Panasonic NCR18650A

I have asked this in another thread but got no answer. No problem there, but I think it's a good question.

Why, if these batteries can go down to 2.3v and are able to discharge at really high currents, do we need a protection circuit? Surely in most lights it is fairly redundant? Or am I missing something?

I can understand most cells need to stay above 3v, which may be a problem in a light that takes 2 cells. As it could go down to 5v before the light turns off. Thus causing problems for the cells. But if these can go this low without damage, is a PCB needed?


I don't know that a PCB is ever "needed" however I would rather have it than not, just an added layer of safety in the use of these cells even though they are starting to get even safer before a PCB.

It is 2.5 volt, not 2.3 volt.

Because lights with 2 batteries in series or a boost converter can easily drain them below 2.5 volt

The problem for me is that my Jetbeam BC40 doesn't seem to like long batteries and they certainly won't fit in my charger. The other problem is they cost more, not a lot, but more.

I know most batteries would benefit from a PCB but these new Panasonics act as if they don't need one.


I have no problem with 2 EagleTac 3100mAh batteries in my BC40, they are protected, never given me an issue.

You know that protected batteries does exist in many lengths, also the NCR18650A.

I just tried two intl-outdoor 3100mAh protected in my BC40, they did fit and it did work.

I include the length in my battery test and in the summary you can easily pick the shortest protected batteries.

The specifications for the batteries says they need one and as I wrote above, there are situation where you can damage them.

That's what I read from the spec sheet:

2. The Overdischarge Safety Function

The discharge stops when the voltage per cell falls below 2.3 ± 0.1 V.

As for my torches they won't run below 3v (Solarforces) and my BC40 won't run under 5.5V. So for me I don't think the protection is going to kick in.


I am presuming it's the length of the battery that is causing me the problem, but you could be right. The only problem is the only cells I have right now are 2 Trustfire flames. But I do have 2 Sanyo 2600 un-protected on the way.


But if you somehow developed a short etc. in the light or if a short developed outside the light or your charger went haywire or many other scenarios you may be glad they have protection, I can only see protection as a good thing, not a bad thing, as long as a quality protection PCB is used.

I agree, I am not saying it's a bad thing, just maybe becoming a little more redundant as these cells become more user friendly. Just thought I would air my thoughts and see what came back.


The cells can't "regularly" be deep-cycled that low without adverse effects. The protection circuit is an added (redundant if you will) fail safe protection against over charge and over-discharge.

as mentioned - Li-ion protection is three fold:

1) minimizes chance of an over charge by charger (a safety concern to user/family/belongings)
2) minimizes chance of an over discharge by the user (a longevity/health of cell - which most believe has minimal effect on longevity)
3) minimizes chance of a short circuit (a safety concern to user/family/belongings)

devices that have an auto cut off is to prevent overdischarging of the battery only,
this does nothing for the over charging or short circuit SAFETY concerns.


If your battery is used absolutely exclusively using dedicated charger (good ones) and protected light, and used regularly, I see no problem with using unprotected NCR.

Still, if flashlight turn off at 2.3V, I won't depend on that as much protection at all. Discharging that low is not healthy even for the NCR. Total capacity will drop.

My Solarforces won't run on 2 fresh eneloops 2.8v. so they must cut off around 3v. Which should look after all cells. When charging I always use my DMM to check the voltage, as I have a cheap 'travel charger' from DD. (Which works very well by the way). The only thing that would would concern me is a short. But I can't see that happening. If the electronics in the drop-in shorted I would imagine it would pop in a second. Wouldn't like to find out mind!



Has anyone heard any news on how far away these are??

That is usual the case, the protection is placed a bit below the cells specification.

Ah, OK I get it.

Thanks, Marc.

You need a good low voltage drop in (.8-4.2v) to work well with AA's.

No I wasn't trying to run it off AAs I was just trying to emulate where an 18650 should cut off, to see if the drop in worked as it should.


Oh, OK. Sorry.