Onan generator shuts down

We had a similar problem with our Bounder. It turned out to be the coach batteries. We added the necessary amount of Distilled water and the Generator ran fine. However, that was not the only issue.. it seems the Converter / Battery charger had lost its ability to detect a over charge mode... So the cycle begins The Gen., would run the charger which actually over charged the coach batteries, and boiled off the water in the batteries, causing the gen, to run hot and go into a shut down mode.. The reason I throw out this as a cause is we have our gen serviced every 4 months, with include all filters.. I was fairly confident it was not a fuel problem causing the Gen to act wacky