How to Charge a Lawn Mower Battery with a Car Battery

A lot of people with a lawn mower and a car often wonder if the battery of the former can be charged with the latter’s charger. If you’re one of those, you have come to the right place for answers.

It is not unusual to wonder if you can charge your lawn mower’s battery with your car. After all, they are both vehicles that run on batteries right? Well, that is true. You can do it and there is a tried and tested way to get it right too. Here’s all you need to know about that.

You can do this with jumper cables. Turn your car off, get it closer to the lawn mower and connect the cables. Start by connecting the red lead to the positive terminal and then the black lead to the negative terminal. Once the lawn mower gets started, disconnect the black cable first and then the red cable. You are good to go.

But there are a few precautions to take and a couple of other things to consider before you head towards your car and get the jumper cables out. So, keep reading to make sure you don’t accidentally fry your mower’s battery.

Can I Charge a Lawn Mower Battery with a Car Charger

The fact that it uses a battery is one of the few things a lawn mower has in common in other everyday vehicles like cars. So, it is natural to be curious if you can charge the lawn mower’s battery with a car’s charger.

The simple answer to this question is yes. And you can do it using jumper cables. But there are a few ifs and buts that you should keep in mind so that you don’t fry the little guy’s battery.

One of the most important ones to remember is to keep your car turned off while you connect the batteries. This is because your car has a lot more output than the lawn mower needs. So, if you turn it on while trying to get the lawn mower started, you risk overheating the battery of your lawn mower and hence damaging it.

Now, while you can do this safely at home on your own, before you get started with the process you should remember that this works only if your lawn mower has 12-volt batteries. And there are some safety precautions to take.

Safety Precautions Before You Get Started

Make sure you are wearing protective gear like glasses and gloves before you get started with the batteries of either machine. And when you are done, wash off any powdery substances or greases you may find on your gear as soon as you can.

If you see that there is a crusty layer on the battery posts, make sure you clean them before you get started with the jump starting. This is because it is harder to work with dirty battery posts. The layer on the posts and even on the batteries for that matter is caused by corrosion which happens over time and it makes it difficult to establish a good electrical connection.

Don’t try jump starting the 6-volt batteries in your lawn mower with your car battery because that is more power than what the batteries are made to handle and will kill the battery.

If the connection is loose or the lawn mower does not have enough gas, the jump-starting might not work. Be sure to check that before you increase charging time to get the lawn mower running. It is also possible that the battery is dead in which case this might not work.

Method 1: Using Jumper Cables

Step 1: Get your car close to the lawn mower so that the jumper cables can comfortably be connected to it without being strained.

Step 2: Locate the battery of the lawn mower. Usually, it is under the seat which means the car must be right behind the lawn mower instead of in front of it.

Step 3: Turn off your car before you get started. Open the hood of the car and locate the battery compartment of the lawn mower. Remove any other components like the plastic covers on the terminals of the battery because they might get in the way. This applies to both vehicles.

Step 4: Connect the cables one after the other. Locate the positive terminal on the lawn mower battery and attach the red lead to it. The other end of the lead goes into the positive terminal of the car battery.

Step 5: Locate the negative terminal on the lawn mower battery and connect the black lead to it. Then connect the other end of the lead to a piece of metal to the lawn mower.

Step 6: Start the lawn mower first and if it does not start, give the connection a minute or two because it is possible that the lawn mower battery is dead. Leaving the cables connected will help resuscitate the dead battery.

Step 7: When the lawn mower starts running, remove the cables in the opposite order in which you connected them. That means, disconnect the black and negative terminal first and then do the same for the red and positive terminal.

This should get your lawn mower going. Quite easy, isn’t it? But there might be times when you don’t have the jumper cables lying around. Even in such cases, you can use the car battery to get your lawn mower running. Here’s how that is done.

Method 2: Without Jumper Cables

If you do not have jumper cables lying around, here’s how you do it.

Step 1: Get the battery of the car out of its compartment and the vehicle safely. Place it on the lawn mower safely.

Step 2: Connect the battery terminals of the lawn mower to the car battery with a firm grip and try to turn it over.

Step 3: Once the lawn mower gets started, you can remove the connections and use the lawn mower.

Frequently Asked Questions

Can You Charge a Lawn Mower Battery with a 12-Volt Charger?

Most of the modern lawn mowers have 12-volt batteries and they can be juiced up with a charger of the same voltage. But if your lawn mower was manufactured before 1980, it might have a 6-volt battery in which case a 12-volt charger just won’t do.

The thing to remember here is to find a charger with the same voltage as your battery. And even then, get something that gives an output of less than 10 amps so as to not damage the battery.

Can You Recharge a Dead Lawn Mower Battery?

Yes, absolutely. This usually happens when you leave the lawn mower unused for a long time or during winter. You can easily revive the battery by using its charger for a few hours. But if you want to try and jump start it, you might want to get a multimeter and determine whether it is dead or if there is a problem with any other part of the electrical circuit.

You can also figure it out by locating the clutch. Depress it and turn its key. If the engine doesn’t start, it is likely that the battery is dead. That is also the case if the lawn mower 

How Long Does It Take to Charge a Lawn Mower Battery With a Trickle Charger?

It takes longer to charge a lawn mower using a trickle charger than a regular one because it has low amperage. This way, it can maintain the charging level but it takes a lot longer for it to bring the battery to its full capacity.

But if you keep it connected for too long, the battery might overcharge and emit poisonous gasses. It is recommended to leave the charger on overnight if you have a smart charger that detects when the battery is at full capacity and switches off automatically.

Otherwise, it depends on how much charge is currently there in your lawn mower’s battery.

About the author, Phil Borges

Phil Borges is a battery aficionado. He's written extensively about batteries, and he loves nothing more than discussing the latest innovations in the industry. He has a deep understanding of how batteries work, and he's always on the lookout for new ways to improve their performance.