2S 7.4V 8.4V 8A 18650 Charger PCB BMS Protection Board for Li-ion Lithium Battery Cell (5pcs)

12/27/24: I tried non-constant-current supplies but the 8A capability of these bms’ is too much for the 3000mah Samsung 30Q batteries I’m using (which spec 1.5a nominal charge and 4a quick charge. Two in series is double the volts @ same amps so I have to limit the charge current to 4a or less and I’m choosing to set it at 3a so it can drive the pi’s and router when 12v is available.) There is no interruption in supply power when the 12v input is cut off, only a slight change in the voltage from the charger’s 9v down to the batteries 8.4v. orig: These are very small, a little over 1” long. The solder pads are very nice and quite easy to get at with a solder tip plus they take solder very nicely. The two I set up so far worked perfectly. I put them on the back side of 2x battery holders and the solder pads were perfectly positioned to take the wires from the holders tabs in straight runs. Even charging at 8a these only get slightly warm, I didn’t run them longer than maybe 10 min but if they were going to get HOT they would have by then. I’m impressed. I’m using these to make a UPS for two pi02 raspberry pi’s and a Slate router. I feed it from a constant current Drok 5a variable DC-DC converter and this works perfectly. The bms’ sense the battery voltage and apply a charge if needed automatically shutting off once the voltage rises. I am experimenting with what regulator to use to feed the battery voltage to the USB sockets for the rpi’s and the router - a cheap 3a unit may run hot at the ~2a I expect will be needed. Another Drok 5a converter would work but might be overkill. I could not be happier with these.

So far these are great little protection boards. No problems at all. Easy to solder to.

I made two 2S battery packs using these for a 8V hand vacuum. Neither of the packs worked even though I had known good batteries. I gave up and deleted the BMS altogether. I know that has consequences but I only charge for short periods and I am careful to monitor charging. Vac works fine w/o the BMS.

used to repair faulty PCB on wine decanter.