Charge Controller(MPPT) Monitoring

You can do some per solar panel string monitoring power meters pretty cheaply ($10 per string--You could even do per module monitoring if you really wanted):

https://www.ebay.com/bhp/ammeter-shunt?rmvSB=true

Do you just need to read the meters, or do you want computer monitoring? Multi-channel logging system (0-100 volts to measure panel voltage, 0-100 mVolts to measure shunt voltage, and floating inputs if you do series panel connections--no common ground).

-Bill

Here is one place to start (I know nothing about product or website):

https://www.dataq.com/data-logger/voltage/

But those do not seem to have "isolated" analog inputs--So you would (probably) not be able to put 4 panels in series and log the information for each panel with the one A2D controller.

Note, if you are doing >10 volt measurements (for example), then you can use a precision voltage divider (two resistors in series, use the midpoint to read voltage to local signal ground) to drop 30-50 volts to 10 volts max (i.e., a 5 or 10:1 divider).

I cannot quickly find a multi-channel voltage data logger with isolated analog inputs (higher isolation voltages).

It has been too many years since I have even needed to working with loggers--So I really do not know today's market. Sorry I cannot help more.

-Bill