Recently bought a crawdad that came with trolling motor & battery. I bought a fully automatic charger.

The battery won't fully charge & charger says to have battery serviced. How or where can I do that?

Should I even bother? It looks new, I'd say its about a year old, should I plan on buying a new battery in spring?

Sounds like the battery was not charged at the end of each fishing trip and allowed to sit discharged until they got ready to go again, then threw it on a charger the night before.  A very common practice that totally destroys a battery.

I would just get me a new battery when you're ready to start fishing again.   Just be sure this one is charged as soon as you get home from fishing and charged every four to six weeks when not being used.  It will give you several years of good service if you do.

Is it worth keeping the battery as spare or back up?

You can take it to an auto parts store and get it load tested.  You can also check the specific gravity of the cells with a hydrometer.  They should be 12.7 volts when fully charged.

If either of those things show bad then trade it in for the core charge because it won't be worth keeping.

Any Wal-Mart with an auto department can load test the battery. I have used their marine  deep cycle batteries with good success. They might not last as long as some others but my experience over time the longer lasting higher durability batteries and the Wal-Mart's cost the same per year. Be sure to charge after each use and then the night before you go just to top it off.

It seems that I have read that they should be about 13.2 v when fully charged. I wouldn't keep it as a spare and you will be charged if you don't have a battery to leave with them.

Most good, deep cycle batteries will have approx 12.8 VDC at full charge, after sitting 24 hours.   The low side it 12.6VDC.  Anything lower than this and the battery is getting ready for the recycle center.

I would take it to a place that sells that namebrand.

If it is only one year old, you might get a replacement.

It may be worth the trip.

Last week I made one more attempt to charge this battery. Put the charge on lowest setting. Next morning was on maintenance mode buy the end of the day was fully charged and was reading 12.7 volts?

I think I'll hang onto it. But, will buy new battery in spring .