18650 battery Question

[XERTYX]

Ok. So in the "Can you make your own lithium batteries?" Thread I learned quite a bit about lithium batteries and BMS balancers and so forth. I you're familiar with my posts in there I have a broken USB battery bank with solar panel that has 5 matched 18650 batteries in and I want to make use of them.

Yesterday someone gave me 2 vape box mods that arent working and I decided I wanted to play with them and see if I could get them going. One of the vape boxes is completely dead and the other just wont run an atomizer anymore. The dead one has an 18650 battery in it and a spare battery. The one that turns on may but it's not removable unless I disassemble it. Then I remembered I had another high quality one that my nephew gave me. So I dug it out. It also has an 18650 battery and charges via USB. 

Now I know it's not wise to mix batteries and I dont intend to. But I have 5 matched ones from the USB battery bank.

Here is what came to mind when the lightbulb went off over my head once I realized I had an 18650 charger. Amazon has a simple 4S 18650 battery box like the ones radio shack used to have to hold 4 AA batteries in series for science fair projects etc.

So is there any imminent danger from charging 4 of the matched batteries 1 at a time in the charger and then putting them into the 4S adapter to run low DC loads like an LED light and USB charger?

Should I mark each of those 4 cells with sharpie A B C D and their corresponding locations in the battery box so they will always be in the same configuration when I've charged them?

Should they be marked and rotated around every charge to help balance them?

Sorry if this is a stupid question but it seems like a win if this would work and make some trash useful again. It also seems like they wouldnt need any balancing as they would be recharged independently of one another but lithium is like ancient greek to me and I know it can go boom so I'd rather ask.

I've always heard it's better to remain silent and be thought a fool than it is to open your mouth and remove all doubt, but here we are.

 

[tx2sturgis]

You would have to monitor the cell voltages (or the overall voltage) in the series string. If one of those cells discharges too low, it could damage it.

I have in mind a similar DIY project, since I have a few surplus 18650s lying around, but mine will have the cells in parallel, simplifying the 'telemetry'.

 

[XERTYX]

But in theory if say I recharged them separately every day and didnt discharge the 4S bank too deeply it wouldnt pose any risk of fire? The only danger would be damaging a battery that would otherwise be trash?

 

[Wabbit]

... it wouldnt pose any risk of fire? The only danger would be damaging a battery that would otherwise be trash?...

That's probably not a super correct conclusion. Here's some reading if you have the time.

https://batteryuniversity.com/learn/archive/lithium_ion_safety_concerns

 

[tx2sturgis]

If one fully discharged cell gets 'reversed' (cell reversal) it will be headed for the junk pile, but I don't think it is at risk of spontaneously catching fire. It might bulge or possibly leak...if left in the circuit. Either way, your device will not be working long before this happens so that should be the signal that something is wrong. Starting out with 'matched' cells that are close to the same age and usage, should be done to minimize the effects.

In fact a truly dead cell has little or no stored energy to cause a fire, (unless you physically damage or puncture it). You would have to attempt to 'force charge' it and you know, that's never a good idea.

Of course, with any DIY project, no one else can say for certain what will or won't happen.

 

[XERTYX]

I'll look thru the link in a little while. Thanks for that.


Yeah I suppose that is true it would be more likely to catch fire if it were overcharged than undercharged. But then again. I know very little about lithium other than all of the salts on the periodic table react violently with water. In high school we got to go outside after a rain and observe elemental sodium and elemental potassium and how they reacted when thrown into a puddle of water. CRAZY violent exothermic reactions.


Yeah no one can say in a DIY project what could fail. Too many variables. The cells are all the same age and capacity. I wont shed a tear if they become unusable. I just wanna know the likelihood of a catastrophic failure given this specific scenario.

 

[highdesertranger]

I have no idea about your issue but I have some info about 18650 batteries.

I have been trying the last few years to upgrade my battery powered stuff to use 18650's. what I mean is I won't buy a battery using device unless it uses 18650's. so it was going good new headlamp check, new camp lantern check, new flash light check.

then when I was trying to quit smoking I bought one of those vape thingy's and of course I bought one that takes 18650 batteries. guess what those 18650's did not match mine, they were shorter. the batteries were not interchangeable.

I took it back and the guy insisted that his 18650's were correct 18650's and all my other devices were wrong 18650's. BTW all my other device are fine and all the batteries interchange. he didn't even know what 18650 stood for that it was the physical measurement of the battery. so even when I showed the guy that his 18650's were not 65mm long he still insisted his were correct and mine were wrong.

just a little FYI and something to be aware of.

BTW I did quit smoking and his stupid vape thingy had nothing to do with it.

highdesertranger

 

[Wabbit]

/\Congratz on the smoking!! I did it with a ecig, and it was still a rough 1-2 weeks with cravings still popping up 5 years+. Today I am ciggy free and they taste like crap, but without the ecig, I'd still be smoking.

Vaping is not "safe". For me vaping is harm reduction, I don't kid myself about how safe it is to inhale anything into your lungs.

 

[B and C]

Congratulations. I know I need to stop but just keep on puffing away. I might have to try chantix and see what weird side effects I get.

 

[XERTYX]

 ...when I was trying to quit smoking I bought one of those vape thingy's and of course I bought one that takes 18650 batteries.  guess what those 18650's  did not match mine,  they were shorter.  the batteries were not interchangeable.
....
just a little FYI and something to be aware of.

BTW I did quit smoking and his stupid vape thingy had nothing to do with it.

highdesertranger

Thanks for the info. I hadnt considered that. The quality one I had stashed away in a drawer is a kangertech. Pretty good name brand. It has an IMREN battery in it.

After reading your post I checked and they are the same. And I suspect kangertech is aware there are shorter batteries out there as this one has a pretty long spring loaded plunger on the negative terminal.

I dont have a multimeter at the moment so I cant check their state of charge but they wont power on the vape box. I'll try charging them with it tomorrow.

Congrats on quitting. It's not an easy task. Oddly enough I only started smoking 4 years ago.

 

[jonyjoe303]

if your trying to make a 4s pack, you can get a 4s balance connector and a cheap lipo alarm(less then 5 dollars) and connect it to your battery holder. Once one of the cells gets to the lower limit alarm sounds. This way you won't have to worry about discharging the battery too low. 

But a 3s pack would be closer to the 12 volts you need.  3s will easily run fans. You can mix and match 18650 but if you trying to build a battery pack you want each cell to be close to the same mah. The matched cells you have might not even be that close together unless you have run a capacity test on them. Normally a bms will monitor for low cells during discharge. 

No need to place cells in the same slot everytime. The only thing I mark is the capacity of each cell, that way you use 4 cells that are close in mah to each other. The battery pack will be the capacity of the lowest cell. 

The only danger I see is inserting the cell backwards in a slot. You can always put fuses between each cell just in case.