ZTS and 18650, how accurate?

[JayO]

Hello all, this is my first post here.

I have a question for my fellow ZTS battery tester owners (and all flashaholics).
At what indicated percentage do you recharge your 18650 batteries?
My tester reads 40% and my DMM reads 3.6volts w/ no load. Does anyone get the same readings? I would think 3.6 volts would be approaching closer to 10%.

All thoughts are welcome.

 

[JayO]

It seems the recommended recharge voltage for AW18650 is 3.6 volts. This voltage level is indicated on my ZTS at 40%-20%. The meter bounces between the two readings when the cell is removed and replaced.
How would the DMM leads be placed so I can measure the voltage with the cell on the ZTS? Is it possible?

Thanks for reading.
John.

 

[SilverFox]

Hello JayO,

Welcome to CPF.

I am not sure what load the ZTS is using on their Li-Ion test, nor what they consider an empty cell.

3.6 volts open circuit is a good voltage to recharge. Some cells allow you to go lower, but it is not in the best interest of long cycle life to do so. With the ZTS you kind of have to adjust your readings according to your use. There may, in fact, be 20 - 30% left in the cell, but to use it may cut drastically into your cycle life.

To try to measure the voltage of the cell under the ZTS load while testing you would have to figure out a way to get a flat conductor in between the cells + nipple and the ZTS terminal and then attach your volt meter lead to that. The other lead would have to make contact with the - end of the cell at the same time you test the cell.

Tom

 

[JayO]

Hello SilverFox,

Thank you for the reply. This evening I tested the same 18650 cell used on my last tests after having charged it a few days ago. Using a piece of tinfoil and the + DMM probe at the + end on the ZTS and both - probes at the -side of the cell. It measured 100% on the ZTS meter and 3.95 on the DMM. The cell off the ZTS measures 3.95 as well. So it seems this will take some doing to graph open and under load voltages as they correspond to the indicator lights on the ZTS. I believe this will be a worth while endeavor, at least for my peace of mind.

John.