My trolling motor battery is about 2 years old. Voltage tests good and it holds a charge over time fairly well but the motor just doesnt have any punch. On full charge the motor runs like I’ve been running the motor all day. Is there a good way to load test the battery without a load tester? I put the motor head in a tub of water recently, put the volt meter on the battery and cranked it wide open. The voltage dropped from 12.5 to around 10.5-11 volts which I didn’t think was too bad but it drags when I’m on the water. Any way to know for sure that it’s a bad battery? And second question is there anything going on with the motor that could be the issue?
You can take it to most auto part places and they will load test for free , but… Ive taken batteries in that were bad but load tested good. I would test it in the water with a battery ( does not have to be deep cycle ) that I know is good, from your vehicle , starting battery etc. and see if the motor acts right. If the motor is good and you have a charger that has a "start" function on it, charge the battery for a minute or so at high amperage. Battery plates develop a " film " on them over time and will prevent them from fully charging. Ive revived a few doing this and it may help.
You should probably cover the battery with a towel or something and not stand to close in case there is a short somewhere in it !
Also, after trying the above, try pulling off the prop. Look to see if anything has wrapped around the shaft between the motor and prop. This happened to us once (someones old fishing line) while fishing. A two year old motor shouldn’t be having a problem yet.
We have an old Johnson 12/24 that was fished hard for years, almost daily in the fall. It didn’t develop any problems until it was atleast ten years old. At which time I had it rebuilt.
even if the battery is good, and the motor is good, you could easily have an issue with corrosion in the battery cables.
That`s true about corrosion inside the cable and did not think of that. If some of the strands have broken, it would cause a voltage drop. I believe most of those circuits are either # 10 or # 8 depending on the length. For those interested , the formula is… 24 x the length of the cable x the amperage divided by the wire size in circular mills. For most applications the result should be less than 5 % of the voltage. In this application it could be more than 5% but will run at a lower efficiency. If you are planning to run a circuit to your dock, shed , backyard etc. send me the info and I will tell you what size wire to run.