Originally Posted by
MartinCaron
1- Those perko selector are for charging as well as dischaging batterys
2- Only the battery that the selector is set to. If "both" then both...
When the motor turn for a long ride put it to both so the alternator charges both battery. Note the alternator push more amps than the boat demand so when the motor turns your only charging. You should only consider "both" as a charging setup.
When the motor is off and your using the radio, ballast, heater, etc you select only one and the other become your backup start.