If you have 2 watt meters that can measure consumption over time, you can plug that into the input of an AC300 and another one of those on the output and compare the difference after a day. I only have 1.
After over a year my AC300 setup has not “bricked” after applying every firmware update.
Coincidentally, just yesterday, after a battery recalibration and charging both B300 to 100%, I decided to apply the Firmware. Other than a nervous pause halfway through, all good now.
I can’t say I noticed any difference and unfortunately it doesn’t seem to have fixed my issue with the batteries being out of sync.