MotorGuide 24 volt power loss

[Darrenkmac]

My MotorGuide model 750 12/24 volt trolling motor is losing the 24 volt use during a day of fishing a tournament. I run the motor on 3 and on 24 volts for most of my fishing. I don't usually put much use on my motor and this problem has not always been there. My batteries are only 6 months old and I charge them fully. They are Exide bought at Academy and they are deep cycle 205 reserve minute batteries. Usually in the afternoon, the trolling motor stops working. I will then put the switch on 12 volts and continue fishing. Today I tested the motor while my boat was on the trailer and sitting in my shop. It would only work on 12 volts. I plugged in my onboard charger and after about 15 minutes I pressed down the switch on the pedal at 24 volts and it worked again. My question is, why would this motor only continue on 12 volts but not on 24 as the batteries got weaker. I am use to going all day on 24 volts and even in windy conditions. Any ideas ? I know the batteries wear down during the day, but this has not been a problem in the past. I was wondering about switch contacts or maybe the pot switch or relay. Could they be going bad and increasing resistance ? Just wondering if anyone else has had this problem so that I can move forward in the correct direction. Thanks, Darren

 

[Grandad]

I'm not familiar at all with trolling motors specifically, but what you're describing sounds like what I would expect from any motor powered by a depleted power supply. If a motor has a selector switch to choose 12 or 24 volt, it's likely wired such that the windings are placed in series for 24 volts and parallel for 12 volts. As one might expect, a motor eventually stops rotating when the voltage drops below a given level. As your batteries fully deplete, the voltage that they can supply drops from say 24 to 14 volts and hits a threshold below which it won't operate. Selecting 12 volts gives a temporary lease on life that the motor can live with for the short time it takes to drop the battery output still further. Depleting the batteries this low may not be healthy for them though. And no, the switch isn't likely bad. If this is a recent change in your motor's behavior, I'd suspect it's due to the repeated deep cycling of your batteries that are likely showing their reduced longevity.

 

[gm280]

Before getting too excited, pull the two batteries and have them load tested after a full charge. Then you can eliminate any battery issue. If you find the batteries are not work great anymore, you found your problem. However, if the batteries do test good without any issues, then you need to check/clean the wiring/connections from the batteries to the TM outlet and if that isn't a corrosion issue, it can be the motor itself. But you have to eliminate things separately to find out what's going on. JMHO

 

[Darrenkmac]

Thank you Grandad and gm280. I removed the four prong plug in and cleaned up the very small amount of corrosion that I found with contact cleaner and sandpaper. That was the only problem that I found so far. I plan to completely clean all of the terminals on my switches as well. I have considered replacing my rotary switch and the foot switch as well as the 3 way toggle. From time to time when I step on the power button, I hear the microswitch click but nothing happens. Each component ohms out good when tested but my problem is intermittent and changing these components might be a good course of action. I am an Industrial electrician and actually work in maintenance in a large AC electric motor factory. I am trained in DC as well but I posted here in hopes of getting feedback from someone else that may have encountered my problem. I am beginning to worry that my root problem may indeed be that I spent good money on poor performing batteries from Academy Sports. I realize that my trolling motor is considered "old" and that I can replace it easily and solve my problem. But, my boat is a 92 ranger in very good condition and I would like to keep it as original as possible. It stays indoors and on carpet as a display in my taxidermy shop. It is an advertisement so it seems. Thanks again and wishing all of you the best.

 

[gm280]

Thank you Grandad and gm280. I removed the four prong plug in and cleaned up the very small amount of corrosion that I found with contact cleaner and sandpaper. That was the only problem that I found so far. I plan to completely clean all of the terminals on my switches as well. I have considered replacing my rotary switch and the foot switch as well as the 3 way toggle. From time to time when I step on the power button, I hear the microswitch click but nothing happens. Each component ohms out good when tested but my problem is intermittent and changing these components might be a good course of action. I am an Industrial electrician and actually work in maintenance in a large AC electric motor factory. I am trained in DC as well but I posted here in hopes of getting feedback from someone else that may have encountered my problem. I am beginning to worry that my root problem may indeed be that I spent good money on poor performing batteries from Academy Sports. I realize that my trolling motor is considered "old" and that I can replace it easily and solve my problem. But, my boat is a 92 ranger in very good condition and I would like to keep it as original as possible. It stays indoors and on carpet as a display in my taxidermy shop. It is an advertisement so it seems. Thanks again and wishing all of you the best.

Since you do understand electricity and can read an ohms/volt/resistance meter (DVM etc.), you do have a leg up on figuring this out. TM's are basically very simple. Voltage/current goes in and gets switched through to the actual motor to make it work.If you can read continuity through the switches, chances are they are not defective. I say that because if they were the problem and being intermittent they would not read continuity near zero ohms. So if you are reading resistance, then I would replace them. But if they are reading very near zero ohms resistance, it is not the switch(S). And unless you, or someone else, rewired the TM, it is not a bad wiring issues either. Wires don't move themselves around on their own...unless it is in the X-Files show. So wire connections and battery problems or the motor itself is all there is. I am assuming this isn't a PWM variable speed TM. :noidea: