# Measure voltage on 48 batteries at once using microcontroller

I am looking to design a microcontroller that can measure the voltages on 48 batteries. Some of the batteries will have floating voltages as the device is wired in a parallel string of 8 columns, with 6 batteries in each column. I would like to see if there is a way limit the amount of wires, so I don't have all these wires everywhere. I am looking for any basic information on where to begin or maybe a basic single line diagram. Thank you for the help!

• Do you have any resolution, limits specs for V, I, t \$ for each. One could use 1 IC per battery with a shared AC coupled HDX data bus. – Tony Stewart Sunnyskyguy EE75 Jun 3 '19 at 20:04
• Do you require monitoring on each battery? Or does monitoring on string suffice? what is the voltage/chemistry for the batteries? – Voltage Spike Jun 3 '19 at 20:04
• I am looking to design a microcontroller You're not designing a uC, that's work for a team of experts. You try to "Design a circuit to measure 48 batteries" and possibly that would use a uC. Also there is no need to measure the batteries all at once. Battery voltages don't change that quickly so you can measure then one after the other. It might take a second or a few seconds but for batteries, that's more than fast enough. – Bimpelrekkie Jun 3 '19 at 20:13
• Semiconductor companies such as Linear Technology have solutions precisely for this problem. Mainly they are aimed at electric vehicles. – Kevin White Jun 3 '19 at 21:19
• What voltage is each battery? How accurate does the measurement have to be? – Bruce Abbott Jun 3 '19 at 23:43

It's not easy to wire and fuse 48 sense lines to batteries.

When given a big task like this, with high numbers of anything, see if you can split the problem up into smaller bits. Both to get into terrain you might already know, and to shorten the development cycle with quicker milestones.

If you have a setup with 8 packs of 6 batteries, you can create 8 devices each capable of measuring 6 voltages. Each supplied by the pack they measure to remove complicated power supplies and noise problems.

An isolated CAN or RS-485 bus can communicate the measurements along to a master unit, or whatever you're measuring for.
Such system is easier to scale than one big board with 48 analog inputs, and perhaps already for sale or available through OSHW.

This can keep individual stack units simple, as 6 to 8 is within the common count for ADC input channels. Whilst powering it from the cells themselves eliminates the need for complicated differential or isolated measurements.
Using an isolated communication channel removes possible fault currents, if any, from flowing between units or to the master.

You could prepare the unit to be able to sense more than 6 batteries. Or add a PTC channel to measure 6 series PTC thermistors to detect overtemperature in the stack.

You might want to check out Analog Devices' portfolio of battery monitor chips. Some of them have galvanic isolation allowing you to monitor cells that are far from at ground potential.