There's a good reason NOT to run it off your battery. You lose 35W draw while you are trying to estart a dead motor.
As soon as you trace out that hot lead to your lighting coil, you will have gained any troubleshooting insight needed in the future. That's the way to go.
Heb Dduw, heb ddim; Duw a digon
I'm that gun-totin', farm-raised, evangelical, pro-environment, OHV ridin'/drivin', Southern civil rights pro-labor Liberal yo' momma told you couldn't possibly exist.