Grip Heater power draw

[farmerj]

While searching here revealed some good threads about Grip heaters, they were largely on kick start bikes and my question wasn't answered.

The stator puts out about 70W. Grip heaters use approx. 35W. I'm guessing I won't be able to run my headlight when I'm using the Grip heaters (?). That leaves 35W to charge the battery.

How many watts does it take to keep the battery charged for starting system use? I don't want to draw the battery down too far and damage the starter with low voltage. Is 35W enough?

Thanks,

Jeff