Uhhh what about the battery ratings? I think they would matter somewhat.
The testing standard for an automotive cranking battery is a load of 1/2 the cold cranking amp rating for 15 seconds, and a voltage reading taken while the load is still on. 6 volt batteries should be able to maintain a minimum of 4.5 volts, and a 12 volt needs to maintain at least 9.6 volts. Deep cycle batteries like those used in forklifts, power wheelchairs, or for trolling motors won't be able to deliver that much surge current, but they can be safely discharged down to 75% of their capacity. Starting batteries don't work well if they're discharged more than 25% routinely.
Jerry
