battery charging problem

[bmH1065]

My batterys were new this summer. Hadn't started it for a couple of months. Started right up. I took it for about a 20 mile drive. A couple days later the batterys were dead. Must of left light switch on or somthing. I disconnected batterys and put 12 volt charger on. Next day battery was fully charged. Switched charger over to second battery and charger tells me that the polarity is reversed and will not charge hooked up + to +, - to -. It souldn't be reversed should it? Don't know what I should do. Thanks.

 

[bmH1065]

Thought I had hooked up batterys wrong but they were right. Got the battery to charge . I still don't have any headlights. All of the others work. Dimmer switch doesn't change anything. I guess I will replace light switch.

 

[Stalwart]

I had this happen with some fairly new 6TL's. Someone here recommended putting a load on the one that was reversed and completely drain the battery. 12V lightbulb, small motor, anything that you can use to get the battery to 0V and then try to charge normally with a 12v battery charger. Get both batteries fully charged separately while completely disconnected from the truck and then reconnect them after charging.