I'm planning to use a 4s 18650 LiPo pack to power a portable speaker and I'd like to include a charging circuit, so I don't rely on an external balance charger. I currently have it hooked up to this HX-4S-A01 protection board, which apparently lacks balancing features.
Am I fine, if i just add such a balacing module and hook it up to a 16,8V Power Supply, or do I need a different module e.g. to limit current?
Would this module alone do the job of protecting, balancing and charging the batteries?
I'm a bit lost in the different types of protection and I appreciate any help.
Best Answer
First of all, I think these 2 videos can help you a lot:
But back to your question:
As far as I can see from the AliExpress page, your current board is based on and S-8254A IC, which has plenty of security features:
However, as you said, It lacks balancing. It is mainly a protection board to avoid anything going bad but It is not recommended as your only option for charging and discharging circuit.
If you use a power supply that has current limiting everything becomes much easier, you just have to set the voltage to the maximum voltage of your pack (4*4.2 = 16.8V) and the current of supply to something manageable like 1C. If you lack this feature in your supply, there should also be no much problem, as long as the S-8254A IC measure any of your cells is higher that 4.2V, it will put the boards's MOSFETs into high impedance and will disconnect it from your supply. This way, your balancing board will act alone to reduce the voltage on this cell and when It drops below a certain threshold, the S-8254A will restore connection and continue to charge the other cells. If you have a really high power supply, that would damage your cells while charging due to overcurrent, It is recommended to add a series low-value resistor such as 1~10R, but as long as you have like 2.5Ah cells and an 1A power supply, everything should be fine.
So, If you use these two boards in combination, you can achieve a balancing circuit with a simple constant voltage power supply, the only factor that is out of your control is the all cells will always be balanced at exactly 4.2V, no lower and no higher, but I think this is no bad for your application.
This module would have everything you want in just one board, but keep in mind that its charging/balancing process would be exactly the same as the previous 2 boards combined: all cells would charge together as long as one of them reaches the 4.2V, then the charger would be disconnected and this higher voltage cell would be discharged through a "bleeding charge resistor" (which is what your balancing board does) until it passes a certain threshold to be not considered charged anymore, and then all other cells get back to charging.
Important to emphasize again that in both cases your "balancing circuit" only works as long as the cells are charging and reaches 4.2V. So if you have cells at 3.8V, 3.7V, 3.6V and 3.5V, none of your balancing circuits will work. They will only kick-in as long as your device is charging and the first cell reaches 4.2V.
I hope I've made myself clear ;) any questions...