Al, size will dictate what you can use in there. From my experience, the small ATV lead acid batteries don't last long with a strong charger. The battery maintainer might work OK with them. The reason I suggested using a cordless drill battery was because you would already have the batteries and the charger and wouldn't need to invest in a proprietary battery for something that will only get ran once in a while. Some batteries are easy to use alligator clips on and some aren't. If you're up around 18v a resistor would be good but 6-12 really shouldn't hurt the coil. The model T mag was unregulated and could vary from 4-20+v depending on engine speed so the coils were built to take it.