Basic battery capacity question

[JlightT]

I have some 16340s, some of which are a bit old. When I charge them to full capacity and put them on a voltmeter (tested across 2-3 voltmeters), I'll get readings like 4.1, 4.13, etc

When I put them on my new Mini MBT, these same batteries read as 80% or even 60%. Is there something wrong with my MBT? Or is it because the pulse load the MBT puts across the batteries can make old batteries sag? IOW, do I believe the voltmeter or MBT?

This does not seem to happen with some of my 16340s that I believe are a bit newer (but still probably 3-4 years old), the MBT considers those batteries 100% when they come off the charger. Leading me to believe I might have very old 16340s that are sagging under even a small load. Does this explanation make sense?

 

[Voider of Warranties]

I haven't used an MBT, but it sounds as if it does the same thing as the contraption that I rigged for my DMM in order to test a battery under load. Testing under load will give you the "true" voltage so to speak. It sounds like you've got some tired old batteries.

 

[JlightT]

Thanks for the reply! Yep I should do a better job of writing down when I get batteries... some of these batteries might be 5-10 years old, I just don't k now which. Or maybe now I do, the ones that the MBT thinks are only partially charged even fresh off the charger

 

[aznsx]

Thanks for the reply! Yep I should do a better job of writing down when I get batteries... some of these batteries might be 5-10 years old, I just don't k now which. Or maybe now I do, the ones that the MBT thinks are only partially charged even fresh off the charger

I just mark mine with a Sharpie - mmyy. That can rub off, but mine don't seem to get handled enough that it's proven to be a problem. If it did, I'd just mark over them again when they got faint, but don't recall having to do that. Might not work well with all-black cells, but practically none of mine are all-black.

 

[Voider of Warranties]

I just mark mine with a Sharpie - mmyy. That can rub off, but mine don't seem to get handled enough that it's proven to be a problem. If it did, I'd just mark over them again when they got faint, but don't recall having to do that. Might not work well with all-black cells, but practically none of mine are all-black.

They also make silver Sharpies that I use on black surfaces. It seems more paint-like than black Sharpies.