Lawn Mower Batteries Explained

You may have owned and used your share of push-style lawn mowers over the years. You know the drill: You make sure there’s plenty of gas in the tank, and you pull the cord. On a good day, the mower will start after one pull. As the mower ages, or as wear and tear sets in, it may take a few more pulls. Newer riding lawn mowers don’t require this sometimes-frustrating action but instead use a battery. A lawn mower battery can make it easier to start the machine and get started on your task faster. If you've used a push mower, this is likely a welcome change. It’s helpful to understand some similarities and differences between these batteries and the ones you might find in your car or truck.

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Battery Overview

Many ride-on lawn mower models feature a starting battery and alternator. There’s also a voltage regulator on the mower to keep it charged and ready for the next use. otherwise you’d end up with a dead battery. This may not be as inconvenient as being stranded in the middle of nowhere in your vehicle. But, you certainly don’t want to be sitting on your mower on a lawn of overgrown grass with a battery that doesn’t have the juice to get the machine started.

How the Battery Is Different Than a Car Battery

When you need to buy a new battery for your lawn mower, you don’t want to head to your local auto parts store and pick out just any product. Your machine will require a specific battery with the right specs to power the mower. Shopping online can make your job easier, as you can filter your search for lawn mower batteries. These batteries are smaller than a car battery. Another key difference is the mower battery can last longer than a car battery. In fact, if you properly maintain the battery and take good care of it, you shouldn’t have to replace it for years. Of course, you probably won’t use the lawn mower nearly as often as you start up your vehicle. Still, even with much less frequent use and a lot of sitting idle in your garage or shed, the battery should be as effective in five years as it is today.

You’ll also love that lawn mower batteries won’t cost as much as a car battery. This difference can help your pocketbook now when you need to purchase a new one and in the long run, as you won’t need to buy one as often. Mower batteries don’t require a starter with the same size starter as a car, either. This means the cold crank cranking amps (CCA) are about one-third of what you would find with a vehicle.

Similarities Between a Lawn Mower Battery and a Car Battery

Though your lawn mower battery is powering a completely different machine than a car, there are some features that resemble those of a vehicle battery. You’ll have to pay attention to corrosion issues with your mower battery, just as you would with a car battery. This is because a mower battery has comparable acid content and antimony. You should clean off the corrosion buildup from the terminals often. You can do this with hot water, baking soda, and a toothbrush. Doing this can improve performance and help it last longer.

A car battery uses cells with lead plates to power it. These cells are submerged in an acid electrolyte. Your motorcycle battery will act similarly. Also, sulfate covers the plates, and the acid turns into alkaline when the battery discharges. As it charges again, the sulfate will return to the acid electrolyte and it becomes acidic. This process is much like what you would find with your car battery.

Though the battery in your lawn mower is physically smaller than the one in your car, it will also run on a 12-volt electrical system.

How to Choose the Right Battery: Ratings and Size

As you start shopping for a battery for your mower, you’ll probably ask, “How are lawn mower batteries rated?” These, too, use the CCA measurement. CCA is an indication of how much current the battery is capable of sending at zero degrees Fahrenheit in 30 seconds. While you may have attempted to start your car in these cold temperatures, it’s difficult to imagine why you would need to mow your lawn under these conditions. Still, the ratings can give you a good idea of the battery’s capabilities and reliability, even after years of use.

For a typical riding lawn mower, you would want to shop for something that has at least 145 CCA. However, larger models with bigger engines of more than 12 horsepower will require a battery with up to 300 CCA. To make sure, you can check the old battery’s label, or the owner’s manual or manufacturer’s specifications for your mower. The vast majority of lawn mower batteries are all very similar and part of the U-1 group size. These consist of U1, U1-R (reverse posts) and the rarer U1-3 which is simply a higher cranking amp version.

When it comes to their ratings, you’ll notice that most batteries are rated according to their size. Your mower battery will probably fall into the Group U1 category, which means it is 8.3 inches long, 5.1 inches wide, and 7.25 inches high. Don’t disregard this size description; it’s important that you can fit the battery comfortably and firmly in the tray and engine compartment. You’ll need to be able to connect the battery cables to it as well.

Handle with Care

Use caution when you handle your mower battery. As it contains acid, it is hazardous. Hold it upright and don’t drop it or treat it carelessly. When you remove your old battery, don’t simply toss it in the garbage. Just like with your car battery, make sure you dispose of your mower battery properly by taking it to an AutoZone.

When you’re shopping for a lawn mower battery, make sure it has the right CCA rating and fits correctly into your machine. There’s no reason why this product shouldn’t serve you well for many years and countless uses. Cut your grass dependably with a mower battery you can feel good about. If the job is too big for you, seek out one of our Preferred Shops to help you do the job.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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