Nothing. It isn't sensitive to battery voltage, as it is a 50 V power
supply that connects for only about 10 microseconds, 70 times per
second. It hits the battery pretty hard as the current spike is maybe
10 Amps & the sparks fly a little when it is connected up. The average
current however is only a few milliamps. Don't connect or disconnect
it under load. I wiped out a couple of the hexfets (they're not IGBTs)
getting it going. It's an interesting project. I wish Jim W had
pursued it more & offered it as a kit.

Do you have a motorcycle battery to keep up?