I have several batteries that are connected in both series and Parallel. Mostly I have a bunch of 12V batteries in Parallel. But also I have some 6V batteries connected in Series and THEN connected to the 12V circuit in Parallel. Now, I'd like to monitor the status of each battery by displaying all batteries on a computer screen.
Right now, I only use one meter and whenever I see a fluctuation in the voltage supply, I have to go to each battery disconnect it and check it and then reconnect it until I find the dead battery. This is really a chore and a half!

Is there a way to keep the batteries connected AND be able to check individual batteries?
My other option is to "Run a Diagnostics" Star Trek Style and make a bunch of switches to disconnect, check the battery and go on to the next one. That might get a bit costly as I would have to buy lots of switches, wires and whatever else.

 

You can check batteries connected in parallel by measuring the current in each battery, and comparing it to the average.

 

You can check batteries connected in parallel by measuring the current in each battery, and comparing it to the average.

Do you have in mind a practical way to do that?

 

Another way is to use a differential Amp.

R1,R3 as well as R2,R4 form a front end voltage divider in this case aprox. 10:1 ratio. You just want to make sure that your MAXimium voltage you are measuring through the divider does not exceed the operating voltage of your Op-Amp.
R5,R6,R7, and R8 setup the IC1A Op-Amp as a differential amplifier.
R9, R10, and R11(trim pot) setup the IC1B last stage Op-Amp as a voltage follower with a gain of aprox 10x to compensate for the front end voltage divider. Once R11 is set you should not have to re-adjust it.

Note:
- The POS and NEG can be at any reference point in the circuit.

- The operating voltage of the Op-Amp should be slightly higher than the input differential voltage you are measuring.

- If you wish to run the Op-Amp's at a lower voltage, you can omit the last Op-Amp stage and measure the output at pin 1 of the first Op-Amp, which for this example would be 1/10th of the actual voltage, and compensate the reading in software.

 

Do you have in mind a practical way to do that?

One way is to use a low value shunt resistor in series with each battery, and make a differential measurement for the current.
More complex would be a Hall-effect current-sensor in series with each battery.

 

One way is to use a low value shunt resistor in series with each battery, and make a differential measurement for the current.
More complex would be a Hall-effect current-sensor in series with each battery.

Sure, I was thinking without redesigning the battery interconnection. But I see he did not rule that out.

 

Mostly I have a bunch of 12V batteries in Parallel.

How many is a "bunch" and what's the maximum average individual battery current?

 

Do you have in mind a practical way to do that?

Shunts or Hall-effect sensors.
Shunts are better if you need to compare current on float charge, because of the lack of offset voltage.
https://www.micro-transformer.com/Hall-Current-Sensor-pl3337725.html