How to change number of cells?

[twanek]

Hi!

I managed to get some output with a Due, but my modules are S7, not S6 (it is from Mercedes C class).
The problem is, that in your version the number of cells are only up to 6, so I get wrong values for AVG, min/max, etc voltages.

Can you please advise, what is needed to change in the code to read all 7 cells? It is enough to change all the "for cycles" to 7, or it needs some additional hex address, etc in the protocol?

Thank you,
best regards!

[twanek]

Hi again!

I made some more tests, printing detailed info about the module, and there is some strange thing going on:

I have only one module connected, but the Due always finds 2 modules. Regarding the cell voltages, on the "Pack status" it prints for the "first" module 4 correct values for the cells, then for the "second" module it prints 3 correct values for the rest of the 7 cells of the first module...

Also, for the temperature, AFAIK, the module has only 2 temp sensors, but it prints 4 different temp value, 2 for every "module"...
Attached there is a log file and few photos about the BMS, the version number is readable, so you can understand better what I'm trying to explain. There is only 1 module connected!!!

log for bms v02, 7s, 617647baud.txt

Can you please look into the log file, what can be the issue, why it finds 2 modules instead of 1?

Thank you!
best regards,

[daimlerman]

The module in the pictures are definitely from a MB B- class.
Manufacturer module specs are; 2.3KWh of usable energy content; low voltage limit 17.5V; high voltage limit 29V; 308 cells
I am not sure what chemical composition for the cell is, but I would not discharge them below 2.8V (19.6V for the module).

[twanek]

Thanks for the info!

Indeed has 308 cells, it is a 7s module. I never discharge it under 3.0v, usually 3.1v. Anyway, under 3.1v there is nearly no energy at all, the voltage drops very quickly. We use 4 modules like this in parallel, to power our motorhome.