What is the fully charged voltage for an AW 18650 a day after charging?

[tre]

I purchased a better charger (Pila) and some button top 18650 cells (AW 2200) because I now have a few lights that will not use flat tops and I don't like the idea of using magnets. Anyway, the new AW 2200 cells come off the charger at 4.2v but stand at a bit less than 4.1 (crappy analog meter) 12 hours later. I did not put them in a light. Is this normal for AW2200 cells or are my new cells not good? I got these from a dealer - not directly from AW so they may be old. Not sure what is normal with the new charger and new cells.

 

[amigafan2003]

Sound like they are old.

My Pila charges my AW 17670 cells to 4.15v and they are still 4.15v after a day. Drop to 4.14v after a week in the fridge and stay there (only go a few weeks without use normally as I cycle them).

Still sound perfectly ok to use though, you just have a bit less capacity. Do they het hot during charging (the Pila gives off heat when charging normally, so don't confuse this with the cells heating up - check the bottom of the charger and compare it to the cells - are the cells hotter?).

 

[45/70]

Hi tre. If you measure the voltage of a cell immediately after removing the cell from the charger and it reads 4.20 Volts, ideally, it will still read 4.20 Volts 12 hours later. Since Li-Ion cells start aging as soon as they are manufactured however, it is pretty rare for them to do this. Usually, "new" cells will read 4.18-4.19 volts after 12 hours though.

It sounds likely that the cells you received were older cells. Some have said that if you run a few cycles on cells that haven't been used for a while, that the voltage will improve, although I've never witnessed this. Then again, my cells are used on a more, or less regular basis.

Also, while analog meters still have their place, it would be preferable to use a digital meter for this purpose, even if an inexpensive one, as you are usually looking for very small, relative differences here. I'd check the voltage with a DMM, if you can borrow one, and then if the voltage drop is still 0.1 Volt after 12 hrs, if it were me, I'd contact the vendor and see what they have to say.

Dave

 

[tre]

I broke down. New DMM on the way. I did not order a fluke but + or - .5% should be pretty good for testing batteries.

BTW, the last 18650 I charged was hotter than the charger.

 

[tre]

Update: My meter has gone nuts. I tested known good 18650 cells, primary cr123a cells, eneloops, and AA alkaline cells and the readings are all over the board.

Update2: I used an infrared thermometer to check the temp of the new cells while charging on the Pila charger. The 18650 cells are 95 F, the bottom of the Pila charger is 95F, and the part of the charger the cells rest on was 105 F as measured between the two cells while charging. FYI, I left the plastic cover on the Pila open the whole time while I use the charger. That Pila gets warm.

 

[MikeAusC]

The self-discharge for good LiIon cells is effectively zero, so the voltage shouldn't drop with no load, for months.

 

[amigafan2003]

FYI, I left the plastic cover on the Pila open the whole time while I use the charger. That Pila gets warm.

It does. Was it Selfbuilts charger comepndium that recondmended the lid of the Pila be left open when charging?

However, 95f (or 35c in real money) is nothing to be concerned about.