Ray Jefferson battery charger

Puzzle time...we have a Ray Jefferson model 155 (15 Amp) 3 output battery charger. I can't find more info online beside the limited info of the pamphlet/manual. When I hook up a battery to pos.terminal #1 and ground, the red light shines, regardless of whether the charger is plugged into AC or not. The manual says the light should come on when plugged into AC. No mention of battery connection/red light. When I connect a battery to either #2 or #3 pos. terminals and ground the light does not shine. The unit seems to function ok, but the light is capable of gradually draining the battery, unless shore power is connected and the unit is plugged in (no on/off switch). The manual does show to start with terminal #1 for the first battery and adding #2 then #3 as needed, but I don't know if this is a needed procedure or just "logical". Any ideas? Peter "Bribon" Cal 39 and non-Cal "Felicia" Ontario 32