Put a voltmeter to the white wire and the black wire. If you get an approximate voltage of 13V you know you have a charging lead. Not familiar with your charger but know of others that run multiple (+) charging leads to run with a common ground (black wire) . These are used to run multiple battery banks. If your batteries are connected to a "1,2,Both, Off battery switch you may set the Red wire to batt 1 and the white to batt 2 and this would ensure both batteries would receive charge irrespective of where the battery switch was set at. The way it works is that the Amp output would be divided among the two batteries depending on the state of charge of each one. Some manufacturers recommend that if you use only one battery to combine all (+) charging leads. If you only lead wires to one battery or to the battery switch then the switch would have to be in Both to charge a 2nd battery. Some say that Sea Ranger was a brand name used by West Marine for radios, chargers and other electronics manufactured by various companies. You may start with them.
