Here’s What to Do If Your Lawn Mower Battery Is Dead

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You are ready to start cutting your grass on a beautiful day only to find out that your lawn mower will not start. Even if you can start your lawn mower, it cuts off in the middle of the job. The first thing you should do is check the battery!

What do you do if your lawn mower battery is dead? First, you want to make sure the battery is dead. 

  • Check the connections.
  • Listen for clicking sounds.
  • Try charging the battery.
  • Check the water levels.
  • Do a voltage reading with a digital multimeter. 

Once you know for sure that the battery is dead, replace it. Make sure to find out why the battery died to prevent any issues with your new battery.

There are several reasons as to why your lawn mower battery is dead or dying. Now is the time to sit and examine your lawn mower so that you can eliminate any causes that have nothing to do with your battery. This article will explain how to properly check if your battery is dead, how to eliminate the cause, and how to replace it easily. 

How to Tell if Your Lawn Mower Battery is Dead

There are a few simple ways to check if your lawn mower battery is dead. After all, sometimes lawn mower batteries aren’t the reason why the lawn mower isn’t starting. Therefore, the first thing you should do is check to see if the battery is actually dead or if another factor is inhibiting the lawn mower from starting. 

  • Check the connections. All of the vibrations put out by a lawn mower can cause things to become loose. Check the connections to ensure everything is tightened as necessary. Gently pull on the wires. If they are loose, tighten them with a wrench.
  • Listen for clicking sounds. If you hear clicking noises when you try to start the lawn mower, it can be a fairly clear sign that something is wrong with the battery, and it will need to be replaced.
  • Charge the battery. Sometimes it’s a simple issue of the battery not being charged properly or long enough. If this is suspected, connect the battery to the charger, set it for 12 volts, and wait 8 hours for the battery to be fully charged. If the battery is still not charged after 8 hours, it is time to replace the battery.
  • Check the water reservoir. This is the most straightforward fix, but an important one to keep the lawn mower running correctly. Check the water reservoir. Water should be filled to the maximum line. If not, fill the reservoir with distilled water until it reaches the maximum and try to start the lawn mower again. (Source: Northeast Battery)
  • Perform a voltage reading. Almost every riding lawn mower has a 12-volt battery. Start by switching the digital multimeter to “DC” or “A.” When setting the meter to test the battery, set the meter’s value 1-volt higher. For example, with a 12-volt lawn mower battery, set the meter for 13-volt. 
Digital multimeter

If there are any readings on the digital multimeter that are at or below 11.5-volts, then the battery will need to be replaced. Any reading that is above the battery’s voltage, for example, 12.7, means the battery does not need to be replaced yet, and there is probably another cause for the lawn mower not starting.

Causes of a Dead Battery

A lawn mower will not run with a dead battery. But what are some of the reasons why a battery would die? Here are the top 4 causes of a dead lawn mower battery:

  • Problems inside the lawn mower: The components that make a lawn mower work are sustained by the battery. Should any of these moving parts remain on after the mower is cut off, then the battery will still be continuously working and draining.
  • Corrosion of the battery: Corrosion can easily be spotted as there will be a distinct white build up on the battery or its connectors. Corrosion happens when gases are leaking through a crack in the battery and begin to spill out. The crack will make the battery do double the work.
  • Battery recharging system: To recharge a lawn mower battery, the lawn mower needs an alternator and a voltage regulator. If even one of these parts stopped working, the battery would not receive the full charge it needs to work correctly. 
  • Battery lifespan: Batteries don’t last forever; most batteries last for approximately four years. The battery may still be able to run, but it will not hold a charge like it used to.

It is essential to check the lawn mower’s battery every now and then, especially during weeks or seasons where it is not used as frequently. Consider cleaning the battery holder and the battery itself to clear corrosion. After figuring out what caused the death of the battery, it’s time to replace it with a new one.

Choosing the Best Lawn Mower Battery 

Choosing a lawn mower battery is an important decision. Review the one that is currently dead to find the best choice for the lawn mower. Pay attention to the following critical details when choosing your new battery:

  • Battery Measurements: There is nothing worse than purchasing a new battery only to have it be too big or too small for its holder. Bring the old battery to find the size that is needed quickly.
  • Voltage Size: The battery voltage that the lawn mower came with is the exact voltage that should be purchased once more. Purchasing a battery with a higher or lower voltage could disrupt the performance and power of the lawn mower.
  • Cold-Cranking Clamps (CCA): Another identical situation like the voltage size are the CCA. CCAs measure the current flowing through the battery. Look at the battery or the lawn mower’s manual to identify the actual value of CCA and avoid a CCA that is too low. 
  • Terminal Positions: Determine the side of where the battery needs to be positioned. The wires should not be too tight. The wires should be slack to ensure a constant, natural flow of power.

It is recommended to purchase an additional backup battery while purchasing the replacement. This ensures that an additional shopping trip isn’t needed any time soon. This should only be done, though, if you are planning to keep the lawn mower for an extended time, as batteries can last four years (and sometimes longer, depending on maintenance).

How to Replace a Lawn Mower Battery

Taking out an old battery of a lawn mower requires a bit of care. Always wear gloves and goggles for protection. Remember — a battery’s insides are toxic and can cause damage to the skin, so be careful. 

Here are the steps to removing and replacing the battery:

  1. No matter the type of lawn mower, there are a couple of places the battery could be. 
    1. The battery on a riding lawn mower is either under the hood or right underneath the seat of the driver. 
  2. Lift the latch to remove the seat and lift the hood to remove the battery.
  3. If corrosion is seen while removing the battery, detach the black (or ground) wire. Mix baking soda and water into a paste. Apply the paste thickly and let it sit on the terminals for 5 minutes. Remember not to let the water go into the battery. Brush off the paste with water to remove the corrosion and dry the battery with a cloth.
  4. Use a flat head screwdriver to remove any connectors that are too hard to remove by hand. After taking off the black wire, remove the red wire.
  5. Take out the battery and clean out the place where it once was. Place the new battery inside and attach the positive cable first and then the negative. 
  6. Strap down the battery, and everything is all set to do some yard work. To properly dispose of your old battery, take it to an auto parts shop or recycling facility. 

In Conclusion

Replacing a lawn mower battery is relatively simple, but you don’t want to replace the battery when it isn’t necessary. So, always take steps to make sure your battery really is dead before replacing it. After all, if something is messing up within your lawn mower, it can quickly kill the new battery you purchase.

Peter Toth

Hi! I'm Peter, the owner of BackyardGadget. Working around the house has always been a big part of my life. I've created this site to share my experience, and to help people choose the right tools for the job. Thank you for stopping by!