How to Test Trolling Motor Batteries?

how to test trolling motor batteries

Trolling motor is an electric device that’s being used in a fish boat to help it move quietly and avoid spooking the fish. This motor runs with power supplied from its own battery bank.

Trolling motor batteries aren’t like car batteries and they often need to get tested. Such batteries require a big amount of power for a long time. Many anglers complain that a trolling motor battery doesn’t last a long time. Cheap deep cycle batteries provide a less duration as trolling motor battery lifespan depends on a set of factors.

On the contrary, a good quality deep cycle battery delivers greater watt-hours per liter and watt-hours per kilogram. They maintain a higher peak capacity in each charging cycle.

Take a look at their site and read about trolling motor battery.

You can check the charge level of a trolling motor with a hydrometer or a multimeter.

Testing Trolling Motor Battery With Hydrometer:

You can test trolling motor batteries with a hydrometer. This is the most accurate way to test a battery. Aircraft lead-acid batteries are monitored with this. Measuring the density of electrolyte by measuring the specific gravity of the electrolyte is the method the test is performed with. The density of the electrolytes are as high as the concentration of sulfuric acid. The charge level depends on how high the density is.

1. Allow the thermometer to adjust the electrolyte by drawing electrolyte several times into the hydrometer. Now note the reading. If the color is brown or gray then it means your trolling motor battery is having some problem and about to die.

2. Draw a full sample of electrolyte by allowing the float to float freely.

3. Holding the hydrometer vertically, note the reading carefully. The reading should be where the electrolyte meets the scale on the float.

4. Add or subtract 0.004 points to the reading for every 10° F the electrolyte temperature is above or below 80° F.

So if the reading shows the gravity is 1.250 and the electrolyte temperature is 90° F then the original reading is 1.254. A hydrometer reading of 1.265 indicates a fully charged battery.

5. Test all the cells and note the readings. A difference between two cell readings of fifty points indicates a problem with the low reading cell.

12.60-12.74 = 85% to 100% charged

12.40-12.59 = 75% to 85% charged

12.20-12.39 = 50% to 75% charged

12.00-12.19 = 25% to 50% charged

12.00 to below = fully discharged

NOTE: Wear protective clothes as the battery contains sulfuric acid.

Do not perform the test on a newly installed battery. A battery must have to go through one charged and one discharged cycle to be eligible for this test.

Testing Trolling Motor Batteries With A Multimeter:

Multimeter is an instrument to measure electric current and voltage. This is growing popular amongst anglers nowadays to test trolling motor batteries.

  1.  First of all, note the reading of voltage capacity and temperature of the battery. Trolling motor batteries shows the reading of state of charge(soC) for different types of batteries. If you don’t charge soC will be more than three fourth which means 75 percent if it is in rest mode for two to eight hours.
  2.  Turn the fuel supply off and turn over the engine with the starter motor for fifteen seconds. Note down the lowest voltage during this time period.
  3.  Slowly connect, medium load and take the reading how much power it discharges. Load recommended two capacities are 2:5. Discharge testing of the battery is to be set with a DC ammeter. Current and voltage can be measured in every frequency.

WARNING: Deep cycle batteries are always risky to handle. If you don’t feel flexible handling it, call an expert and learn it first.

A good quality multimeter is required to have accuracy in each test.

Faulty Batteries

If your deep cycle battery is fully charged but lose the power very fast, you have a battery that has faulty cell. If one of your batteries has dropped down to 8V, you’ll notice other batteries within this bank have dropped down too. To find out the faulty battery, disconnect all the batteries and run test on all of them individually. The battery with the lowest voltage rating will be the faulty battery. You should replace the battery as soon as possible in this case.

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