All right so I have an interesting issue. I have two flashlights that use proprietary 2x 26650 2S protected packs. After one literally vented during a bad turbo abuse session cause it couldn’t take being hammered electrically/thermally repeatedly on a regular basis for months on end, I decided to try and solve the battery replacement issue in a dirt cheap manner by getting two BAK N18650COP cells (unprotected of course) and using contact spacers (the ones sold by Li-ion Wholesale for $1) plus some cheap plastic 18650 to 26650 cell tube adapters. Well the cells and spacers came in yesterday and while I did get far brighter peak output than with the stock batteries, I started having thermal issues with the batteries themselves. Namely, these things get flaming hot (enough to be painful to hold) cause they have no thermal contact to the handle, and they both produce heat during discharge and also absorb heat from the tailcap spring and the obviously hot head of the flashlight. Now yes I know I could invest in 26650s and still make it out cheaper than the crappy OEM $35 packs but finding good 26650s is hard and these BAK cells absolutely deliver in everything high drain I have. Current containment for the issue is periodically removing the cells from the light to cool them down and the light down, but even with that this is a little sketchy to be honest and for sure will reduce the useful life of thse cells. I do run the lights on top of a powerful fan now too but that doesnt help the battery thermals much due to the lack of thermal contact to the handle. Soooo with all that being said, are there battery adapters made of thermally conductive materials that can conduct heat away from my cells?
What’s the light? I don’t think shedding heat to the environment is going to solve your problem by an enormous margin if you’re exceeding the current capacity of the cells… Mooch rates these as 25A continuous, I’m curious what light you’ve got that’s drawing more than 185W…?
21700s with a spacer might be more suitable, the current top contenders can do 40A (though it’s a thermal rating, so if they get too hot, they’ll also run away)…
The lights are both those Kodiak Kolossus lights you can get at Walmart (yes I know not enthusiast lights per se, but I like COB LEDs a lot). I am aware of the Mooch rating of course. Haven’t measured the current with these cells, but with a new and full OEM pack (tested a long time ago) and decent quality meter probes I was getting like ~12.5A max and I abused this same model cells to hell and beyond in a vape that draws over 25A with no issues other than waste heat from the vape itself, a little from a 20700 conversion battery adapter and minor cell warmth. I’ll measure tonight with even better probes/meters and see of the current is that much different but I doubt it will be
Planning a similar thing.
I’m trying to slice a 2mm slit on a 22x19mm cooper tube to try squeezing it inside a Z1 tube.
The plan is to wait a spare Z1 to arrive, pre-squeeze the cut copper tube with a clamp and mallet it on the Z1 21.8mm tube using thermal grease.
A cooper tube would be massive and heavy for your flashlight, but an aluminum one could be feasible.
This.
With my hotrods, I find that the batteries are cooler if insulated from the rest of the light, which reach a higher temperature than the batteries.
If the batteries are getting hotter than the light, the setup is hazardous and you need to rethink it–reduce the power consumption or use proper batteries rated for that power. Take the vented cell as a message of caution.
Update: used 25A rated premium probes (got them off some amateur radio seller a while back and they are superior to normal junk) and the lowest resistance meter I have (cheap but internally overbuilt unfused multimeter, my higher quality main one has a fuse and more resistance) and I get like 10.58A peak on turbo. Assuming ideal situation with no voltage sag from the cells, 8.4*10.58 is 88.872W best case scenario with the meter in series. Even accounting for reasonable performance loss amd reduced amp draw due to meter/probe resistance there is no way I am overdrawing these cells. Ughhh I wish they didn’t design these lights to literally dump waste heat into the positive battery terminal. Probably some dumb design to make those fire hazard OEM packs go bad sooner lol. I chain hit this same cell model in a vape mod from full to empty with minimal breaks at 15-20+A and do not have cell-related thermal issues at all. I guess I have to be careful to keep the cells at sane temps and possibly consider buying 26650s or some other solution in the future. As for metal battery tubes, weight is not a concern but was more curious if anyone knows where to buy them cause I’ve never seen those for sale.
It doesn’t completely line up with all of your questions, but 2 years ago Mooch (battery expert) and I had an interesting discussion/conversation about battery temperatures in regard to battery adapters.
You can find the discussion/conversation in this topic:
Interesting… Exactly what I thought. My adapters basically are plastic 26650 size tube with little ridges to hold the 18650 in the center of it so the insulation effect of the air is pretty bad. So far I’ve found if I slightly reduce how hard I hammer the turbo and then pop the cap a couple times during discharge to blow into the tube until the air coming back out is no longer hot helps quite a lot haha.
I did a bit of checking and it seems polycarbonate Lexan is the go to for heat dissipation. Polycarbonate will take a cold bend so you could bent a sheet around into a tube. Tubing is sold by internal diameter and pipe is sold by outside diameter. 3/4 inch copper tubing should work. Copper also has thermal mass which will keep the temperature down.
You’ve got this backwards.
Tubing is typically measured by the OD and most pipe sizes are measured by the ID. Although copper pipe comes in different wall thicknesses and the OD of the different types M, L or K all have the same OD. So they don’t all have the same ID. M is thin wall. L is the most common. K is mostly used underground or for very high pressure applications.
So make sure you look up the ID of the M or L.
Although it is slightly more confusing because there is copper tubing that is made specifically for the HVAC field rather than plumbing and 5/8" copper tubing will have a 3/4 inch OD. But you’re not finding that in the plumbing section at the typical hardware store.
And whether it’s for plumbing or the HVAC field it’s all technically called tubing but in the trades it’s called pipe for plumbing.
But just because pipe sizes are mostly measured by the ID, don’t ever assume any type of pipe is going to be exactly what the size nomenclature specifies it is.
I don’t expect that that cleared things up.
3/4 inch copper pipe that you’ll have in a house or at a hardware store will be 7/8 inch OD. Type M will have an ID of 0.811 in.
Type L will have an ID of 0.785 inches.
I’m documenting the process of switching from 21700->18650 plastic adapter to a inner copper tube on a Convoy Z1:
Nice!