Problems charging Li-ion

Thread Starter

Zeebit

Joined Nov 8, 2013
72
I have a couple of 5300mah 3.7v li-ion cells and I have a few problems charging these. I have discharged these to about 3V. I then connected them in parallel and the resting voltage is about 3.4V.

I am charging the cells using a DC PSU. I have tried it on both an old BK precision and an Agilent. I forgot the model but the problem is the same when I use either of the two.

I charge the two cells in parallel by setting the voltage limit to 4.2v and initially setting the current limit to 500mA. When I hook up the cells, the psu goes to CC mode as expected. However, when I increase the current limit to around 570mA the supply would switch to CV mode.

I don't understand why this happens.

I tried adding a 1N4001 diode in series to each cells. I then set the current limit to 1A and voltage limit to 4.9V. When I hook up the cells, the supply goes into Cc mode as expected.

Why does this happen? With the cells alone, the supply goes to CV when the current limit is about 570mA but when I added a diode it goes up to 1A.

The cells do not have a protection pcb.
 
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