Series or parallel?

Hi
I am asking on behalf of a friend.
Here is his video asking.
Any help would be much appreciated

Thank you

On a model that size (33% did I hear that correctly?) the batteries would be run through some kind of backer, or redundancy system. That is why there are two switches. The common ones are powerboxes, but there are others. Basically each battery is fed into the unit, and it supplies the receiver with power from whichever battery is best, switching to the other if necessary (i.e. if a battery or switch fails). They are a little bit more complicated than that, but that is the general idea.

Andy