ASIC solution for 20S Li-Ion BMS

[Vindhyachal.takniki]

1. Battery Management System for 20 Serial cells Li-IOn battery. Each cell voltage range: 2.7V to 4.2V with typical 3.6V.
So entire system voltage range is : 54V-84V

2. The system has to be complete BMS, i.e:
SOC(state of charge), Overvoltage/cell protection, undervoltage/cell protection, Overcurrent protection in charging & discharging, short circuit protection in charge & discharging, over & under protection, cell balancing, communication like RS485

3. The best I could get is using combination of TI; bq76930 or this reference design : http://www.ti.com/tool/tida-01093.
This dont have gauging or cell balancing. Gauging can be added using external micrcontroller & programming.
Many other companies had solutions like intersil but its for balancing only.
I am looking some asic for this purpose though. Not one asic but may be combonation of some.

4. Had anyone experience in using some stackable system for this kind of application?

This is query from my client, I have to see if I can design it with some solution?

[Paul Price]

Managing 20 individual cells is in itself a problem requiring 20 A-D measurement points and a way to ensure that the measurement voltage dividers are disconnected aren't discharging all the cells after charging.

Sure, it could be done with lotsa parts. Maybe a single current sense resistor, a 20 A-D input MCU and probably about 20 power MOSFETS  to direct charging/shunts of each cell, then 20 more MOSFETS to switch out the monitoring voltage dividers and some little programming to achieve constant current charging and power MOSFETs to switch in balancing shunt resistors, etc.

The idea here would be to charge the whole string in series at a low current and monitor charge progress across each cell to detect charge voltage inbalances/cell failure and to selectively discharge overcharging cells while directing charge current to those cells still not fully charged.

And then you could interface the monitoring MCU UART to report back charge data with interfacing to a RS485 chip.

Of course you could also just charge/monitor the whole charge process with 20 or so relays to shunt charging batteries as needed.