LIPO Battery Cell Monitor

Development Boards Arduino
1

Hi and thank you to all for an informative forum.

I am unsure if this project is for the Arduino Pro Mini 328.

4 inputs: each monitoring cell voltage of a 4C LIPO battery (about 2.8V to 4.8V).

1 output: Analogue voltage showing the lowest input voltage. This output voltage is fed into another arduino (this is already up and running).

I have 12v regulated for power.

Why? I operate a Scarab Multicopter with OSD (on screen display). The OSD currently shows the main battery total voltage ie: 14.8V.

When it goes below 13.8 volts I have to land.

A much better way is to monitor the lowest cell voltage of the main battery ie: if any cell approaches 3.0V land immediately.

To whoever can knock this up will have an immediate market.

2

Maybe if you ‘back engineer’ one of the small inexpensive battery monitors or a good charger you could learn how to do this.

The key is to measure the difference Voltage of each cell without the measuring circuit referencing the common or negative (ground) lead of the battery.

So look into Differential op-amp and instrument amp circuits.

As to knowing when the LiPo is almost depleted and needing to land, I have found that monitoring the total LiPo pack Voltage is good enough if the battery is well cared for which means always do a Balance charge and keep the charge rate to about 2C.

This has been working fine on my multirotors for batteries that have in excess of 100 cycles.

After landing the cells are still matched pretty well.

3

waltr:
The key is to measure the difference Voltage of each cell without the measuring circuit referencing the common or negative (ground) lead of the battery.

So look into Differential op-amp and instrument amp circuits.

Assuming there's a tab for each cell (needed to balance the charging), why can't a single ADC measure the 4 stacks (@ each tab) wrt ground and compute the individual cell voltages ? You'd need some (differing) voltage dividers for each stack to reduce the range to that of the ADC but it should work. The true resolution of the top cell measurement would be 2 bits less than that of the ADC, how much is needed ?