For travel trailer camping trip fishing, I have an 8 foot plastic boat (Sun Dolphin or some name like that) that I can put in the truck bed. For propulsion, I have a small trolling motor and a big heavy deep cycle marine battery. I haven’t used the rig in over a year, but the battery (almost 3 years old) has been on a good trickle charger when not being used. What’s the most reliable way to determine if the battery is still good enough to use, so I don’t run out of juice on the lake? Right now I’m afraid to trust it.

Since its deep cycle and can recharge and is designed to be depleted, run the troller motor and time it until it goes dead.

I personally dont know how to measure effective mAh of charge, only voltage and wattage.

Is it too small for a backup?

Battery tester

need to do a load test to see how much of a load it can handle. Most parts stores can test it. but with that said, a 3 year old deep cycle is well beyond it's life for most I have encountered using on travel trailers / hydraulic trailers as most only carry a 1 year warranty for just that reason. I have 2 in our wake boat and usually have to replace every year and a half to two years tops.

Use a battery load tester.
Don't have one?............O'Reilly's will test it.


Three years though, it's probably getting close.
I use a group 24 deep cycle for my little bass buster. I usually get about three years from one.

Put the trolling motor in a trashcan and fill halfway with water,run the trolling motor at half speed and time it to see how long it will run.You need to run the trolling motor on a load in water to see how long the battery will last.

Battery load tester. They are relatively cheap to buy. I have a boat and a golf cart and periodically test mine. There is nothing worse than getting stranded because a battery fails..

This makes sense to me.
Surprised how short a time others are saying these batts will last but I’m certain they know more than me.

For free, i may add.

And they know more than i do about this for sure, that’s why i said i don’t really know. The load test in water makes sense.
But if there is a such thing that measures the amp hours in a battery that is the way to go for sure.

I run my deep cycles in my boat 3 yrs then change out. never have had one fail. I buy the series 13 deep cycle from Walmart just so if one does die i can get one in most any town.

I would have it tested with a load tester. Then, I would probably do a trash can test too.

When I test electrical circuits, or equipment, I try to use double elemination diagnostics.

This was my thought too.....time it under a load. Run it all the way down then recharge and do it again...

Like someone said above take a backup. We used one in a creek a lot when i was younger. We always had a paddle, took a backup battery, and traveled upstream, never had a problem.

My battery charger is also a tester. Believe it is a Diehard brand. Works great.

Time is just about up on battery, better to be safe than sorry, get a new one and enjoy your trip without headaches!

I’ll go ahead and get a new one. That seems to be the smart approach. I was leaning that way anyway, but needed trusted opinions. Thanks.

Make sure you do this in water. Your motor will overheat if you just run it out of the water.

I would just buy a new one .

That is batteries that are being used frequently. It is the cycles that kill them. Not only do you need to run trolling motor in water for load but also for cooling.

Stump that helps. So clarify for me please. I use my trolling motor maybe 2 or 3 times a year. Any guess on how long the battery should last.

........about three years is average.