I'm all for simplicity, but it should only take 5 -10 minutes to wire up the BMS and do the initial charge at 12v. Even better if you have a 12v charger that can push more amps. Once you get them mostly topped off (at BMS cutout), top balancing in parallel is quick.
If you look at it in terms of watt hours, it really highlights the speed difference:
- 4 of those 280ah cells hold about 3640 watt hours.
- Traditional parallel balance at 3.25v and 5a, it would take over 9 days to completely charge those cells from empty (you are charging at only 16.25 watts).
- Put them in series with a BMS and use a real 12v charger at an average of 13v at 90a, it would take ~3 hours to fill them from empty (you are charging at 1170 watts, so 72x faster than the parallel approach using a cheap 5a power supply
I think my math is right there. Anyway you slice it, charging these huge cells at 3.x volts and 5a is a huge exercise in patience. Not something I have.