Not to be argumentative, how is the busnut going to get the blowers to come on to test the batteries?
And how does the busnut isolate the bad battery from its partner using the coach's own loads?
The cheap tester will quickly indicate a strong or weak battery, without any further work than attaching the clamps? We're after a go,no go answer for this diagnosis.
There is way too much time and money spent unnecessarily on battery and charging systems, when there are adequate economical tools available to get immediate answers for diagnosis?
Infrared heat gun, cheap battery load tester and a decent multi-meter. With all the electrical issues a busnut faces, and the various skill sets on the Board ranging from engineer to nothing, we can help a busnut who knows little, but has those tools so we can direct their diagnosis?
Some of us are good at electrons, many are not.
Happy coaching
Buswarrior