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5 Reasons Your John Deere Mower Battery Keeps Dying

It’s frustrating to find your battery dead every time you go to cut the lawn. Having to wait on the battery to charge will just take more time out of your already busy schedule.

A John Deere lawn mower battery keeps dying when the battery cables are loose or corroded; the terminals are corroded; the charging system failed; the ignition key was left in the on position, or the battery is bad.

Take caution when working with the battery and electrical system. Wear gear to protect your skin and eyes. Follow all safety precautions outlined in the John Deere operator’s manual.

John Deere battery keeps dying

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

John Deere Lawn Mower Battery Keeps Draining

Loose Cables

The first things to check if you are experiencing a battery that just keeps dying are the cables to the batteries and other components on your John Deere.

Follow the red cable (positive cable) down from the battery to the solenoid. Then continue to follow the cable down to the starter. Make sure all cables are secure and make a good connection.

Corroded Mower Battery Connections

Next, check the connections for signs of corrosion. Corroded connections may have developed a white or green substance. Corrosion can cause your battery to have a weak charge and keep dying.

When you find corrosion on a component, you will need to remove the component and clean it.

BEFORE YOU DO THIS, disconnect the battery cable:

Disconnect the battery cable by removing the negative cable from the battery to break the electric circuit.

If you don’t break the circuit and accidentally hit the frame or other metal with your wrench while removing the battery, the battery may arc the wrench and throw sparks which could potentially blow up the battery.

Because of this, you need to always wear safety glasses and gear to protect your skin when working with your battery. Once the negative cable is removed you can safely remove the positive cable (red) with no worries.

Note: A good way to remember which cable to remove first is to remember the positive cable is the last one off and the first one on.

With the cables removed from the battery, you can take off the rest of the cables that may need to be cleaned or replaced. Cables and connections can be cleaned with a baking soda and water solution.

Mix 4 cups of water with about six rounded tablespoons of baking soda to make a paste. Spread this paste on any corrosion you find. The paste will begin to foam while it cleans the cables.

This can get pretty messy so you may want to rinse the solution off of the cables outdoors. Rinse the areas with the baking soda paste with water.

A wire brush can be used to speed things up. Another solution that works to remove corrosion is cola soda.

Faulty Lawn Mower Charging System

Once you have confirmed the cables are in good condition and securely attached, looked at the charging system.

Now that you have your cables taken care of, look into the charging system.

Test the Charging System:

  • Use a volt-ohms meter to test the charging system.
  • Turn on the meter to make sure it is registered to read 12 volts.
  • Touch the leads to the battery with the engine off. The red lead must touch the positive (+) terminal and the black lead must touch the negative (-) terminal.
    This is called reading battery voltage. The meter should read between 12.4 volts and 12.8 volts. Some batteries will read higher depending on the rate of charge and the condition of the battery.
  • Write down the number registered on the volt-ohms meter.
  • Set the parking brake and start the engine.
  • Touch the leads to the battery with red on positive (+) and black on negative (-).
  • Run your mower at about 3/4 throttle and check the meter reading. This reading should register between 13.2 volts to 13.9 volts or higher.
    When this reading is higher than the initial reading taken while the engine is off then your alternator is charging the battery.

If the reading from the last test doesn’t change from the reading of the first test then you have an issue with your charging system. The cause may be a bad regulator or a bad stator/alternator.

You will have to perform additional tests or take your lawn mower to a repair shop to determine what part has failed. Some systems are 15 amp while others are 20 amp. The size depends on the manufacturer and engine specifications.

I recommend having a professional mechanic help identify the root cause of a charging system failure. You can find one at your closest John Deere servicing dealer.

You may have an experienced local mechanic that can also troubleshoot and repair the charging system.

There are many expensive engine parts that can be at fault. Throwing parts at a problem and hoping to fix it can get costly.

If your cables are not dirty, you can perform the test above on your battery using a volt-ohms meter at any time. Performing this test may also identify a bad connection as well.

Lawn Mower Ignition Key is Left in the On Position

You may have accidentally left the ignition switch in the on position after you finished mowing.

This won’t affect the battery much unless you have an oil light on the dash or you leave a 12-volt accessory cord plugged into a mower with an accessory port.

If you find the battery dead the next time you go to use your mower because you left the key on, you will need to charge the battery.

Follow one of the methods below to charge a John Deere lawn mower battery with a battery charger.

The red cable attaches to the positive (+) terminal and the black cable is attached to the negative (-) terminal.

Charge a John Deere Lawn Mower Battery – Method One:

  • Disconnect the battery cables from the battery. Remember: Positive cable (Red +) is the last one off and the first one on. Now, if the battery has removable caps check the water level.

