This topic hadnt had an update for some time.
Last couple of months i was thinking of designing a new concept BMS for my LiPos that are packed 8S. Well not one DIY BMS todate has ability to monitor 8S packs in one PCB. There is always a limit like 32V Vmax for controlling chip etc...
So i thought why not join Neville modules and make them 8S with 9 wire connection. That makes for a very simple assembly
I started first model PCB with full +/- connection. Mistake! After balancing when more and more modules started to balance cell value began to climb!!! I got 4.10V when highest cell was 4V! The best explanation was that current was seeping trough wires back and forth and creating residual voltage that showed itself on neighbouring cells.
When i saw that even those cells were balancing that werent trough balancing treshold initially, this confirmed my suspicion.
I need a new design.
New PCBs have default neighbouring connection that require only 9 wires. Certainly i can also connect only 6S or 4S cells.
I dont need resistors anymore. I use TIP122 darlington and i open it with weak base 10K. It can give 2A shunting there. Best thing about this is i can use car chassis as heasink. I just have to use good mica sheets to separate transistors from metal heatsink.
I also planned on using small 8A fuses just in case. However system is designed to monitor cells even if transistors burn out. I would get plenty of notice.
Also i designed new master board that has optical separation built in. There is also separate serial port connection that is allways transmitting.
By all effects this system is still distributed, i just packaged it as a 8S system for difficult to connect cells. Also due to optical separation BMS can be chained for 16S cell packages etc...
I will post new build files later when i try the whole system, but with one 8S PCB working good i am optimistic.