Li-Ion battery charging question

Hi everybody,

I'm new to the world of Li-Ion batteries.

So today I got a bunch of 18650 batteries. When I unpacked them, the voltage on each of them was 3.5V.

Since I want to charge them to 4.1V - 4.2V, and I don't have a dedicated battery charger, I'm using my bench power supply for the trick. I've read the theory, set up my power supply to CV 4.2V and CC 0.6A

When I connect the battery to the supply, at 4.2V the battery is draining only 400mA.

I was hoping it will hit the CC immediately, instead now that the battery voltage is 3.7V it's draining only 0.300mA.

specs: Max. charge current: 4A (Ambient 25°C)

I can get 1A of current if I increase the voltage to more then 5V, but I guess that's not smart.

What could be the problem? Any thoughts ?

High resistance connections? Croc clips are notoriously bad at carrying any real current.

But since your display reads 4.19V what makes you think the battery is only at 3.7V?

Steve

I suggest that the OP go read about charging Li and about the required charging sequence. I suggest putting a stop to using a power supply to charge a Li.

slipstick:
High resistance connections? Croc clips are notoriously bad at carrying any real current.

But since your display reads 4.19V what makes you think the battery is only at 3.7V?

Steve

@slipstick - " High resistance connections? " - Indeed : ) Thanks a lot.

I soldered the croc clips to a much wider wire, and everything works great now. Many thanks, much appreciated.

@Idahowalker - thanks for the replay, but in the end everithing worked great.

When I connect the battery to the supply, at 4.2V the battery is draining only 400mA.

I've used my power supply to charge my 18650's quite often. You have to be sure the power supply displays are accurate.

In the above quote I will assume when you say "draining" you mean "charging"

My guess is your power supply settings are not correct. It should be set a:

  1. Short Powersupply(PS) output, adjust current limit to 800 ma (1a is OK but 800 is better for the battery)

  2. Remove the short and set the voltage to 4.1 to 4.2V Don't believe the meters on the PS.

Now when the battery voltage is < 4.2 the current will be at some number. When the battery reaches 4.1 - 4.2 the current will drop to a very low number (may or may not be exactly 0).

Screenshot 2021-02-20 193848.jpg

Screenshot 2021-02-20 193848.jpg

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