I like to get as much use out of my primaries as possible. When my alkaline aa’s won’t work in other devices anymore, I use a Sipik SK58 to use up whatever energy is left in them. The driver does a good job and usually takes them down to well below 1v. The result is a nice moonlight/firefly light output before it complete dies out.
I recently got into cr123 sized lights (after having avoided them for years) and acquired a couple drained primaries that didn’t work any longer in a friend’s steripen. I tested them in a Thrunite T20 to see how low they would go. Using the firefly mode I got two samples down to the 2.4-2.6v range. I thought they were pretty good and dead. Then I had the idea to try them in series with a high voltage P60 drop-in. They worked, but the light was relatively dim and only drew about 0.01 amps. Obviously there’s not much juice left in them.
So the question is, if lithium primaries are in a low energy state, is it dangerous to use them in series? I know the dangers of mismatching, but in this case they are pretty much matched because they are both more or less dead. Would ~0.2v make a difference? Does the risk and degree of violent explosion depend on the amount of charge/energy left?
BTW, for really draining batteries, I know about the joule thief, but haven’t the desire or ability to build one.
Yes, extremely dangerous. The problem is when say one is at 3 volts and the other is at 2.5 the one at 3 volts will keep supplying power and the one at 2.5 will quickly drop off and could reverse charge.
I tend to be pretty ballsy when it comes to batteries: I use unprotected 18650s in series, I try to reverse charge lithium primaries (AA version) but I hate CR123A batteries. I would much rather run 2 16340s than 2 CR123As, atleast the 16340s don't have as much of a tendency to explode.
Ballsy could be an understatement after reading the AA lithium thread… I can’t keep myself from experimenting a little too, but sometimes I stop myself because I’m scared of the results. Also I don’t have an ammo can, a thermistor, or mineral oil.
So what is the difference between lithium AA and cr123a besides dimensions? Is the chemistry different? What makes cr123’s that much more dangerous? Btw, I understand your example, but if both batteries are at 2.5v, does that still pose a risk?
If they're both at 2.5 volts then it is not as dangerous but the problem is if one was discharged at 3 amps and the other at 10 mah then a different amount of energy will left and the internal resistance will be different. Since the internal resistance is different inbetween the 2 of them then one will discharge faster and could still lead to reverse charging. (Not as likely but still possible) I would recommend sticking to just one battery though.
Oh yeah. The different voltage thing… I forgot about that. Thanks for the info links.
So the difference in internal resistance is why one cell in a multi-cell set up always ends up lower than the rest during deep discharge. So in my PIR light example with aaa eneloops, it’s probably the same cell that keeps going into negative voltage (at least I think it is, I should label it next time) which increases its internal resistance and makes it more susceptible to do the same thing in the future. Kind of a vicious cycle.
Theoretically, if all the batteries in series have the same exact internal resistance, this wouldn’t happen?
Even with the same internal resistance they could have different capacities to begin with. The difference in that amount is probably less than the variance in available power caused by different internal resistances. You did ask theoretically though.
I have had a few CR123A which measured 3volts, but they wouldn’t deliver anything. Amperage sagged to 0.1A under load, immediately.
Those had been brand-new Panasonic cells, even. Fresh out of the box, measured full voltage, but lacked the amps to back it up.
Ever since, I do NOT use more than one at a time. Running those CR123A in series poses a risk I certainly don’t want to take. In a one-cell light, like a SolarForce L2m, T4 or quarksevenwhatnot1x123, there’d be no problem. but in a multi-cell light…. thanks, but no thanks!
Hi.
I’ve recently started using flashlights that use 1xcr123a (T21, MT1C, sens cr). I love and only use Duracell batteries or nitecore.
Can I be without fear, because they are not multi-cell?. I appreciate more opinion of those who hates CR123A (From other people also appreciate the opinion).
Thanks.
Quote from lakeotter……“]I like to get as much use out of my primaries as possible. When my alkaline aa’s won’t work in other devices anymore, I use a Sipik SK58 to use up whatever energy is left in them. The driver does a good job and usually takes them down to well below 1v.”
This is one sure way to get a massive leak out of alkalines. Ask me how I know.
