Rechargeable options for 16340 in multi cell applications

[Scottiver]

So I have a couple of lights that use two 16340 size cells and have been using AW IMR cells because those were recommended at the time as the best chemistry for multi cell applications. AW's are no longer made and not many other options out there these days for IMR. Can I just use two quality protected lithium ion batteries? ARE IMR's better for multi cell use? My SPY 007 has the batteries side by side so an 18650 or 17650 won't work. An hour on Google didn't get my any answers. Thanks for any insight... : )

 

[delus]

IMR is generally considered to be the safest chemistry. That doesn't mean they are 100% safe, just that they are widely considered to be a safer choice.

I use two AW IMR 18490 in an elzetta charlie that's been bored for rechargeables. I used to have six of them. Meaning, over the last five years, four of my 18490's have been over discharged to the point that the protection circuit tripped.

In my experience, here's what happens:
If I use the light on and off, on and off, to the point where they are low, the batts come out of the light in a fairly equal state of charge. Within .1 or .2 volt of each other.
If i use the light steady on until the batts get low, that's when the one towards the negative end will come out with a much lower charge than the other. Half a volt difference, or worse. Or worst. The negative-side battery is charging the positive-side battery. I suppose that's one of the reasons Elzetta recommends only primary batteries.

My LUC-V4 charger has a "Zero voltage activation function" and can bring batteries back after the protection circuit has tripped, and I tried that twice, and it seemed to work both times, but I don't like to play around with that kind of thing, so I tossed them anyway. How do i know the protection circuit wasn't damaged, and will work again next time?

The best thing to do is don't let them get low. 3.5 volts is low enough to recharge.

18490's are somewhat rare. Some "reputable dealers" had them in stock, but wanted ten bucks each. I found somebody on eBay that sold me four of IMREN brand for $19, free shipping. So far they seem OK.

Interestingly, when I first got the Elzetta Charlie, it's tube was not yet bored for 18xxx cells, and I tried using three 16340's. The third one in series (the batt on the negative end) came out dead every time. So, three is worse than two. The third one was charging both of the others.

I see several brands of IMR 16340 on eBay.... Fenix, Olight, among others.
And I see A123's for 1.10 each if you buy 50. That will solve all your problems. They are supposed to have extremely long shelf life.

 

[Scottiver]

Thanks. I did buy some Olights that were supposed to be IMR, but no where on the battery does it say IMR. It says RCR123A, which sounds to me like just standard rechargeable Li-ions.
But just wondering if anyone uses standard protected Li-ions two or more at a time?
Is this standard practice at all these days...

 

[delus]

It can't be all that bad. The worst that can happen is you toss a cell once in awhile.
I always imagined that in those 4-cell-in-series carriers it actually winds up being two-in series plus two-in-series. Is that correct? If it is four-in-series I bet we'd get tons of complaints.
As far as I know the Meteor M43 is the only four cell configuration that's in parallel.

I'd put a number on each of your new cells.
And these days a charger that shows exact cell voltage is a must-have for all serious flashaholics.
Last year I put a clipboard next to my charger and individually track each cell's starting voltage. So far I've learned that it's not worth it to salvage cells from my makita packs, I'm just not getting good performance from them.

 

[delus]

I just checked the two lights I have with the four-cell carriers, and I can see the circuitry on them are 2+2. It's not 4 cells in one series. I'm willing to bet they are all like that. So, yes, it is standard practice to run 2 rechargeable cells in series nowadays.
Let me say again that I had very bad results when running three rechargeable cells in series.