With a good battery, either 6 or 12 volt, the charging system is supposed to work hard for a few minutes right after startup, then cut back to a smaller current flow to maintain the charge. What most people who don't make a living doing auto electrical work don't realize is that the charging system powers the ignition, lights, wipers, heater/AC fan, and other accessories first, and then uses its remaining amperage capacity to recharge the drain on the battery from getting started. If you've got 50 amps' worth of constant demand, with a HEI ignition, a big thumpin' sound system, dual electric cooling fans, a big air conditioner blower, power windows, and an automatic electric buttwipe, the alternator must be matched to the constant demand, plus about 25% amperage over that number to keep the battery charged.
Jerry
