Can you Overcharge a Lawn Mower Battery? How to Avoid It

Prolonged storage of a lead acid battery makes it lose charge. Before and after the cold winter, you’ll need to charge your lawn mower battery. This is important to the battery’s lifespan and a headstart for spring mowing preparations. So, can you overcharge a lawn mower battery?

The answer is yes. It is possible to overcharge a lawn mower battery when the charge voltage exceeds the recommended value. This may result from using an incorrect charger. The overcharged battery may overheat, spew toxic fumes and even explode.

A riding lawn mower has additional features that require a battery to run. This includes the engine ignition system. Winter storage necessitates battery charging before using the mower. A riding lawn mower won’t start when the battery is flat.

You should charge the battery to use it. If this doesn’t help, it means your mower’s battery is completely dead, and the only solution is to replace it. How long a lawn mower battery lasts depends on weather conditions and maintenance. A good battery should last 4 or 5 years.

Can you overcharge a lawn mower battery?

There is a great possibility of overcharging a lawn mower battery if you use an old model charger with no safety features. Consequences of overcharging a lead-acid battery include corroded cathodes, battery overheating, and the release of toxic fumes or a hazardous explosion.

Dangers are even more when you overcharge a lithium-ion battery commonly used in cordless electric lawnmowers. It can create unstable conditions inside the battery, increase pressure, and cause thermal runaway.

Overcharging a lead-acid battery should not be a concern if you use a modern charger that can automatically stop the charging process once the battery is fully charged. The right charger to use should at least have the following features.

  • Multiple charging mode settings, including slow, fast charge and jumpstart
  • Hookup failsafe mechanism to prevent improper connections
  • Integrated charging timer and automatic shutoff feature
  • Float modes for optimal charge conditions without boiling or overcharging
  • Controlled amp rates to meet the specific power need of the battery

Pro Tip: If you smell pungent gases or notice a bulge in the battery case when charging, then your battery is likely to be overcharging. The next thing you’ll want to do is to disconnect the charger immediately.

How to Charge a Lawn Mower Battery

Charging your lawn mower battery the right way will help prevent overcharging, accidental property damage or physical injuries to the operator. Below is how to charge your lawn mower’s battery:

1. Start with your safety

Wear thick work gloves, safety goggles and protective clothing. Next, disconnect the lawn mower spark plug cable to prevent the engine from accidentally starting. Check any recommendations in the owner’s manual regarding battery charging.

2. Locate the mower battery

Most riding lawn mower models have a battery under the seat. This may vary from one model to the other. Identify the positive and negative terminals of the battery and ensure they are clean. If you cannot see the battery, refer to the user manual.

3. Connect the charger to the battery

Connect the charging cables to the battery terminals starting with the positive side (terminal) and then the black negative charging cable to the black negative battery terminal. Do this while the charger is disconnected from the electrical outlet.

4. Toggle the charger to the right settings

Adjust the charger’s voltage setting to match the battery’s voltage capacity and possibly its amps. We recommend normal charging speed, even if the charger has a fast charging setting. You can toggle the charger to jump-start mode if the battery is not badly off.

5. Plug in the charger

Plug your battery charger into an electrical outlet. Before you set power on, countercheck everything to ensure you have not made any errors. Now power the charger by turning on the electric switch and letting the battery charge.

How long does it take to charge a lawn mower battery?

A 10-amp charger should take approximately one hour to charge your mower’s 12 volts battery. You could wait longer than this if your charger indicated that the battery is still charging.

There is no worry about overcharging your lawn mower battery if you use a modern charger that can auto-shutoff once the battery is fully charged. If using the old model charger, we recommend you don’t keep your battery charging for too long, as this can damage or reduce its lifespan.

Can you charge a lawn mower with a car?

If your lawn mower battery is in good enough condition to accept a charge, then you can jump-start your lawn mower using a car battery. After that, the mower’s alternator should keep charging the battery to its full capacity as you mow.

Here is how to charge a lawn mower battery with a car:

  1. Park your car close enough to the lawn mower so that jumper cables can reach from one battery to another. A riding lawn mower battery is usually under the seat; parking your car behind the mower makes everything easier.
  2. Set the brakes, turn off the car and open the hood. Access the battery in the mower and lift the plastic covers off the battery terminals on both sides.
  3. Connect the jump-start cable with one side of the red cable to the positive terminal of the mower battery and the other side to the car battery’s positive terminal. Next, connect the black cable to the negative terminal of the car battery and its other end to an exposed piece of metal on the body of the lawn mower.
  4. Let the current flow for about 5 minutes, and start the lawn mower without starting the car. Be sure to leave the car engine off. Your mower won’t start if its battery is completely dead.
  5. Finally, disconnect the jumper cables in the reverse order: black cable from the mower, then from the vehicle; red cable from the vehicle, then from the mower.

Final Thought

A battery is one of the important components of a riding lawn mower that makes it fully functional. You’ll need to charge the battery when it has gone flat, especially after the long winter storage.

Using an incorrect charger will result in overcharging a lawn mower battery. This comes with great dangers like noxious fumes, battery explosion and damage to the battery cells. Be sure to use a recommended charger for your lawn mower battery.

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