Charging 18650 battery

[zcramses]

I have a small battery pack of three 18650 batteries in series to get 12V. I need to make a charger for it, where the materials I have are an adjustable DC power source (3V to 18V) with a port of up to 5A and a 3S BMS. The idea is to make a system to make it a CC-CV charger so in order to get a constant current charging of around 0.5C, I thought of using this charging board (https://www.aliexpress.com/item/32711173698.html). Is there anything else I might need in my system in order to get a correct charging of my battery?

I will be using a multitester to verify that I have the correct values in each input/output in the system. So in the end, my system would be: Adjustable DC power source to charging board to BMS to batteries.

Is there anything I could be missing or something that could be wrong? Also important, I want to do some testings on this battery pack so I want to be able to adjust different values such as the constant charging current and such. Money is kind of an issue here and it'd be nice to be able to use materials I already have instead of having to buy a bunch of new stuff or a ready-to-use charger that could be pricey.

 

[amberwolf]

Which specific power source are you using? Knowing what it is may help us help you figure out if it can do what you want with or without additional parts.

Regarding the aliexpress DC-DC, it says "5A" but that is almost certainly dependent on what voltage is at the input and the output, as the total power handling capability is unlikely to be 160W+ without a significant heatsink on there (and I don't see a good way to do the heatsinking). How much actual powerhandling is needed is probably a lot less, but possibly still enough that you would have to lower the current on the output to keep the total wattage within safe limits. I don't know what those limits are, however--the specs the ad gives are for the *chip* with adequate heatsinking (that part of the spec sheet isn't present), not for the *whole board*, which will be lower, since it doesn't have a heatsink.


What is the specific use this pack will be for?

A 3s pack of typical 3.7v-average cells will discharge down to around 10v or so when empty, and be at only 12.6v when full.

If you are using it for automotive-12v stuff, they will typically expect 13.6-14v+, so that battery will always be low voltage for them.

 

[zcramses]

The power source I have is kind of old, Chinese brand; don’t have access to it right now but it’s still working pretty good. It has two couple of ports that one has up to 5A and the other one of up to 15A and goes from 3 to 18V, which one regulates with a kind of control knob but one has to have a multimeter to get to a precise value.

I’m basically only doing tests on the battery pack like effects of vibrations on them and such while they are charging, discharging. I might power a tiny motor of 6 or 12V which use something like 0.3A to 1.5A.