Trolling Motor putting a drain on my batteries - Chicago Illinois Fishing Forum, Information & Reports
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Old 09-11-2005, 03:17 PM   #1 (permalink)
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Default Trolling Motor putting a drain on my batteries

I just replaced my old trolling motor (bow mount, 41lb thrust, 24v) beacuse it was draining my batteries. I installed the new one (71lb thrust, 24v) and took it out today. Needless to say, I had the same problem. Within about 3 minutes at full speed, it was obvious that the motor was slowing down. I checked the battery voltage, and both batt's read about 11v each, until I turned the motor on, at which point the voltage would immediately drop to about 6v each, and steadily decline. The voltage then would recover to 10 or 11 after a few minutes of inactivity. This is exactly the same problem I was having with the old one. Im at my wits end with this trolling motor situation and Im looking for any suggestions that anyone may have. There are 4 wires coming directly from the 2 batteries to a ranger style plug (4 prong with internal jumper). Anyone ever have this experience before.........

Getting Desperate,
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Old 09-11-2005, 07:37 PM   #2 (permalink)
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first how do u charge ur batteries?
2nd how does the batteries hook up to trolling motor?
3rd are u sure ur boat is setup for 24v and not 12v trolling motor?
If ur losing voltage at the baterry its bad batteries.
I run the trojans and i recommened them. u can run allday and the next day on a good charge. just dont leave them in boat all winter without charging like i did. now they only last full day.
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Old 09-11-2005, 08:13 PM   #3 (permalink)
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Did you ever have a water loss in the battery's so the water was below the plates? or a dry cell when you added water it took more than the others?
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Old 09-12-2005, 07:57 AM   #4 (permalink)
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JD Blaze,

Not sure of your system, but I would first isolate the problem to either your trolling motor or your batteries. It is easiest to check to see if the problem is in your batteries.

Hopefully you have batteries that you can access the cells. As was suggested, check the water level and add distilled water to the cells untill 1/4" below the vent well. Also check the specific gravity by cell. You can use a very inexpensive acid checker at any auto retailer. The key point when checking the acid is that you need to compare the specific gravity across the cells. If any of the cells are different by more than 50 points (i.e. 1.280 compared to 1.230) then you have a bad cell and the battery needs to be changed. Make sure there are no bubbles on the measuring arrow. This can throw off your readings.

Once you have added water and checked the specific gravities, charge your batteries without anything else attached. Check the voltage while charging. You should be somewhere between 14.2 - 14.6 Volts on most chargers. Some will detect when the batteries are nearing full charge and back the voltage off at the end of the charge (somewhere around 13.2-13.5). If your batteries are really sulfated, you might have to charge the batteries for over 24 hours.

Once you think the batteries are fully charged, do one of two things. Either reconnect the trolling motor and run for 10 seconds or let the battery sit for a good 4 hours plus. This will get rid of any surface carge on the battery. Remember any voltage over 12.8V is surface charge. Then disconnect the trolling motor if you used this method.

Now, after the battery has cooled off and stabilized, check the specific gravities as you did before or check the open circuit voltage. A fully charged battery will have a SG reading of around 1.280 or read 12.8 volts. A battery at 25% state of charge will read around 1.225 or read around 12.25 volts.

One more thing, do this last step again a day later if you have the time. If the voltage or SG reading drop, the batteries will need to be replaced (i.e. 12.75 day one 12.4 day two).

Now at least you should be able to tell if it is a battery issue or not. If the batteries are good, then you can then work on the system wiring (trolling motor, alternator, radio, etc.).

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Old 10-21-2005, 07:12 PM   #5 (permalink)
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Take your batteries in and have them tested, sounds like a bad cell, or two.
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Old 10-21-2005, 08:57 PM   #6 (permalink)
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You've already isolated the problem. Since it's doing it with both trolling motors it's a pretty safe bet that it's NOT the trolling motor. The problem lies in either your battery or your wiring. Assuming you've tested the battery have you looked at the gauge wire you're using? If the wiring isn't beefy enough you can have power losses through the thinner gauge wires. You might want to check for some frayed wires as well. Fun, fun, fun!!!
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