John,
Was one of the wires (probably the red) much thinner and used for the feed to tell the charger a battery is connected? More current Chargers use three wires to the battery connector with the small wire used only as a sensor lead and not carrying any of the charge current. This old "Total Charger" uses only two leads but has a tap inside the charger going to the PC board. I take it you don't have a schematic (not just a wiring diagram) either??

Mark