 now works!)

Months ago, I had a thread (http://www.candlepowerforums.com/vb/showthread.php?421774-Nitecore-TM16-won-t-work&highlight=) where I expressed dismay that my TM16 light would not work any more. Good news after a lot of anguish... it works! I bought a new set of 4 Nitecore NL183 18650 2300mAh batteries. It turned right on, so, I guess it's okay.

So, what about the four identical batteries. They came in the flashlight. I had it maybe a year. I don't know how much usage I had with it but I am not a heavy user. I did go on a few fishing trips where it got a lot of use. I don't know if I ever ran it all the way down but it got a few hours use on each trip. (Off and on while boating.)

Is there a way to tell which ones are bad? And if I do, say it is one bad one. Would the other three be usable if I bought one new one? Or do you have to have all four batteries of the same 'vintage?'

Happy my Tm16 works again.

Does the light hold the cells in series or parallel? And an analysing charger can determine the bad one

vicv said:

Does the light hold the cells in series or parallel? And an analysing charger can determine the bad one

Click to expand...

I forgot to say that the meter shows 4.14 - 4.17 v for these four 3.7v batteries.

Series or parallel? I don't know much, lol. I don't know what that means. Two have positive posts up, two down. What does that mean, lol. I am guessing -- serial, lol.

An analysing charger, I don't know. I have a DMiotech Smart-C charger. I darn sure don't know what to do with it, lol.

Pretty ignorant on all things electronic.

Ok two up and two down should mean they're in series. Or 2s/2p. Either way you should not buy a new cell and add it to the remaining 3 to use in this light. For an analyzing charger look for an iMax b6AC. They're ~$30 and can do everything you need. Also get a pack of small neobium magnets. If you don't want a hobby charger get an opus b3100 or miboxer c4. They have discharge function and will let you know which is the bad cell by either a lower capacity than the rest or the culprit will have much lower voltage when you start the discharge. For the remaining three good cells enjoy them in some other lights

To test the batteries I would:
- Charge them up
- Put them in the light and run it for a bit
- Pull the batteries and take a voltage reading on all four.
- The bad one is likely the one with less voltage.

Note: If you have a charger that can cycle the cells do a Charge/Discharge cycle and you should also be able to see which one is bad.

You should run batteries of the same vintage together. Don't put a new cell in with the four older ones. Just use the three good cells in other lights.