# Measuring two DC power sources (Solar Panel + Battery)

Hi, I am trying to measure two sources of power, a solar panel and a battery.
The problem is that logically the battery is charged by a charge controller from the solar panel and therefore connected by some electrical circuit.
When I now just have two voltage dividers on a breadboard and ground both times on the Arduino, I create another connection between these two circuits, resulting in a very high current flow (up to cables melting and sparking).

Is there any easy way to solve this? Other than using two Arduinos? Jonathan

Is there any easy way to solve this?

Diodes?

Hi, Can you show us the diagram of how this is all connected?? Can you measure DC voltages with a Multimeter etc, at all thge circuit points?? Need more Info...

…some electrical circuit.
When I now just have two voltage dividers on a breadboard and ground both times on the Arduino, I create another connection between these two circuits, resulting in a very high current flow (up to cables melting and sparking).

There are definitely “some problems” with the “some electrical circuit”. Once you have those “some problems” fixed, you will be ok.

jofu:
The problem is that logically the battery is charged by a charge controller from the solar panel and therefore connected by some electrical circuit.

You need to understand that circuit.

If the solar panel and battery have a common earth, it would be possible to connect a voltage divider to each one and measure the voltage at the Arduino. Since this caused sparks and melted wires, presumably either they don't have a common earth or you messed up the wiring of the voltage dividers.

Just out of curiosity, are you expecting the two voltage measurements to tell you anything useful about what's happening? Have you tried measuring these voltages directly before implementing the Arduino-based monitoring solution?

Thanks for all the helpful replies I attached my electrical circuit for dividing the two voltages.
I thought about using a Diode. Where would I put it in the circuit?

About the electrical circuit in the charge controller I will have to look in the documentation but I assume that it is not totally trivial Yes I assume they do not have a common earth, I measured before with a multimeter as well and I have different Voltages, depending on the charge state on the battery.

Thanks again!

jofu:
Yes I assume they do not have a common earth,

Perhaps so, but don't assume - find out!

Your circuit below connect the two earths together, so if they are at different potentials this could cause very high current and potentially damage things. You need to know the design of the circuit you're connecting in to before you can safely connect in to it.