Battery bank during extended absence.

colonel4bin

I am going to be away from my homestead for long periods of time, up to 6 months. 

The house will be for sale during this time and the realtors would like there to be power available for showings. 
Basically just lights for a few minutes here and there. 

Is there a way to keep the battery minimally charged without boiling so much that the electrolyte will need topped off over a period of many months?

Like a trickle charge or something?

Specs:
48V 500 aH Nickel Iron Battery. 
Charged using 2 - Midnite Solar Classic 150’s