New 18650 Charger not working, how to test?

[Superorb]

I just received some protected 18650 cells and a charger. I hooked the charger up through a Kill-a-Watt meter, but it's pulling 0 watts and 0.01amps from the outlet. This charger is supposed to charge at 1A per channel (2 channels). How can I monitor with my multimeter while it's charging the cell? What setting to use on the meter?

 

[SilverFox]

Hello Superorb,

It looks like your charger is drawing 0.0012 kilowatts. Working backward to 4.2 volts, I believe that works out to a charging current in the 3 mA range.

If you connect your volt meter to the + and - terminals of the battery you should be able to monitor the charging process. The cell will read 4.2 volts when at about 85% full charge, all the way to 100% full charged. It usually takes 45 - 60 minutes to go from first reaching 4.2 volts to a full charge.

Tom

 

[Superorb]

Thanks Tom. Since the input is 500mA max, shouldn't it be pulling more from the wall than 0.01 amps? I had the meter on it while charging and the volts looked correct, is there a way to measure charging current in mA with the multi meter vs. the wall meter?

 

[tsmccull]

P=EI; I=P (1.2W) / E (4.2V) = 0.286A or a bit under 300 mA. A 300 mA charging current at 4.2V only needs to draw 10 mA from the 120VAC. This doesn't take into account efficiency, but unless you have a very accurate meter, the 0.01A wall measurement is probably only approximate. The suggested 1 amp into the battery also may depend on the state of charge; the charger may be throttling back a bit if you put a cell into it which already had a good state of charge in it. It may be working fine. Try a nearly exhausted cell or two and see if you get .02 or .03A or a bit more from the 120VAC in that case.

 

[Superorb]

The suggested 1 amp into the battery also may depend on the state of charge; the charger may be throttling back a bit if you put a cell into it which already had a good state of charge in it. It may be working fine. Try a nearly exhausted cell or two and see if you get .02 or .03A or a bit more from the 120VAC in that case.

That makes sense as the cell was already up to 4.10v when I stuck it into the charger. I'll check once the cell is more dead.