    If the plates inside the battery are not covered with water you will need to add distilled water to them. Note: well water is not good for a battery. City water is a little better option, but it is best to use distilled water for your battery.
  • After checking the water level, hook the charger to the battery.
  • Check the battery voltage with your meter and see what it has in it. If the battery has 11.8 volts in it you won’t have to charge it very long.

    If it has 10.1 volts your battery is going to need to sit on a charger for a while. The lower the voltage reading, the longer your battery will need to sit on the charger.

    I like to put a very low battery on what is called a “slow bake”. Some battery chargers have different switches on them such as 6 amps, 4 amps, or 2 amps.

    Charge a very low battery on 2 or 4 amps and let it charge for about an hour. After an hour, check the reading to make sure the voltage rate is increasing. If it is, continue to charge for another hour.

Charge a John Deere Lawn Mower Battery – Method Two:

If the reading on your battery isn’t too low and you need to use your mower, place the battery on a charger up to 6 amps for about a half hour to get the battery to about 12 volts.

Once the battery reads 12 volts, remove the charger and start the lawn mower. Keep the throttle up to 3/4 to full throttle and the battery should charge while the mower is running.

Once you are done mowing, check the battery reading to make sure you are in good shape for your next mowing.

Bad Lawn Mower Battery

When the battery has been on the charger for an hour or two and will not charge above 12 volts, you have a bad battery. It must be replaced with a new one.

You can find 12-volt lawn and garden batteries at your local John Deere mower dealership, an automotive store, or most home improvement stores.

Remove the battery and bring it with you. When purchasing a new battery, most stores will charge you a battery core fee between $15 and $25 unless you provide them with your old battery.

New batteries are usually fully charged when you purchase them. However, if it has been sitting on the shelf for a long time, you may have to charge it before using it.

You can place the battery on a battery charger (using the steps above) to fully charge it before placing it in your mower or you can jump-start it.

Jump-Start a New Lawn Mower Battery

Jump-start a battery by using a good battery like the one in your car. The battery in a car is 12 volts and the battery in most mowers is 12 volts. Confirm both batteries are 12 volts before attempting to jump-start the mower.

Pull the car up next to the mower and shut off the engine.

Grab your jumper cables and hook up the red positive (+) cables first to the positive terminal on the mower and then to the positive terminal on the car battery.

Then take the black negative (-) cable and place it on the car battery’s negative terminal. Connect the black mower side cable to the frame of the mower.

Set the brake on the lawn mower and start the lawn mower. Let the mower run for a few minutes. Remove the cables and you should be good to run your lawn mower.

Don’t start the car’s engine. The car’s battery will provide enough power to start the mower. Once the mower starts, allow the mower to run for a few minutes.

Remove the cables in the opposite order you installed them. The mower’s alternator will keep the battery charged.

Once again, you can check the condition of the battery with a volt meter to see how the battery is charging.

Most Batteries Are Good for At Least 3 Years

If you are changing your battery out more often than 3 years, you may have a problem with your battery connections or battery. Most batteries will last at least three years if you properly take care of them.

Follow these tips for battery care:

  • Keep the battery cables clean.
  • The cables must be tight and the battery must be securely held down on the machine.
  • Do not allow the battery to freeze. Keep fully charged in cold weather.

Most batteries fail because of vibration so make sure your battery is sitting securely in the battery tray and isn’t bouncing around the tray while you mow.

The plates in the battery will not take much of a pounding The plates can start to break up inside deteriorating the battery.

Another reason a battery can fail is due to cold weather. A battery that isn’t fully charged can freeze and damage the battery. Read more about winter battery care to avoid damaging the lawn mower battery during storage.

Lawn Mower Battery Size

When you are looking at purchasing a new battery for a John Deere lawn mower you should consider purchasing a battery with at least 300 cold cranking amps (cca) if your deck is run with an electric clutch.

The more cold cranking amps, the stronger the battery. If you don’t have an electric clutch you can get away with using a smaller battery like 250 cca, but bigger is better.

Make sure the measurements of the battery you choose will fit in the battery holder.

Learn More About Charging a John Deere Lawn Mower Battery

Learn more about batteries, charging, and charging times with our article “Lawn Mower Battery Charging Times Explained“.

Still Having Problems with Your John Deere Lawn Mower?

As a John Deere owner, you will encounter a variety of problems over the life of the equipment. These can include problems with starting, dying while mowing, vibrating, cutting unevenly, and not moving.

To help you identify the reasons your mower is having problems, I put together a handy guide to help you troubleshoot your mower. Check out Common John Deere Lawn Mower Problems and Solutions.