I ran a single battery three winters straight in southern Ohio. I kept it plugged in when it got cold. Grid heater was MIA and I don't plan on one once this CR gets settled in its new home.
I ran a similar setup. Ditch the battery, you can run through 2 cycles of the grid heater with a single yellow top optima at 35F and still have power to fire it.
:hehe:Ran up to Pasco and grabbed one of their Deka Precision Built batteries. Fricken things got a rating of 1110 cold cranking amps at 32 degrees and 925 at 0. I think it should work lol. Was only $100 with me not dropping off my battery.