Newby questions about charging and batteries - is it NORMAL for batteries to be a lot hotter on discharge rather than charge ???

Batteries and Chargers Chargers
1

Hi guys.
I’m pretty new at this hobby, but have been doing some readings in here for quite a while but I have a few questions.
I have been given a full box of old laptop batteries by a friend from a computer store and I have been harvesting quite heavily lately. Some of them are pretty old, from the battery model some were operating in laptops that are 8-10 years old. Others are “newer” but nothing younger than 4 years I think.

I decided it’s good to have a analyzer/charger around so I purchased the LiitoKala Lii-300 and I am pretty happy with it. Decent build quality ( the plastic seems pretty sturdy ) and the features are great.
How to the analyze thing work - you put the batteries in the charger and select Discharge - now the charger doesn’t discharge right away but first tops off the batteries, then starts discharging to 2.8 - 2.9V while measuring the capacity and then re-tops the batteries so in the end you have a full charged battery and also have the capacity on the display.
Now …as far as current goes - I only have the option of selecting either 500mA or 1000mA but this is just for the charging part, the discharging part always takes place at 500 mA.
I always went on with 1000mA to save up some time considering I have about 40-50 batteries to go through.
My observation is that the batteries get pretty hot while discharging ( @500mA ), I can still ( kinda ) hold them in my hand - and slightly warm when charging, although the charging current is twice as fast ( 1000mA ).
Is this normal ?

If the batteries get hot on a 500mA discharge, what happens when I use them in a light that’s drawing 1A - 2A ? Is there any danger in using them in a torch ?

Regarding batteries … as I said, some of them have probably been resting for years and years.
After I take them out of the big laptop battery I check the voltage with a DMM. Some older ones are under 2V so I put them aside and plan on recycle them at my local supermarket ( they have a huge box to collect old batteries ).
Some newer ones have over 3V and are in good shape. Some are at about 2.5 - 2.7V but I bite the bullet and tested those as well and noticed they quickly jumped to 3.2 - 3.3 in just a few seconds after putting them in the charger. My best ones are some ICR18650-28A Samsungs - which turn out to have a 2200-2300 mAh capacity which is not bad at all considering they were made in 2010 ( according to the code on them ).
Roughly all Samsungs are good - they all come close to the 2000 mAh mark ( even some pink ones from 2008 ).
One particular odd thing happened to one green ICR-22F Samsung - after a complete cycle - the charger indicated a total capacity of 2975 mAh. Is this even possible ??
I also found some green Sony and these tend to get a bit hotter while discharging compared to my Samsungs.

Is it dangerous to try and re-rive batteries that are under 2V ? I understand their capacity may not be all that great, but is it dangerous to put them in the charger due to their low voltage ? I have a friend that told me not to recycle as he wants to try and use them as is. I can offer to give him some good ones ( I have to many as it is ) but he still insists on trying the old under 2V ones as well :laughing:

Any inputs are greatly appreciated.
Thanks

2

Yes.

3

Not necessarily.

I too prefer laptop pulls. For all cells I pull from laptops, I refuse to charge them for the first time indoors. And for that first time I use an old “dumb” charger that doesn’t mind if they’re under 2v — it just shoves in enough Coulombs to get to 4.2v and stops. I do this outdoors on concrete away from anything I don’t want splattered with LiIon shards (although I have yet to see any problem) inside a metal cookie tin. If they pass this “smoke test”, I check the voltage periodically for a few hours, then a day later. If they’re still “hanging in there”, they get to come inside & join the rest of the family. Sometimes I can watch them self-discharge as I measure the voltage. Any that don’t pass this get dumped in the recycle bin when I’m looking for my next pack to crack. I give a lot of the good ones to friends for whom I’ve bought/built/upgraded torches; and since they’re friends, I’d never dream of giving them an untested or unusable 18650.

PS: Welcome to BLF!

4

It is not the battery, but the charger that heats up during discharge. This is inevitable as the energy in the batteries has to go somewhere. The charger dissipates it as heat.
An 18650 battery doesn’t warm up at 500mA discharge current.

5

Ask him if he knows when not to inhale.

If he doesn’t know the answer to that,

ask yourself how much you’d miss him if he were no longer your friend.