arduino BMS flying cap, LTC8604, TI BQ76940

Of course there are cheap chinese BMS, I have few, some are not even working on cutting off voltage. 

And I don't think cutting off should be job of BMS, a good BMS should :

  1. monitor voltage with out dran out current with divide resistor
  2. not bound to chemistry, could be Lipo, Life..etc
  3. monitor temperature of each cell or connection
  4. able to communicate wire or wireless
  5. Better to be sleep



 https://www.instructables.com/Arduino-LTC6804-Battery-Management-System/

Base on LTC6804, SPI interface. The BMS is configured for a battery pack are composed of A123 LiFePO4 cylindrical batteries in 12S8P configuration. The A123 cells have the following characteristics:


LTC6804 can monitor upto 12 cells, wih arduino lib https://github.com/dcaditz/BMS_V4

and could be available as PCB from tao

Another good code, with presentation on 6804

https://github.com/ayushagrawal/BMS-Arduino

not sure what is the difference on 6802-1, it works also on 12 cells. 6802-2 could be addressed 


There is a newer version LTC6813 on 18 cells, but chip is more difficult to get


There is also TI 76940 (also 30/20 but less cell counts) at 15 cells with IIC interface also available from Tao

arduino lib https://github.com/LibreSolar/bq769x0-arduino-library


after more search, seems LTC6802 is cheaper and having more shared source, but also a older solution.

https://sourcelion.wordpress.com/2014/07/20/battery-management-system-ltc6802-arduino/

https://github.com/PowerStat/LTC6802



newer post:on BMS

https://www.digikey.tw/en/articles/why-and-how-to-use-battery-management-ics-for-stacked-cells


concerning the stock on JL PCB 6804-2 seems to be a good start.

6804 is a 5 V at Vreg chip

6804-1 can be chainned, 6804-2 can be addressed.
and LTC6820 is a isolation interface chip for SPI
6802 works at min V =10V

Flying cap

There is a old school way using arduino ADC and "flying cap" to measure different cell, very interesting

relays with 10uF flying caps,The low-power relays are only activated for ~30mSec.

The chip used is a TPIC6C596, used to select which cap connect to ADC

I did a single cell test with what I have on hand, it works, but need to work out the Vref







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