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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?

wiring

The INA226 PCB that I am using:

INA226 PCB

Its schematics:

INA226 Schematics

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  • \$\begingroup\$ Almost, I don't see any correct thing in that schematics. Attach a schematics in that .rar file, I won't download it. Describe what equipment you have, saying "RPi turns on even if the load is disabled from the charge regulator" means nothing, since we don't know. \$\endgroup\$ Aug 31, 2021 at 12:20
  • \$\begingroup\$ Sorry, now is clearer. I bought prebuilt INA226 PCBs from that Aliexpress link, in the .rar there is the schematic of that PCBs \$\endgroup\$ Aug 31, 2021 at 13:51

2 Answers 2

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enter image description here enter image description here

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:

schematic

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.

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  • \$\begingroup\$ Dear @Marko thank you for your answer but the shunt is already included in the PCB it.aliexpress.com/item/1005002381452716.html it's a R002 how can use that PCBs and avoiding the bypass of the charge regulator? Sorry for the question, I am not the electronic field \$\endgroup\$ Aug 31, 2021 at 13:37
  • \$\begingroup\$ @gabrielepmattia See the edited answer, to be able to use your setup you have to change the solar charger with a common negative type, you may not use a common positive type as you have it. \$\endgroup\$ Aug 31, 2021 at 15:05
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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.

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  • \$\begingroup\$ Dear @Kartman thanks for your response, what do you suggest for sensing the voltage and the current in this setting? \$\endgroup\$ Sep 6, 2021 at 16:30

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