How to see if a battery is protected

Just came from your site. I believe there are some double posts in last group of pics.

Oops, fixed, Thanks.

Fantastic little guide, HKJ. Thanks again!

Nice information to check battery protected or not. Thanks for sharing this useful information

Thanks HKJ.
Will the added protection board cause difference in diameters?

It will make battery longer but the diameter will be almost the same or just slightly larger (~0.5mm or so) because when you add protection you have to use one more layer of wrapping foil because there is an additional “flat” wire that goes from protection PCB to opposite pole and it needs to be isolated.

Usual yes, due to the strip fro plus down to the protection board at the minus end.
Some just add a new layer of wrap, other removes the old wrap or buy unwrapped batteries to start with.

The length of a 18650 cells can be up to about 72mm, but usual is below 70mm

Accepting 19mm diameter and from 65 to 72mm in length will handle as good as all sizes 18650. There is also the issue about flat vs. button top, the extra length due to that is included in the 70/72mm, but remember that on a flattop the isolation can be a few tenths mm above the plus pole.

Some (like Soshine) have their protection on the positive pole and only one wrapper layer. Such cells have the same diameter as unprotected cells.

Want to see if its protected? Short it with 10 gauge or similar cable if it gets really hot or blows up its probably not protected. If it does nothing it probably has a protection circuit.

:open_mouth:
or just send them to mattjk so he could test them by shorting + a - !!!
If he answers after testing = its protected,
if no answer for 24 h or more = it’s not protected and he is in hospital waiting for skin grafting…

Unprotected cells with PTC won’t heat up cables because they limit short circuit current (but I don’t know what “10 gauge” means).

gauge (AWG) is the measure the yanks use for the cable size. 10 is good for about 50 amps depending on length

And yes i was obviously kidding!

Actually, Sony did that when they were conducting the required Engineering Testing when they invented these batteries. Not with wire, but with a “dead short rig”.

Those early batteries must have been made better than the “modern” ones, since all they did was discharge to some low-low voltage & get hot.

So, all the fear-/belief-based hype and hysteria is great fun, but reality has a tendency to be far more boring.

You forgot “vent”, this will often happen when batteries gets hot and it is only a problem if there is a spark.

Uh, no, I merely quoted their publication of their results. And they also recorded the actual highest temperature (I would say “QUITE hot”) and the fact that there was no venting or bulging or other failure.

The only evidence I can find of “venting” (with or without flames) is on youtube videos, where the actual rigs used to create the desired result are poorly or falsely “documented”. Which is why your measurements, HKJ, are so vital to posterity.

Usual tests are passed with “no flames and no explosion”, i.e. venting is acceptable.

I have had a few batteries vent during test when they got too hot and when I notice the venting I include the information in the review, but my guess is that I have missed some vents (They are not dramatic in any way).

I forgot to say: Except if they happens in a airtight flashlight.

Thank you for explaining.

Awesome …thank you so much HKJ!

Here is more information of gauge and voltage drop for your reference.

Very professional post. I learn.