Multiple INA226 PCB for solar monitoring with a Raspberry Pi

Question

For a project, I have a solar panel and a charge regulator with a 12V battery. The load is a Raspberry Pi. I want to monitor the voltages and the current flowing from the panel, the battery and to the RPi. I bought three INA226 prebuilt PCBs from AliExpress (schematics below.)

The wiring that I am using is the one in the image. The problem is that when I connect the GND of the INA226 board (U2) of the battery to the GND of the load (U3,) the RPi turns on even if the load is disabled from the charge regulator. The same happens when I connect the VCCs but a lower current is flowing to the RPi.

I tried to attach the U1, U2, U3 to the buck converter but from the bad smell I think that should not be done.

What am I missing?

The INA226 PCB that I am using:

Its schematics:

Answer 1

You do supply 5V at Vs, the I2C bus shall have pull-up resistors mounted: two of them 5V<->SCL, 5V<->SDA.

The INA226 is made for bus voltage & current monitor, so you need a shunt to measure the current, and not direct connection on panel, battery, load,...

As you may see, there are Vin, Vbus,...not the same pin names as you have in your schematics.

The smell comes from INA as you already burned them.

EDIT:

^{simulate this circuit – Schematic created using CircuitLab}

As some other user want's to suggest, is that your charger uses a common positive. When you connect minuses, you actually bypass the internal switch of the regulator.

The smell could be a PCB track overheating, since all the load current now passes through tiny track, also it answers why the load turns ON, even if it is disabled on the charger control.

Answer 2

Your solar controller is most likely switching the - inputs from the battery and solar cell in order to control the charging etc. joining the - wires via the INA229 boards bypasses all of this, so it won’t work.

You’ll need to find another method of sensing the voltage.