Battery box humming

[RosiesGuy]

A recent power surge has caused a humming noise emanating from the battery box. Unplugging the Airstream from it's power source does not stop it. The only way is to hit the battery disconnect switch for storage. Are there any thoughts why it's doing this,or process to determine why it's happening?

[SteveH]

By operating the disconnect switch as you probably know, takes all load off the batteries and the converter. This might indicate that there is an excess current draw from the batteries.

I would suggest you do some voltage tests to see if the batteries are under heavy load, and if so isolate circuits till you find the heavy load.