Bad Charger Plug?

My onboard charger is showing "check connection" for the main battery. The two 12v batteries, trolling motor, are charging. When I removed all the leads from the main battery, the charger still showed "check connection". I then inspected the plug that I plug the extension cord into and noticed a blacking of one of the prongs. I then tried a brand new extension cord just see if the cord had gone bad. Same message on charger. Do I need a new charger even if the other batteries are charging? The main battery is just a month old.

Ideas?

I would try it on another one of the batteries and see what happens, it may just need to have the connections cleaned if it is still charging, put a volt meter to it if possible.

Okay, thanks.

I'm a little red-faced as I type this but maybe my confession will be helpful to others at some point.

I decided to attack the problem head-on this afternoon by first removing all the leads to the main battery and thoroughly cleaning them with a wire brush. Then I cleaned the posts. I then attached them and plugged in the charger. Same problem "Check connection". So I took them all off again and checked the charge in the battery. It came back at about 65% charge. I then checked the other two batteries and they were both fully charged.

I then pulled the battery out and inspected all the lines carefully then checked the breakers. All good. I sat back and thought it over. What could be the problem if the two 12v were getting a charge but the main wasn't? As I sat there I stared off into the distance and I swear I heard my dad say "Son, red is positive, black is negative". Huh? I knew that, Dad. But the thought persisted until I checked the bundles of wires for each post. It was then I realized my mistake. When I installed the new main last month I put both the positive and negative wires from the charger on the negative post of the main battery. DOH!

After sorting all that out, I plugged in the charger and it was working. I whispered a thanks to Dad and then said another prayer to the Lord for letting Dad get into my head.

Sometimes it takes an angel to set us straight.

Owning a boat is soooooo much fun. Thanks for sharing the truth.

Don't worry you may be one of the few to admit to it but you are not the first happens to the best

Wowsers, I wonder if that does any damage or is the charger smart enough to not turn that bank on?

The one bank did not charge since I had both leads on the negative post.

That's OK. About a month ago I was getting ready to go fishing with a buddy on a lake near my house. I had not used my boat for at least a month. I turned on the power and nothing lit up. Now I'm concerned. I checked the battery leads, checked the charger all lights were green. I was thinking I must have a big problem here. I was just about to call my buddy and tell him he was going to have bring his boat if he wanted to go fishing.

Took one last look in the battery compartment and suddenly it dawned on me the main 50 amp power switch was off. This new to me boat has a Power Pole and the previous owner had told me to turn off the main power to avoid having the starting battery drained or the Power Pole deploy on its own. I forgot I even had it. Flipped it on and everything worked like a charm.

Good job Dad!