# 54 cells of 50 v each on

Hi guys

Im doing a project that I need to read 54 inputs ( 4racks of 14 batteries, each one of 50 v), Im thinking of using voltage divider and then connect them to a optocupler and then to a multiplexer. I also need to save the data in a sd card as a csv file. Can you tell me if it is the right call of components?

Thanks

It sounds unlikely, exactly how are these batteries wired up?

You canâ€™t get a linear signal through an opto isolator without using op amps and a dual output isolator.

Measuring cells in seriese anbe doe with a flying capacitor circuit and relays.

Hmm you have 4 rows of 14 batteries each with each battery being 50v for a total of 700volts.
Or is each row of 14 batteries equal 50 volts.

Either way you can not just measure across each battery as you will have multiple earths and posatives comming togeather through your electronics.
You will have to measure in one of three ways.

1. Starting with the earth you run one wire from between each battery and measure each wire with respect to ground. Placing a meter on all the wires and subtracting one voltage from the other.

2. Same as the first but with only one volt meter switched between the wires.

3. Individual volt meters across each battery and each electricaly isolated.

Perhaps you could share more info on this installation and what it does?

Daz

14 cells with a total of about 50volt suggests a 14S LiPo stack.

You must already have a BMS (battery management system) in place to charge/equalise them. Some of them already have some sort of cell voltage measuring output. Like this one, with bluetooth out.

There are special (expensive/rare) chips available for cell/stack measurements. A DIY solution could be a bunch of relays and 'flying caps', driven by TPIC shift registers.

A DPDT connects a small capacitor to a cell, most of the time. And disconnects the whole cap from the cell, to connect it to the A/D for a fraction of a second. The cap is returned to the cell after it's voltage has been measured. This could take less than 20ms per cell when small relays are used. https://forum.arduino.cc/index.php?topic=396635.0 Leo..