Panasonic 3.7v 3400mAh Protected 18650 Length Issues

Before buying these beastly batteries I knew they were long, I measured the length available in both of the 18650 lights I had access to… long story short they are rather squished in my primary light.

I was wondering if there was any issue with the center of the negative flat end being dented on both cells. One gets dented by the positive end of one battery, and the other gets dented by the inside tail switch post.

I stopped using the batteries once I noticed the dents, but if it’s bad to use the light that causes the batteries to get dents… any suggestions on a decent quality 18650 light for <$50 that definitely can use the Panasonics without issue?

Most P60 hosts fit protected 18650's perfectly fine. All my Solarforce P60 hosts especially (L2P, L2T, L2N)

The XinTD C8 from intl-outdoor is regarded as a 'premium' C8, as in, it's the most pricey.

I personally don't own the Convoy C8 from FastTech is significantly cheaper but it has a OP reflector rather than a SMO, resulting in a less tight hotspot.
I'm simply assuming it'll fit a protected battery.


i own convoy C8 from FT and my panny is fit.
69mm :slight_smile:

Is there any issue with using the dented batteries? I can throw up pics if needed.

As far as the C8 goes… there are like 50 different models/parts on FT… Best guess on the best value version? :~

Also, “Group 1 (3-Mode): 5% > 40% > 100%; Group 2 (5-Mode): Lo > Mid > Hi > Rapid > SOS” I’ve never seen a 2 group… function?.. I’m familiar with the Group 2 5-mode, but not with what I am assuming is a combination of both somehow? If someone could explain that to a novice that would be awesome; otherwise I’ll look up a bunch of stuff on my break on Friday. Thanks!

Yeah, the Fasttech protection circuits are really flimsy and chintzy. I have a bunch of pressed in Sanyo 2600’s from Fasttech because the Trustfire X6 has such a short battery tube. The Redilast, AW, and Keeppower cells are a tad shorter and have solid PCB’s for the protection circuits. They are worth the extra money just to have a little less length and a more robust protection circuit.

He was talking about the negative end being dented. The protection circuits are on the positive end.

The protection circuit is nearly always at the negative end on LiIon batteries.

All LiIon does have some protection in the front, but it is not the protection PCB.

I have disassembled a protected battery, where you can see the PCB.

DOH! Typo, yes of course you are right. I’ll fix that in my post.

Since we have the battery expert here, do you see anything wrong with slight dents there? I dont see how its going to disrupt the circuit unless its pretty severe.

I have seen some protection circuit that could be disabled by a dent.

Hmm, my two Panasonic 3400mAh protected cells have small dents on the negative end now because of pressure from the spring cover in a flashlight. Hopefully they’re still ok to use. I would question how they can legally be called 18650 though when they’re clearly almost 18700.

Most protected batteries have a metal disk over the “real” negative pole (bottom) of the battery. So the dent you see most probably is not in the “real” battery. But if you ever dent the “real” negative end of any li-ion battery, you should recycle it and not use it, even if it seems fine at first.

As most know, the li-ion catalyst is in an extremely thin-walled bag which is rolled up very tightly — like a jelly roll — and inserted in the battery tube. If this bag leaks or is otherwise compromised, any number of events can occur, all of them bad. At the worst, you will get a vent-with-flames situation.

And if the venting-with-flames occurs inside a sealed battery tube …. Well, the outcome will not be good. If you are in Pennsylvania, for example, after the vent, you might want to start your search for the flashlight screw-on end cap in — say — Ohio or maybe even Iowa.

Hm, the kind of dent I’m talking about is small dents caused by a charger or flashlight spring cover, nothing traumatic, but a slow pressure application to the end of cheap Wallbuys metal negative endpole protection circuit cover. Do you think this could disable the protection? If so we’d still have a nice Panasonic cell, but not worth it to buy protected from Wallbuys if its so easy to possibly injure the circuit.

I have the same dents you describe. Hopefully everything is ok.

Is the situation worse because maybe your primary light has batteries in series so the size affects are additive?

I dont know about his situation, but my situation with dents is because they do not quite fit in the WPII charger, they should fit in a 3T6 or Warrior fine without denting, as they fit in mine.

I believe I have the same situation as B42; the posts inside the light were somewhat slowly denting the batteries. I went ahead and just put the panasonics in the thor, and am using the nitecores in the little zoomable. So far it doesn’t seem to have effected anything, but I’m being cautious as to not overcharge or overdischarge them.

I’ve dented both my 3400’s trying to fit them in my Trustfire X9. (the batteries it came with had no problem) The 3400’s fit fine in my Ultrafire C1. I have a Small Sun T620 in the mail, we’ll see how that fits them. But I think I’mma just get a better DMM and not buy any more protected cells.