Hello.
I have two INA219 sensors, 18V/40W solar panel, solar charger controller and 12V lead acid battery. I want to measure the voltage / current on the battery and the same on the solar panel. I use the circuit that is attached in the attachments.

Battery measuring works nice, but solar panel voltage measuring is wrong. It shows same voltage as battery (so 12V), even if solar voltage gives for example only 5V. I think that solar charger controller somehow blocks voltage measuring, or is my circuit bad? Thank you.

Hello, I have some problem too. I found your thread and look at your schematic diagram. I just realized that the INA219 your gnd connected through the arduino wich is i assume get power from your 12V lead acid battery, because of that the measuring will measure the power of lead acid battery. So i change the INA219 GND to V- Solar Cell, and it measuring well the power and current.


Mod:Link to old Thread.
https://forum.allaboutcircuits.com/...nel-and-lead-acid-battery.163701/post-1438286

 

Start off by using a multimeter when nothing is powered up to find out whether all three negative terminals in the controller are joined together. If they are (and they probably will be) it will make the rest of the job so much easier.

 

Based on an exhaustive survey of the two charge controllers I have within reach, it's a toss-up whether the positives or negatives will be common. And they may not be truly common but have a current-sensing resistor between them. The RBL-8810/KW1210 10A/LCD/PWM/USB controller I got from ebay was positive common; the no-frills 8A controller bundled with a 25W Noma solar panel had negatives tied through an R020 resistor to sense current. So a sensor arrangement that works for one controller won't necessarily work for a different one.