1 battery or 2

I have a single conventional battery and an alternator that I switch off the field when I get to the line (takes off a tenth or two) and turn back on after crossing the traps. The car still gets weak after 5-6 passes and at the last outing it would not give me that last needed crank after we had to shut down at the waterbox due to the guy in front wrecking. If you plan to run a generator in the pits between passes to power a charger you may be OK with one but for me there will be two batteries in da fish. I drive the car around the street and like to have an alternator but not starting when you are lined up with a cool 4sp 440 6p 'Cuda sucks, especially cause I woulda beat him by 3/4 second.