Need Some Help trolling battery

About 6 months ago I had 2 new Continental Trolling Batteries put on the boat and a new Minn Kota Digital 3 Bank charger. Two weeks ago I charged batteries and noticed the warning light on battery #2 but was in a hurry and went fishing. Only fished a couple hours no problem. Charged batteries again over night before fishing a tourney Saturday. Noticed warning light again. Went on and fished Saturday and had no problem and then about 1:00 I couldn't get it to push. Loaded cup early. Got home and cleaned posts and made sure I had a good connection. Charged again and had the solid red light warning. Minn Kota told me could be one of 5 problems:

1: Battery has over 16 volts
2: Battery has under 1.5 Volts

Volt meter says 13.5 so not the problem.

3: Bad connection but I checked and cleaned what little dirt there was, so it isnt this.

4: Leads are on wrong polarity, double checked and they are not
5: There is a short. When I put the wires on the other battery it works fine.

I'm guessing the reason I lost power is that battery never got fully charged.

So do I have a bad battery? It shows the have 13.5 volts so that doesn't male sense. Any Ideas?

You really need to load test the battery. And check the battery.

Charge it for 24 hours, disconnect and let it "rest" for 24 hours, then load test it with a resistive testor. Harbor Freight sells them for around $12. If you don't let it rest, a surface charge can give you a false result.

Put a full charge on it and carry it in to a dealer. They'll load test it and replace under the warranty if needed.

Sounds like you're reading the surface charge. My guess is the battery has lost it's storage capacity. If the charger is working when the leads is swapped, it's going to be a battery issue. If you don't want to pull it to have it load tested, take it fishing again, with both batteries charged, and when you get back before putting it on the charger check the voltage. If my guess is correct, the suspect battery will be substantially more discharged than the good battery.

Your troubleshooting step 5 eliminated the charger. Pretty much confirms bad battery.

That's what I am thinking, love it when a battery only 6 months old goes bad.

Well, this was disappointing, bad battery charger. One bank is bad. Seven months old and went out. He said the others would still work so I will charge trolling batteries only until the new one arrives.

I didn't know Continental made "trolling batteries". Check and make sure they are actually deep cycle batteries and not dual purpose. Those won't last very long under repeated charging and discharging. At any rate, Continental batteries are not generally well thought of, right up there with Exide and Interstate.

As far as the charger failing, I had a bank on a Pro Mariner go out after a couple of uses. it happens.

I have never had good luck with Continental either. My dad sold Continental, Interstate and Motorcraft at his shop in the 80's, and there were some faithful followers of Continental at that time that he stocked them for, but we always recommended others. Batteries in general across the board are not what they used to be.