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

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

Yes, a lawn mower battery can get overcharged if left connected to a charger for too long. Overcharged battery may overheat, spew toxic fumes and even explode. You can avoid this by investing in a modern type charger that automatically shuts off when a battery is fully charged.

A riding lawn mower has additional features that require a battery to work. While most of them come with a battery charging system, longer storage or a problem in the system can lead to insufficient charge in the battery. A dead battery can be a reason why a riding lawn mower won’t start or stall in the midst of mowing.

The only way of getting your lawn mower back to life is charging the battery using an external source or jumpstarting your lawn mower with another battery. If this doesn’t help, it means your mower’s battery is completely dead and the only solution is to replace it.

Further, how long a lawn mower battery last will depend on its lifespan age, weather conditions, storage and how you maintain it. A good battery should store charge for up to 3 weeks and last for 4 or 5 years.

Can you overcharge a lawn mower battery?

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

Dangers are even more when you overcharge a lithium ion battery commonly used in cordless electric lawn mowers. It can create unstable conditions inside the battery, increase pressure, and cause thermal runaway. These are irreversible damages that will send you back to the market in search of a new battery.

Overcharging a lead acid battery should not be a concern if you are using a modern charger with the ability of automatically stop the charging process once the battery if 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 condition 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 in preventing 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. Finally check any recommendations in the owner’s manual regarding battery charging.

2. Locate the mower battery

In most riding lawn mower models, the battery is located under the seat. This may vary from one model to the other. Identify the positive and negative terminal of the battery and ensure they are clean. If you are unable to see the battery, then refer to the user manual.

3. Connect charger to the battery

Connect the charging cables to the battery terminals starting with the positive side (terminal) 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 always recommend normal charging speed even if the charger has fast charging setting. If the battery is not badly off, you can toggle the charger to jump start mode.

5. Plug in the charger

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

How long to charge lawn mower battery?

A 10-amp charger should take approximately one hour to charge your mower’s 12 volts battery. You can wait longer than this if your charger indicated that the battery is still charging. But again if your lawn mower has a charging system, one hour charge will keep everything mowing as the battery will also be getting charged.

There is no worry about overcharging your lawn mower battery if you are using a modern charger that has the ability to auto-shut off once the battery is fully charged. If using the old model charger, we recommend that 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 enough good condition to accept a charge, then you can jump-start it using a car. After that, let the mower’s alternator should keep charging the battery to its full capacity as the mower runs. If left hooked up on a car, the battery will overcharge, boil or even burst.

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 in both sides.
  3. Connect the jump-start cable with one side of red cable to positive terminal of the mower battery and the other side to the positive terminal of the car battery. 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 exact reverse order: black cable from mower, then from vehicle; red cable from vehicle, then from mower.

Final Thought

A lawn mower in an expensive investment that helps in keeping grass neat in the yards, park and gardens. A battery is one of the important component of a riding lawn mower that makes its fully functional. You’ll need to charge the battery when it has insufficient charge to start and keep your lawn mower running.

There is high chances of overcharging a lead-acid or lithium-ion battery when you use incorrect charger. Dangers include permanent damage to the battery or personal injuries resulting from noxious gasses or battery explosion. To avoid this, invest in a modern charger or jump start your lawn mower using a car as explained in this guide.

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