I did monitor the batteries on a regular basis, but rather than install an expensive monitoring system, relied upon good old fashioned voltmeters and ammeters, together with a Sterling Advanced Battery Regulator. I had a battery charger on board, but cannot remember ever using it on my batteries. We tended to move every day which ensured that the batteries were always being re-charged.. The US batteries we had on the boat were desisigned to power golf buggies, small fork lift trucks etc and would tolerate being heavily discharged, without any damage occuring.