Will a Lawn Mower Battery REALLY Start a Car? (Explained)

A 12V riding mower or lawn tractor battery could be used to jump-start a smaller vehicle in an emergency. You could even possibly put a riding mower battery in a small car and jump start it. However large vehicles will be more demanding and a mower battery is unlikely to have enough CCA to get them started.

Can You Put a Lawn Mower Battery in a Car and Jump Start It?

Ok so let’s deal with the first way of approaching the issue of whether you can start a car with a lawn mower battery.

For it was this scenario that lead me to write this blog.

And when I talk about a lawn mower battery I mean a 12v lead acid battery, not a lithium-ion battery you find in battery-powered push mowers.

So last week I bumped into an old school friend of mine who had moved away, and who I hadn’t seen for a while.

When I saw him, my mind went back to a story he told me years ago.

He had a 1.3L Toyota Corolla. It was in a dire need of a new alternator and battery. In fact the battery was completely dead, nothing could get is started.

He needed to find a way of getting it the 20 miles or so to the auto repair shop and didn’t really fancy paying someone to tow it there or even getting a friend to tow it all the way.

So he had a brainwave and took the battery out of his 18.5hp Craftsman riding mower and put it in his car, and gave it a jump start.

Without much in the way of expectations, he turned the ignition and, to his surprise, the car just about wheezed into life.

He then managed to drive it to the garage, and get the alternator and battery replaced.

As a bonus, the battery served his riding mower without problem for another couple of years.

So I guess that answers the question, yes a lawn mower battery can start a car, but it does depend on a number of things.

Both cars and riding mowers used lead-acid 12V batteries, which is a good start!

And, in essence, as long as it is a 12v battery, and it has a decent AH capacity and enough cold cranking amps (CCA) to spin over the engine, a car will charge it as it would any 12v battery.

In fact if you look at Miata Forum, you will see many instances of owners using lawn mower or lawn tractor batteries long-term in this Japanese car.

What makes it especially convenient in the case of Miatas and some other lightweight roadster sports cars is the fact that riding mower/lawn tractor batteries are almost identical in size and shape to OEM Miata batteries, but a lot cheaper.

So yes a riding lawn mower battery could be put in a car to start it, but it won’t always work (I think my friend got lucky that he had a relatively small car).

It most definitely won’t work as a long-term solution in most cases, as there are a number of potential issues that we will go into shortly…

Can You Jump Start A Car With A Lawn Mower Battery?

Again the answer here is similar to that above.

In good conditions, and with a fully charged riding mower/lawn tractor battery, it could well have enough CCA to start a car, providing we are not talking about a particularly large and powerful vehicle (see the video above!).

If the vehicle’s battery isn’t completely dead it will only need a second of current surge to go through it to kick it into life.

To ensure a higher likelihood of this method working, if you keep the mower/tractor running, the alternator will help keep the battery at full charge.

In short it is a case of, it might work but there is no guarantee and there are some things to be aware of…

Using a Lawn Mower Battery to Start a Car: Potential Issues

If you are considering using your lawn mower battery as a way to start your car, there are some things to seriously consider before you do so.

Size

First of all, if you are thinking about putting it into your car there is the issue of the physical size of the battery.

Mower batteries and car batteries whilst operating on the same voltage will vary in size and you will have to find a way of fitting it in to your car.

Then there is the issue of whether the battery cables are long enough.

In the case of the Miatas mentioned early, lawn mower batteries work as they are a similar size and shape, and the Miata is a relatively light-impact car.

CCA and CA

Cranking amps (CA) tell you the power your battery can provide when starting a vehicle in moderate temperatures (32° F and above).

Cold-cranking amps (CCA) essentially tell you the power a battery can provide in colder temperatures.

Cold weather makes it more difficult for a battery to start the engine of any vehicle, as cold weather means the battery produces less electrical current.

As you can imagine a battery for a riding mower or lawn tractor has a lower CCA rating as it is smaller and much less demanding to start than a car.

The best riding mower or lawn tractor batteries might have a rating of 300 to 320 CCA, but it can vary hugely going down to around 100 CCA at the other end of the spectrum.

The good news is smaller cars might require as little as 150 to 200 CCA to get them started, whereas as pickup trucks and SUVs will need around 400 to 500 CCA.

If the battery doesn’t have sufficient capacity, the likelihood is that trying it will simply discharge the battery.

However, in a worse-case scenario, you could end up severely damaging your lawn mower trying to jump-start your car with it.

So you need to bear that in mind.

Weather

As mentioned above trying to start a vehicle in cold weather puts much more demand on a battery.

So if you try to jump-start your car using your riding mower when it is cold, the likelihood of success is even lower.

Is A Lawn Mower Battery the Same as a Car Battery?

We have touched on this already, but riding mowers/lawn tractors and cars both use 12V lead acid batteries.

But the batteries are tailored for the vehicles they are in.

Batteries for riding mowers are smaller and easy to crank. That is because the loads on a mower are lower, which means the alternator can meet them more easily and charge the battery.

Riding lawn mower batteries are also cheaper.

Then we have battery-powered, push mowers.

These use a different battery type completely, which is lithium ion and a different voltage.

You should never try using one of these in your car/to jump-start your car!

Final Thoughts

Will a Lawn Mower Battery Start a Car infographic

In theory, a lawn mower battery can be used to start a car.

But there are several warnings I would add before trying to do so, and in reality, I would use it more as a last resort.

It could work for smaller cars in nice weather, providing it is a 12V battery with a good capacity.

But as you try to start larger vehicles the likelihood of success diminishes, as the lawn mower battery may not have enough CCA to meet the higher demands of bigger cars/trucks.

It does seem like numerous owners of Miata cars use lawn mower batteries in their cars. Miata cars are smaller and less exacting vehicles.

And in an emergency, as was the case with my friend, a lawn mower battery might even prove a temporary savior.

But it shouldn’t be thought about as a long-term solution.

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Will a Lawn Mower Battery Start a Car?