Had problems with my TM last year and had the batteries checked at Batteries Plus. They were fine, problem ended up being the circuit breaker. After that the trolling motor, a 2017 Minn Kota Ulterra worked fine rest of the season with the same batteries. They are Interstate deep cycles from 2014.

 

Now this year I'm having problems with the Autopilot and Spotlock not working but the TM will still work for hours without those features. Whenever I tried the features I got a set of chirps/beeps and that feature wouldn't work.

 

I charged the batteries with my other charger rather than the onboard Minn Kota charger and got the features to work again although only for about 10-15 minutes. I assumed it was the batteries. The TM continued working again without those features for hours.

 

One the batteries on the onboard charger batteries always goes to solid green (full charge) and one always flashes green. I checked the water in the batteries and one is definitely low. I can see the top of the plates by about a 1/2" inch. The water in the other battery is fine. Note: I do keep my batteries plugged into the onboard charger all year long and it is in a warm pole-barn all year long.

 

 

Can I put more distilled water in this battery and it will work or is it ruined now?

 

Short answer is maybe.  Fill it with distilled and charge again.  If it takes a charge you should be good.  Personally, I have never had good luck with Interstate's  but many have.  Also remember the batteries are 4 years old.  

A couple of things.  After connecting the charger, wait until the next day and check the voltage with the charger still on and connected and see what the maintenance voltage the charger is putting out.  My Minn Kota 330D is 13.68 volts, which is way to high for flooded cell, deep cycle batteries.  13.2VDC makes them a lot happier.  Too high of a maintenance voltage will cause the water to evaporate much faster and shortens the life of the battery.  I no longer leave mine on 24/7 until I take the notion to open it up and see if it's adjustable.

 

Second thing, the battery could just be on it's last leg.  As a battery ages, it gets hotter as it's being charged and cooks the water out a lot faster.  You may also notice a strong sulfur smell if it's getting very warm. 

 

Always add distilled water.  All that evaporates is the H2O and the acid gets stronger.  Also, only add it after the battery has been charged.  If you add a lot of water to and uncharged, cold battery, as it charges, it can make the battery overflow.

 

If the water gets below the plates, it lets the plates start deuterating and flaking apart.  This can cause the cells to short. 

here's how to check your battery(s). Charge the battery until the light turns green. Unplug the charger and use a voltmeter to check the battery. The reading should be at least 12.7 for a battery that is 100%. Some batteries will give readings up to 13.1 or so. Let the battery sit for one hour and take another reading. If the reading is the same, your battery is ok.  If the reading drops, your battery is wearing out. If the reading is below 12.5, you might think about getting a new battery. A reading of 12.5 indicates half a battery

Personally I would not charge that battery without adding just enough water to be even with the top of the plates. Charging it more can only damage it further.

I never ever leave a battery on charge once it is charged.  I run 3 very expensive Cabelas group 30 AGM batteries. I charge he batteries up. I use the boat and upon returning home recharge the batteries.  I park my boat until it is to be used again.  The batteries in my boat are on their 8th year.  I expect to need new ones but have not needed them yet. I use a Bass Pro 10 amp per bank charger designed for charging AGM batteries.