When to replace troller battery?

[MASTER Brian]

I know this sounds kind of obvious, but I have two batteries dedicated for my trolling motor. Not thinking my charger was working, I took one of the batteries in to get it tested and it came back as Good and fully charged. Plan to take the other in for a test as soon as I find the time, just didn't have both handy at time.

I believe the battery that tested Good was manufactured in either late 2003 or early 2004. The one I haven't tested yet was purchased in 2003. Both are 6yr or 72mo batteries.

Normally, I'd wait until one started failing or noticably not holding a charge, but I have a fishing trip planned at the end of April for an entire week and I'm worried if they'll hold up ok. I don't do tons of fishing as most of my time at the lake is spent with the family and my very young kids, so I really don't have tons of time behind the trolling motor....

The good one is a 27 series walmart battery, the other is a 29 series, I'm also curious how that affects operation of the troller. I'm told they should be same size, etc...

 

[Silvertip]

Re: When to replace troller battery?

Are they used in series to power a 24 volt motor or in parallel for a 12 volt motor. If they are in parallel it won't matter. If in series then they should be same capacity. As for when it's time for replacement, the answer is simple, 1) when you feel the time is right, 2) when the battery won't hold a charge, or 3) when a load test shows it is weak or failing.

 

[MASTER Brian]

Re: When to replace troller battery?

I suppose they are in series, but the connection is done at the trolling motor, because it is capable of running in 12v or 24v mode. Will it hurt the trolling motor electrics having different, or is it just harder on the batteries?

When I replace, I plan on going with identical batteries, it's just that these are what I had when I bought the boat and didn't know any better.

Sounds like maybe I should at least buy one with plans to buy another soon, even if they both test out good. At least I'd have a backup on hand if they both drained while I'm gone. I'd rather spend the money on a three bank on board charger 1st.....

 

[Silvertip]

Re: When to replace troller battery?

Since you have a 12/24 system the batteries are capable of operating in both series and parallel mode but not at the same time obviously. In 24 volt mode they will be series so run time will not be the same as it would be if you had two identical batteries. In 12 volt mode it's difficult to predict the outcome but two batteries of differing capacities in parallel will tend to equalize to the smaller of the two.