At what current do protected batteries protection trip?


I have a light that has one of the IOS 3.5 amp (now, 4.5 amp) drivers, and I think that I’ve noticed that if I use protected batteries (e.g., 2x18650s protected) that when the switch is clicked, i just get a flash and then it turns off. This only happens with protected batteries, and it works fine with unprotected batteries.

With unprotected batteries, I’m measuring in the range of 3+ to 4+ amps tailcap currents, so I’m suspecting that the protection PCB in the protected batteries is tripping. Does anyone know if this’d be the case, and also at what current would the protection trip?

FInally, if this is the protection circuit tripping, does that mean that with drivers like the IOS 3.5/4.5 amp driver that only unprotected batteries can be used with them? I guess that’s kind of a question with an obvious answer, but wanted to confirm.


Not all protected cells are made the same. I tried to run 2 Eagletac 3100’s in my Direct Drive MT-G2 drop in. It shut off almost immediately. I put 2 AW 2600”s in it and it will run till I can’t hold it because of the heat.

AHH! One of the protected ones I had was an Eagletac also :(. When you say “shut off almost immediately”, was it like you clicked the switch, it flashed briefely, and then turned off? That’s what I was seeing!

I just put 2 Panasonic 2900 protected cells in a cold J18 (Its been outside for a few hrs). It flashes and then nothing. I tried a second time and again just a flash. Cycled to medium mode and it stayed on. Left it on for about a minute on med, cycled to high (saw that it worked) and turned it off. Waited for 30 sec and tried on high mode again. This time it worked fine without the circuit tripping.

So when my J18 is cold, it puts out higher current but only for a few seconds until things heat up….am I observing correctly? Does that mean then my J18 is poorly heatsinked?

There’s some discussion about that behavior here:

It sounds like what you’re seeing?

Yeah bro…the part about really high amps on 2 cells and that there might be some weird thermal issues going on. It hasn’t dimmed nor has it had switch issues but I really haven’t ran it longer than 30 sec at a time on high. Sorta afraid I guess…lol.

Before I got these pannys and some TF 26650’s, I was using some unprotected pannys and got up to 7 amps (14A) for a couple secs before nosediving down to 4A. All within 30 sec or so.

I wonder if its a driver issue or if the emitters are poorly attached or…? That thread was from dec 12 and there’s been no updates by Tom. I guess ill shoot him a pm. Thanks for the link. I haven’t seen that J18 thread.

Oh, and to stay on topic, yes my Panasonic 2900 protected cells trip at around 7A (or is that 14A?) in my J18 on 2 cells.

I always thought that it was the voltage drop during a heavy current draw that trips them. That is why cheap cells, or worn out cells trip earlier than good cells (high internal resistance)

Protection circuits can have nearly any imaginable combination of low voltage, high voltage, and overcurrent cutoffs in them, though the low & high voltage points can't vary by much just due to the cell's chemistry. Overcurrent can be anything from as low as 1 amp (I have some white TF 16340s that would trip at 1A) all the way up to, well, who knows. Whatever they decide to program them with.
The info you seek is near the bottom of the page, under Current.
Also if the batteries are of low quality or tired cells it possible the battery sag is just so low under the heavy load that the pcb is tripping from low voltage.

The info on that page about the current trip appears to jibe approx. with what I was seeing. One of the pairs was Eagletac 2100.

So 2C would be 4200, and 30% above that would put the approx. trip current at 5460 mA. When I measuring the tailcap with an IMR pair, I was seeing about 5.4 amps at the tailcap, which would be just about that.

Wassup fellows?

After peeking over the popular DW01-P datasheet I have lying around, its overcurrent detection voltage is specified as 150mV. It seems to me this voltage differential is monitored between the Current Sense pin (P-, after the FETs) and the Test/Ground pins (at battery cathode), so mathematically the tripping current should be:

Mmm, been tinkering for a while with an equation editor software for a while now, hope the stuff looks good.

Hope this serves as example of how protection ICs typically operate in this regard.

Cheers ^:)

Barkuti you wake up more Zombie threads than anyone else I know. It’s not a bad thing, I’m just curious how you come across all these older topics.

Well pilotdog68, maybe it has something to do with the fact that, when I have some sort of question, I usually use the search engine first and do some related term searches. I found this thread on the search result page 3 for “overcurrent”.

Cheers ^:)