i don't think some people on this thread understand how this relay works.
its a voltage sensing bi directional relay, meaning the minute the charge voltage from the alternator/solar/grid goes above a certain voltage the banks are connected. thus if your connected to grid/generator/solar, and your charger is working, there is no way for the starter battery to go dead considering its getting charged, when the voltage drops under 13v the banks disconnect, in this case using the override switch will allow the relay to connect the banks and start the motor
realistically you should never have a dead starter battery, that said if you do, i would recommend waiting a minute or so in override before attempting the start
