Dead battery on 24V trolling motor.

The last two times I've been out fishing I've not had enough juice to finish my trip. Last time out I couldn't put the trolling motor on the highest speed or the motor would shut off. I could run it at about 7. So I came home and charged the batteries for a few days. Then I went out today and I ran it on 10 for a bit and it shut off again. I was only able to run the motor at about 5. So I checked one battery with my tester and it was fully charged. Then I checked the other battery and it had no charge. But the motor still worked. Will a 24v trolling motor run with only 1 battery? 

I have the batteries charging now but sounds like I need one new battery.

Can I just buy one battery or would it be better to buy batteries at the same time? They are not cheap. 

I would but an optima battery but they don't have as long a run time as other marine batteries I've looked at. 

Wing nuts are best when thrown into the spare parts box.

 When the voltage drops on your batteries, they have to work harder to do what the trolling motor is asking for. This causes heat and the breaker pops. Fresh batteries and clean connections will run cooler. If there are wing nuts on the batteries, replace them with stainless hex nuts. You cannot tighten wing nuts with your fingers, as tight as a hex nut and a wrench. A loose connection will create multiple issues over time.

 To get the best performance from your trolling motor, batteries of the same size and age is vital. It will run on 12 volts. Your outboard will run with a spark plug wire removed. Just not very well.

BigMusky your explanation sort of makes sense, but I have never heard that before either.

I inadvertently cross charged one of my batteries. What are the chances it will come back to full capacity? I have continued to recharge and use it and it seems to be doing fine.

I have an Optima D34M on my old boat that is still going strong. I think it's at about 15 years. I don't remember ever having a different battery on that boat. 

jbird

Break

Out

Another

Thousand

hahaha...boat ownership will cost you... getting 'matching' batteries is a fairly common knowledge thing among experienced boat owners... likely that your seller was unaware of that... understand how you feel, but it's not a bad investment to get the new batteries...taken care of, they should last you years

Glad you saw it!

I saw it!  Don't know why the previous owner would run different batteries together. I bought the boat this way. I'm not happy I have to get new batteries after only having the boat for 4 months. 

I am copying and pasting Tim Zwieg's post in three different formats just in case you didn't see it.  

"As stated, gotta run same size and age of batteries."

"As stated, gotta run same size and age of batteries."

"As stated, gotta run same size and age of batteries."

As stated, gotta run same size and age of batteries.

That would NOT be wise,  The larger battery will discharge less and then when that happens the large battery will then start equalizing by charging the small one.

Well I looked closer at the batteries.  Both are deep cycle. But the Interstate is a SRM-27 (160 RC) and the dead Napa battery is 8231 group 31 (210 RC). Will be replacing the Napa with same interstate battery. 

What would using a group 31 and a group 27 battery together do to anything?

poptop is right you need to load test the batteries.  As you stated in your original post, works fine at low speeds.  Its when you try to do a maximum draw is when it fails.  The tester will register "full" at rest, but will be different at a heavy draw.

Yes it could show fully charged. You need to have it load tested to see if it is good or bad.