My boombox project is currently designed to have x4 3S4P (11.1v) 18650 battery packs, each will have it's own BMS. x2 on one side (11.1v each and connected in parallel) ) and x2 on the other side (same arrangement). The power feeds a 12v regulator to power a monitor, then converted down for a set of 5v LED strips and RPi4 and then is combined (all four packs = 22.2v) and boosted to 24v to feed two amplifiers. I have calculated the load to be between 4-9 amps continuous.
- Could I plug this into a suitable power supply and charge the batteries (through the BMS's) and use it at the same time? I have heard of some power banks that can do this so I thought I'd just scale it up a little. Perhaps if the battery is only below 50% charge to avoid cc/cv complications. Maybe a solid state relay to switch between using one 'bank' of x2 battery packs whilst charging the other two? This would mean disconnecting the x2 parallel packs (11.1v) + x2 parallel packs (11.1v) = 22.2v into x2 series packs (22.2v) = load and x2 series packs (22.2v) = charge.
- Also, I'm aware that I have to stop the batteries trying to charge/rob/inrush power from each other when connected and have to isolate one bank from the other when charging but I'm not sure how to do it (3 way switch rated for the load?). Biggest concern is how to isolate/bypass the balance wires to stop them trying to supply the load or short circuit when one bank of packs is switched off to charge the other or when each pack is paralleled and each bank is series connected to make 22.2v.