Guru
Joined: 08/02/2015
Location: New ZealandPosts: 1204
| Posted: 09:20am 18 Jan 2026 |
The "flying capacitor" system uses 0.1% resistors and 1 common ADC input. I calibrated in software using a fluke meter and known PSU in place of a cell. If its within 10mV thats ok by me, as balancing is only occurring above 3.5V per cell so well into the voltage rise part of the curve.
The individual 08M2 chips are using same 0.1% resistor divider and internal 2.048 reference, they seem to be reasonably close in accuracy, so no extra calibration required. I am not too worried with absolute 1mV deviation, the cells only spend a short period being balanced by the resistive loads, before system switches to a lower "Float" voltage.
Way I look at it is as long as all cells are within 20-30mV deviation then they are balanced, at the top end of their voltage end point.
I did look at using a voltage ref IC for auto calibration, but the Picaxe Basic being integer based and limited to 16bit maths make it too difficult software wise; your use of atmega 328 mcu's would work much better.