Can I Charge A Lawn Mower Battery With A Car Charger? (Explained)

Lady on riding mower mowing lawn

There are few things in life more frustrating than a dead battery.

Especially when you are all set to get your lawn looking spick and span.

That is why in situations like this people want to know if they can charge a lawn mower battery with a car charger.

In principle, it sounds like it MIGHT work.

But how does it play out in practice?

Let’s find out.

Can I Charge A Lawn Mower Battery With A Car Charger?

The larger batteries found in riding mowers generally can be charged from a car, with the process similar to jump-starting a dead car battery. However, batteries from smaller push mowers should not be charged in this way as they won’t be able to handle the current coming from the car.

You Can Charge the Battery of a Riding Mower From a Car Battery

Most riding lawn mowers use 12v, lead acid, car/ATV type batteries, which means if your battery is dead on your riding mower you can use your car battery to jump start it.

The exception to this is if your riding mower uses a lithium battery of any voltage, then you will need to use a charger designed specifically for lithium battery charging.

Otherwise, as long as the mower system is 12v you are good to go. Most riding lawn mowers made after 1980 have 12v batteries, but check before you start!

Why would you use a car to charge your lawn mower battery?

Well most modern battery chargers need to detect a voltage before they start charging.

So if your battery is completely dead, there will be nothing to trigger the battery charger.

Connecting it to your car battery can start the charging process.

How To Do It

If you have ever jump-started a car, then the process of using a car to charge your riding mower’s battery isn’t too different.

But to help we have broken it down into 5 easy steps (and also included a video above!):

Make sure your mower has a 12v battery and then make sure both vehicles are turned off and the brakes are on. Lift the plastic covers off of the battery terminals on both batteries. Attach standard jumper cables from your car battery to your mower battery in the following way:

  • Attach the red clamp to the positive terminal of the car battery.
  • Attach the red clamp at the other of the same lead to the positive terminal of the mower battery.
  • Attach the black clamp to the negative terminal of the car battery.
  • Attach the other black clamp to the frame, or an exposed piece of metal, on the mower. It is attached here rather than the terminal as any electrical issue will dissipate into the metal frame.

RELATED ===> Buyers Guide: The Best Riding Lawn Mowers on the Market

Start the mower. If the mower doesn’t start, leave the batteries to continue the charge for a couple of minutes and then try again. At no point should you start the car as the vehicle’s electrical system will overload the mower’s battery.

When your riding mower starts, leave the batteries connected for a few more minutes (around five should be sufficient), to give the previously dead battery a bit more juice.

Leave the mower running and after around five minutes disconnect the batteries in the reverse order you connected them, so:

  • Remove the black clamp from the frame of the mower.
  • Remove the black clamp from the car’s battery.
  • Remove the red clamp from the mower’s battery.
  • Remove the red clamp from the car’s battery.

Get mowing your lawn!

You Should Never Charge Other Batteries With a Car Charger

Lawn mower on grass

Trying to start a dead battery that is not 12v in size with a car battery is most definitely not recommended.

Batteries for standard electric push mowers are often something in the 40v or 80v range.

When these batteries are dead they can be badly sulfated, which means they won’t be able to tolerate the current coming in from a car battery.

Or even if the battery is in a good condition, it should not be hooked up to a much larger battery due to the size and voltage difference.

RELATED ===> Will a Lawn Mower Battery Start a Car?

At best nothing will happen, at worst the larger battery will destroy the smaller battery, possibly anything nearby and worst of all, possibly you as well!

Smaller batteries are often interchangeable between machinery, they can be swapped between mowers and string trimmers for example.

That means they are often cased in some kind of protective housing. This is another sign you should not attempt to jump-start them.

Dangers of Using a Car Charger to Charge a Mower Battery

Whilst a car can be used to revive the dead battery of a riding mower, it isn’t something that should be done regularly.

Each time you jump start a battery you are applying a lot of voltage and placing unnecessary strain on the internal components.

The more often you do this the more rapidly your battery will decline in performance.

It could also destroy the diode in the electrical system of your mower, as it is a lot of power for it to handle.

Also remember that you are draining the car battery whilst you use it to charge the battery of your mower, so you could then end up having to jump-start the car!

Two good alternatives are:

  • A Jump Pack
    This is simply an external battery with jumper cables, that is designed to work with 12v batteries. Jump packs hold a charge via a hard-wired connection and reduce the risk of damaging your mower battery.
  • A Battery Charger
    Battery chargers ensure the charging battery doesn’t charge too quickly or overheat. When the battery reaches a certain level of charge it slows the input current and trickle charges. Again it is a safer way of charging your mower battery.

RELATED ===> Can You Push Start A Riding Lawn Mower?

Final Thoughts

Can I Charge a Lawn Mower Battery With a Car Charger Infographic

You can charge the battery of a riding mower from a car, as the larger 12v style batteries riding mowers use are compatible with car batteries. We have outlined this in the infographic above.

The process of doing so is akin to jump-starting a car when it has a dead battery.

However, you should never try and charge the batteries found in smaller push mowers from a car, as they won’t be able to tolerate the incoming current and the result could be catastrophic!

Even charging larger riding mower batteries should be done with caution and as more of a last resort.

Charging riding mower batteries from your car on a regular basis will degrade both the mower battery and the car battery and isn’t a good idea.

However as a one-off, it could be a lifesaver for you!

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