Batteries not holding charge - Trolling Motor?

[gsmith3286]

Hi,

I have a MinnKota 80lb 24v TM. Both batteries are relatively new. I have an onboard charger that is kept on at all times while off the water.

The other day I was out and the batteries went dead after about 2 hours of trolling. I used to get more than a full day out them.

Pulled both batteries, charged them up to full, tested with multimeter, Batt #1was like 12.8 and Batt #2 was 12.8. Tested the connection on the plug and it read something like 24.6V which what I expected. I took it apart, cleaned it up, applied some electrical grease, and tightened everything back up.

Other than on-board charger and TM, nothing else hooked to batteries.

Any ideas? Bad battery or problem in the TM itself?

GS

 

[bruceb58]

Re: Batteries not holding charge - Trolling Motor?

How far do you discharge the batteries before you charge them up and how many times have you discharged them to date? Both of those have an impact on the life. When you take the batteries off the charger, let them sit for 30 minutes before checking the voltage...should be 12.6 if fully charged. Also, never discharge them below 12.0V which is around the 40% level.

 

[gsmith3286]

Re: Batteries not holding charge - Trolling Motor?

Thanks Bruce...I actually did a hydrometer test and both my batteries failed with most cells in the red. This is terribly frustrating as I am very anal about keeping my batteries charged full.

My batteries do not get heavy use as most of my fishing is river fishing..drifting mostly and I get out less than 50 times a year.

Is it possible that the on-board charger I have is destroying batteries? I'm beginning to wonder...

 

[bruceb58]

Re: Batteries not holding charge - Trolling Motor?

What type charger is it?

 

[John_S]

Re: Batteries not holding charge - Trolling Motor?

Is it possible that the on-board charger I have is destroying batteries? I'm beginning to wonder...

Maybe. I have seen some batteries get boiled over. This was with a non-marine/onboard charger, and believe it was related to brown-out or lost power. I don't leave the charger on more than 24hours.

 

[gsmith3286]

Re: Batteries not holding charge - Trolling Motor?

Thanks for the advice...I definately do not trust my on-board charger and I will only use it overnight and use my regular 12v charger when time permits.

My on-board is ProMariner ProSport 12 (2 banks). One bank has a tag on it that says "starter battery"...could it be possible that it charges differently than the other bank that's used for the TM???

I had two other on-board chargers in the last 4 years. The first was a Bassmaster 2 bank...I found out that it was defective after the GFI in my garage kept tripping. Fortunately, it was under warranty so they sent me ProMariner ??? - it too died within the year as evidenced by the GFI tripping again. They finally sent me this ProMariner ProSport 12.

The 2 batteries that died: one was Interstate and the other an Everstart...would that matter?? Do both batteries need to have identical
specs? I've had no luck Interstate...this about the 3rd one in 5 years... I never had luck with Everstart but I was in a jam when I bought it.

Now, I have two Die-Hards...$100 each, but.....