Trolling Motor Battery Issue

[Not Retired Yet]

The issue I am having is one of the three batteries for mytrolling motor seems to be draining faster then the other 2. Yesterday when this happened I checked thebatteries out on the lake. 1 -12.1VDC, 2 – 9.3VDC, and 3 – 12.2VDC.

I have notice this twice this year when I have had to usethe motor in the wind. I do understand that running the motor on 5-7 or 8 willdrain the batteries faster than on 2-4 power. That I understand, but this isthe second time I have run into this problem in the last 2 years. The firsttime this happened I had the battery tested and it would test ok at the store,so I did my own load test by hooking up a heater to all three batteries andtested them every hour. The batteries went down equal until the one battery droppedoff from 11 volts to 7 compared to the other batteries. I replaced the battery (theset was 1 year old) and everything worked fine all last year.

This is what I have for equipment and batteries:

• 3 – Group 31 Batteries – MCA@32 deg – 800 Amp, CCA@0 deg – 650 Amp, Min@23 Amp – 225. (matched set)
• 3 Bank Charger 10 amps per bank.
• Connections check and cleaned at the beginning of each season or at the end of the season.
• 36 volt trolling motor 2 years old.
• Factory wiring from the Trolling Motor the batteries.
• The battery that is having the issue is the battery in the middle of the three batteries. The other two batteries tie to the trolling motor (+-)
• I charge the batteries the night before I go fishing and the day I get back from fishing for a day or so. (learned my lesson in the past)
• Batteries were kept inside all winter and charged on an occasion to keep charged.

I have been checking the batteries as they charge andnoticed this battery seemed to take longer for the charger to drop down from itsinitial high charge. The other two batteries would drop off much sooner thanthe this battery. It is the same battery of the string of three that this hashappened both times.

Anybody have any ideas of a solution? Could it be thebattery charger is not working correctly and over charging the battery or couldit be just a coincident that it is a bad battey?

Sorry for the long winded ask here but I’m looking for someideas to keep me on the water all day or at least until the all the batteries sayit’s time to quit. I am confused with thisissue and do not want to just keep buying a new battery every year or so.

Thanks for the help.

[Wyo-eye]

Switch the charger leads of the battery in question to one of the better batteries and vice versa for a trip or two to see if the bank of the charger is at fault, or the battery.
A similar thing happened to me, thought it was a bad battery but was that one bank of the charger not working correctly.
A new charger fixed it.

[mikear]

Is the battery in question the same bank you changed last year? If so, I would highly suspect the charger.

Are your batteries dual purpose or true deep cycle?

Also, you might check the voltage at the motor leads where they terminate to the TM while under a load (prop in the water) if safe to do so. Make sure you don’t have excessive voltage drop. Compare that reading to the voltage at your battery terminals.

This would not explain the single bank failing, but it could potentially place more stress on the batteries.

[TomP.]

I would do as stated above change charger leads first if that shows nothing then I would charge batteries unhook everything check voltage> Let them sit for a day or so and recheck voltage if they drop below 12.5 volts that battery is bad. A load test will not always show a weak battery.

One thing I have done is run a ground from the skeg of the trolling motor to the starting battery ground, knock on wood this has cured all my interference issues.

Some have had issues with interference coming from the charger unhook your onboard charger and see what happens Humminbird has a choke you can add to clear this up if this is found to be the problem.

I would also double check all my grounds.

[Not Retired Yet]

I will try to switch the leads of the charger to another battery and see if that makes a difference for the charging the battery in question. That sounds like something I should have done anyway.


Yes, it is the same bank/battery/charger in question. The batteries are deep cycle. When i go out next time i will pull the plug out of the wall and check voltage under load (shouldn't be a big deal).

[mikear]

If it’s the same bank I’d assume you have a charger issue.

1. I would leave the charger hooked up as normal and let the batteries charge overnight.
2. Shut the charger off and wait 6-8 hours to let the “surface charge” dissipate.
3. Test your voltages on all three banks and note them.
4. Use the batteries under a load.
5. Swap the leads from the charger and repeat steps 1-3. See if the voltage measurements are the same or if the lower voltage battery is now on the questionable charger bank.

[egladding]

I would be very leary of just changing the leads around from your onboard charger. I had a 4 bank noco genius on my boat and had one of my batteries go bad. The 3 trolling motor batteries were less than 1 year old. The charger went bad and over charged one of the batteries. I got the battery replaced and used a separate charger for that bank. Two other banks went bad within a few weeks and ruined the other 2 batteries. I replaced them and bought a new onboard charger.
If that is the case with your charger then you are risking ruining another battery on your boat.

[Not Retired Yet]

Update from my trip to the lake yesterday.
1. I swapped leads from the charger two days before going and charged the batteries. Same issue with the changer to the middle battery.
2. I checked voltage at the batteries under load with the trolling motor on #6. The voltage at the batteries was 37.5 and 37.3 at the trolling motor through the plug. .2 volts drop did not seem to bad to me.
3. Ran the motor for 5 - 6 hours from 2-7 power. Checked the batteries on the water and bank 1 and 3 were 11.45 and 11.5 DCV. Bank 2 was 7.65.
4. Returned to the house and pulled the battery, pealed the sticker off of the battery to reveal the cell plugs, and checked the cells. No acid in any of the cells. Looked through the inside of the tray and battery area for any possible spillage and did not find any trace of possible acid spill. What happened to the Acid????????


With all of that I feel the charger is working correctly and I will need to replace the battery.


One thing I must note is that in looking at the batteries the date on them is not last years battery but two years ago. My how time flies when your having fun.


Thanks for the input on possible issues..

[Ozark Bob]

Originally Posted by Not Retired Yet

Update from my trip to the lake yesterday.
1. I swapped leads from the charger two days before going and charged the batteries. Same issue with the changer to the middle battery.
2. I checked voltage at the batteries under load with the trolling motor on #6. The voltage at the batteries was 37.5 and 37.3 at the trolling motor through the plug. .2 volts drop did not seem to bad to me.
3. Ran the motor for 5 - 6 hours from 2-7 power. Checked the batteries on the water and bank 1 and 3 were 11.45 and 11.5 DCV. Bank 2 was 7.65.
4. Returned to the house and pulled the battery, pealed the sticker off of the battery to reveal the cell plugs, and checked the cells. No acid in any of the cells. Looked through the inside of the tray and battery area for any possible spillage and did not find any trace of possible acid spill. What happened to the Acid????????


With all of that I feel the charger is working correctly and I will need to replace the battery.


One thing I must note is that in looking at the batteries the date on them is not last years battery but two years ago. My how time flies when your having fun.


Thanks for the input on possible issues..

With 2 year old batteries that third one will not match up well. It will not last any longer than the other 2 old ones. Convention says replace all 3. And in your case the charger too. I know it is not my money. Only my opinion. Bob

[Snowking]

I would be a little worried that the charger is malfunctioning one bank. And overcharging that battery causing the water to evaporate. You maybe would not notice it switching the leads and charging that other battery once. You may want to check the water levels in the battery you switched to.