Need advice! While dry camping in North Michigan, the furnace fan died in the middle of the night! Tried to start the generator, no go. Started the engine and got generator running. I think I have to replace the coach battery (80min Reserve Capacity, and older). I can find a replacement that is rated at 190 minutes, but I wonder if I should put in two 190?s in series. Will I gain reserve time or just be spending money?