I set up measurement in two ways. First the above, where the VA Tester is inline with the load and then inline with the battery. This is where I realized a use for the ability of the INA219B sensor to measure negative current. I can now see when the solar charger is draining or charging the battery and at what rate. Pretty cool, eh?
I used an Arduino Leonardo as a load with a blink sketch and as a 5V regulator for the backpack. I also modified the blink sketch to blink rapidly ten times on boot so I could tell if power was being interrupted.
I wanted to see how the charging rate changes throughout the day without sitting there watching or having my laptop connected for logging. So this was a perfect opportunity to put the USB Tester Bluetooth backpack to use.
Here are some screenshots of monitoring the battery load throughout the afternoon. A few times I had to move the panel so that it wasn't getting shade on the corner, as evident in one of the screenshots.
Finally the last screenshot I modified the USB Tester app to handle negative current. This will need some work before I add it to the released version. May need a firmware tweak as well since the min current after going negative is always 0.00V which doesn't seem right to me.
I am happen with the outcome of this test and definitely will expand upon it. Time for some EagleCAD work!