Possible reason.

GSS · Jul 27, 2017

Only used the battery's in this build. These are button tops so the in series connect between the 2 is good.
Using a NiteCore D2 charger and all seems good.
I won't have a chance to check today.. BobM but curious to what you might see?

Accutronitis · Jul 27, 2017

GSS said:
Only used the battery's in this build. These are button tops so the in series connect between the 2 is good.
Using a NiteCore D2 charger and all seems good.
I won't have a chance to check today.. BobM but curious to what you might see?

Is the prob with the pos term on just one battery or both ?

GSS · Jul 27, 2017

Accutronitis said:
Is the prob with the pos term on just one battery or both ?

Just on the one..And like I said I happened to see maby weeks later??

BobMc · Jul 27, 2017

@GSS, It's something I'm going to factor in when I'm using lasers that use two 18350's. Just keep an eye on it and see. If I run across any that seem to overheat I'll throw them on my Opus and check their internal resistance. Will post if I come up with any thing interesting.

paul1598419 · Jul 27, 2017

The dynamic internal resistance can be calculated. All you need is a multimeter, and low value high watt resistor, like a 4.7 ohm 5 watt resistor, and a calculator. First measure the exact resistance of the resistor. All resistors have a tolerance rated in %....like 10%, so you need to know the exact resistance. Then measure the battery voltage in an open circuit, or rather unloaded. The last measurement needs to be done quickly as it will effect the outcome. Connect your voltmeter leads across the resistor and connect it across the battery. Measure this voltage and record it as well. Your equation will be [Vo/Vl X R]-R=r, where Vo is the battery voltage unloaded, Vl is battery voltage under load, R is the measured resistance of your resistor, and r is the dynamic internal resistance. It will be in mohms, or 1000ths of an ohm. A good r would be under 100 mohms.

Accutronitis · Jul 27, 2017

GSS said:
Just on the one..And like I said I happened to see maby weeks later??

I think that is saying something about that one battery OR something that happened only once since the batteries get swapped around randomly (you don't put battery #1 in first every time), Knowing that would suggest there might be a issue with the pos term one that one battery

OR

Whatever happened only happened one time because it happened over a span of weeks so if it's happened more than once it's unlikely that just by chance it only happened when that one battery was in the wrong place at the wrong time and every time so it left the other battery unaffected by the intermittent prob.

Do you see what i'm saying ?

RedCowboy · Jul 28, 2017

The smaller springs like on the left will get hot if used to carry 4 amps at 5 volts and lose temper, also it will impart heat into the battery, but the one on the right if compressed will make a decent amount of surface area contact spreading the load over more area.

Was it the battery that contacts the spring where it melted? If so you want to get a more substantial spring, I have seen them on ebay.

Search for beryllium copper battery springs that fit your board and solder in a good one.

>>>>>> http://www.mtnelectronics.com/index.php?route=product/product&product_id=385

paul1598419 · Jul 28, 2017

^This is a possibility if you used a small spring as the positive contact for the battery in your host.

Benm · Jul 28, 2017

Springs and high electrical currents are not a good combination in general.

We are all used to springs being in battery compartments for all kinds of devices, but most of them don't require very high currents.

The problem is that the material you make springs off is typically steel, a pretty poor electrical conductor at this point. Even coating it with something better conducting doesn't really remedy that.

Further problem is that springs may get so hot that they lose their tension making things worse.

This becomes a problem if you take a flashlight host that normally takes say 300 mA without a problem, but then decide to ram 5 amps through the existing hardware to power a laser diode. That would damage a spring, a switch, a conductive strip, or anything built for 300 mA use now suddenly expected to handle almost 20 times that.

By analogy it's like having a household extention cord suddenly handling 300 amps instead of 20 - go run for the fire extuingisher!

GSS · Jul 28, 2017

The board on this unit though has a solid contact. I believe its the plastic one that came with the original flashlight. I don't see any distortion or melting on it. The solid contact is on the wider side so my original thinking that the battery's button top positive shifted a bit off the contact because of the wider ID at 19.4mm of the battery tube and long back spring on the end cap putting pressure might not be a issue..
I have some time today to do some testing as far as what I feel as battery warmth.
I'll also try some flat tops which have the wider positive to help with fuller contact?
I'm thinking I just ran longer at one point. The battery's were new, not to many cycle's of charging and showing equal discharge and re charging rates.
@Benn it's a side clicky with the original switch also if your curious..
@Paul, electronic's isn't one of my studies but is there any house hold products like a old DVD player, VCR, etc that I might fined a resister that will work?

RedCowboy · Jul 28, 2017

I have burned out my share of cheap flashlight switches as well, mostly powering 44 diodes, I just go back with a bigger switch and make it fit.

Now I use 26650 hosts and for 35 dollars or so you can get a nice 3 x 26650 host with a better switch such as these, the flared bezel is removable from the finned top on the wider 12T6.

You can make your own head or have one turned by members here such as Lifetime17 and others with lathes, but I like to lean to the sturdy side, the reward is a strong beam with a longer duty cycle.

TrustFire J18 7 x LED 5 Modes Extendable LED Flashlight Torch Lamp Light

Super Bright 13800LM 12T6 12x XM-L T6 LED Vastfire Flashlight Torch Lamp Light | eBay

GSS · Jul 28, 2017

RedC

I have another 44 at 4.5A in a C8 from Lifetime with his nice CU pressed in AL hefty sink

This one run's on 2 18650's which is still not 26650's but I can get another tube and run 3 18650's I think. Also using the Samsung 25R's on it and they do well..
Oh yeah, Lifetime has already told me he would take this C11 and upgrade

but this was my first and even at 4A its pretty brutal and I just can't use them like you do:bowdown:
As of now I can't find an extention tube for this C11 to run maby 3 18350's or 18650's.
Since its a thick cast type of AL host i'm thinking of trying to bore out the tube to fit some oddball 20 or 21 series battery. It might be worth it for a few more Amps??
I'm getting kinda bored laser wise lately so thinking about it..

GSS · Jul 28, 2017

Double post and sorry..
Found something that's my stupidity and un excusable at this point. Both battery's now have a big divit on the negative ends and are basicly at the point of touching each other in series. I noticed it was a little bit when first using the laser a couple years ago and thought that's how they came but should of noticed the divit getting deeper.
The battery's do stick out a bit from the host and the end cap has a long spring and feel pressure screwing it on.
Like Accu had mentioned about using the same 2 battery's you never put them in the same way every time and both looked the same on the negative end. Still a bit strange that the end caps are that thin to bend though.
My stupidity

, wondering how much this has to do with melting issue if I fix the spring tension issue..

BobMc · Jul 28, 2017

Any idea GSS what causes the divots? I've got a couple of 18350's that have the same thing. I've been using battery magnets to take up the slack. They still seem to work fine, just got that indentation. :thinking:

GSS · Jul 28, 2017

On mine it seems to be to much back cap pressure when screwing it on, plus the solid contact on the front board doesn't help. I just have to cut the back spring down some and find the comfort spot. It should help??

BobMc · Jul 28, 2017

GSS said:
On mine it seems to be to much back cap pressure when screwing it on, plus the solid contact on the front board doesn't help. I just have to cut the back spring down some and find the comfort spot. It should help??

I not sure on mine that it's the spring pressure. If so I would be seeing it on quite a few batteries. I'm not, only on a coupe, so I'm thinking something else is at play? But don't know what. ??

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