Possible reason.

[GSS]

Running a NUM44 at 4A in a Al sinked C11 host with the SXD sinked seperate with a piece of AL.
I just noticed recently 1 of the 18350 button top Efest's wrapping a bit melted away from the positive end.
I can't say to when it happened or how long of a run I put it through. Can that much heat spread through to the contact board to the battery?
I will mention though even the 2 18350 AW's have a hard time keeping up with this diode, in basic terms could this be an example of just over working these battery's.

 

[Lifetime17]

Hi GSS,
Well all I can say buddy it's Mag Light time full copper . Straight line or full bell . What color you want lol .

Rich

 

[paul1598419]

Hi, Peter, Sounds like too little host/heat sink for that diode. I believe they take about 25 watts; 18 watts are waste heat. You need a larger host and heat sink with two 26650 batteries. Otherwise, you'll be contending with this from now on.

 

[BobMc]

Running a NUM44 at 4A in a Al sinked C11 host with the SXD sinked seperate with a piece of AL.
I just noticed recently 1 of the 18350 button top Efest's wrapping a bit melted away from the positive end.
I can't say to when it happened or how long of a run I put it through. Can that much heat spread through to the contact board to the battery?
I will mention though even the 2 18350 AW's have a hard time keeping up with this diode, in basic terms could this be an example of just over working these battery's.

AW's are known to be good batteries, any chance they are counterfeit?

Have you got any others you could try and see if they start to get warm also?

Have run quite a few 44's off of two 18350's never noticed them getting warm/hot before. Guess it's something I'll start paying attention too. :thinking:

Maybe just a bad battery???

 

[GSS]

AW's are known to be good batteries, any chance they are counterfeit?

Have you got any others you could try and see if they start to get warm also?

Have run quite a few 44's off of two 18350's never noticed them getting warm/hot before. Guess it's something I'll start paying attention too. :thinking:

Maybe just a bad battery???

This actually happened to a pair of Efest's. They perform well considering the diode. I did put it through some longer runs than usual one day but just recently noticed when randomly checking my battery's for their charge. Just the one but assuming it was the first to the board. Didn't notice any unusual heat but they could of cooled down before taking them out.
My AW's i'm 99.9% sure they are legit and work well but don't want to push test them
The C11 isn't hugely sinked but still ok for the shorter runs I do and never felt much heat from the outside anyway's:thinking:

 

[Alaskan]

Is it possible the batts were not tight enough together? A small area of contact can make too high of a resistance and produce heat.

 

[BobMc]

This actually happened to a pair of Efest's. They perform well considering the diode. I did put it through some longer runs than usual one day but just recently noticed when randomly checking my battery's for their charge. Just the one but assuming it was the first to the board. Didn't notice any unusual heat but they could of cooled down before taking them out.
My AW's i'm 99.9% sure they are legit and work well but don't want to push test them
The C11 isn't hugely sinked but still ok for the shorter runs I do and never felt much heat from the outside anyway's:thinking:

Interesting and very curious. It's something I'll have to watch for. I've got a few, better than 4.0amp drivers being driven by two 18350's. Would really like to know what happened to your efest?

You said you push them hard once. How long did you push them for?

I'm thinking it was a battery problem and not a driver over heating, because if they were over heating they would do it on 18650's also. Will have to test mine after use to see if the batteries start to get warm. Thanks for bringing this up. Let us know what you find as I will also.

Alaskan had an idea about not enough surface area making contact, it's diffidently a possibility. :thinking:

 

[Benm]

I'd suspect contact resistance to be the problem too.

At these currents just mechanically pushing a contact onto a plate isn't exactly a sound electrical connection, and it could heat up in some parts but no in other causing the deformation of the contact point - with the cell internally being perfectly fine.

It's also something easily missed: by the time you remove the cells the heat will probably have disspated to the point where you no longer notice it.

There is little do about it apart from increasing contact pressure really, or perhaps putting some very conductive and malleable metal in the gap (gold leaf perhaps, it's not that expensive for very thin sheets, and being 24k gold very soft).

 

[RedCowboy]

Even if you have a battery board spring with a small contact area, it will get hot and lose it's temper increasing the problem.

 

[Alaskan]

I had a spring do that to me too, got hot and lost most of its tension.

 

[grainde]

Have you checked the capacity of your batteries and how do they perform under load ie do you see the voltage sagging significantly? Try to measure the internal resistance, if as you say your batteries are having a hard time keeping up, it might be that they are nearing the end of their life. If you have a high IR they will get hot quickly at these loads.

FYI the only time I managed to melt the plastic on an AW IMR was when I short circuited it accidentally with a Nd magnet. It instantly smoked and some liquid leaked out. Funnily enough it still worked fine after cooling. :beer:

 

[GSS]

When mentioning not holding up to well, i'll estimate after 10 runs of 20 to 40 seconds they will go from a full charge of 4.15V to 3.6V? The cells are new and maby 20 recharge cycles?
The board contact is solid but i'm thinking there might be to much battery pressure now that you guys mention it. This is a side clicky host and the 2 battery's stick out a bit from the back of the host and the end cap has a long spring.
Liking this host with the side clicky and feels hefty but also i'm not sure if this is a C11 copy. It's a thick cast type of AL with some type of powder coating. The ID of the battery tube is about 19.4mm which could give a bit of to much play and the long back cap spring pressure could be causing the positive end to slide of the board contact just a bit.
Oh yes Grainde..iv'e shorted a few cells and on one 10440 Ultrafire the wrapping melted half way off Still works too:can:

BobM, I might of run it 60 seconds at one point but being a kinda thick unit it was hard to feel any inner heat??

 

[BobMc]

Have you got any another 18350's you could fire up for about 30 seconds and see if the front battery gets warm/hot? :thinking:

 

[GSS]

I could use the other one in this set of Efest's as the one that melted isn't all that bad "yet"??
I also have some flat top's that just might work well even if the battery goes a bit off center.
Really curious if its a heat issue though.

 

[BobMc]

I could use the other one in this set of Efest's as the one that melted isn't all that bad "yet"??
I also have some flat top one's that just might work well even if the battery goes a bit off center.
Really curious if its a heat issue though.

Very curious myself seeing how I use lots of two 18350's in my builds? Would be a major bummer if I had to change my builds. I will be testing to see if any of mine heat up when in use. I have different brands I can try and test. If I find any that heat up I'll post the information.

 

[Accutronitis]

You might want to double check all your contact points and more to the point the contacts the come in contact with the positive ends of your batteries.....

Do you use those batteries exclusively in that laser ?

Also could there be a contact prob with your charger ?

Bad contacts can make a massive amount of heat which can if left unchecked lead to thermal runaway where in a bad contact makes heat, the heat makes the contact worse, the now worst contact makes even more heat, And you get the idea.....