All About Lawn Mower Batteries

For bigger garden tractors, the days of the old rip-cord recoil starter are mostly over. Larger riding mowers now feature a battery for starting. They also have a basic alternator and voltage regulator to charge the system, keeping the battery topped up.

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How Are Lawn Mower and Automotive Batteries Different?


Lawn mower batteries have an obvious form-factor difference compared to your car’s battery, but there are also a lot of similarities:

  • Like automotive batteries, most lawn mower batteries use a series of lead plates submerged in an acid electrolyte.
  • While the battery discharges, the plates will become covered with the sulfate anion and the acid will become more alkaline. While it recharges, the sulfate in the plates move back into the acid electrolyte and makes it acidic.
  • New mower electrical systems operate with a 12-volt battery.

The design of the lead-acid battery is over 100 years old now. Even with its long history it still has some remaining problems. The primary issue is that it is hazardous to handle, to maintain, and is potentially a risk during disposal. Although their now are robust recycling programs in place to handle them. The batteries are not as well isolated on a mower to absorb the constant vibration of the engine, compared to¬† a battery in a passenger car’s engine compartment would be.

A slightly newer battery technology is available on some newer mowers. These batteries feature an absorbed glass mat (AGM) or gel cell design. This AGM is a significant advancement in limiting the amount of liquid in the battery for safer handling.

How Are These Batteries Rated?

A lawn mower battery is rated based on cold cranking amps (CCA). The CCA rating is a measurement of how much current the battery can deliver over 30 seconds at 0 degrees Fahrenheit. Unless you have a plow or snow-blowing attachment for your garden tractor, you probably are not likely to be running your mower in zero-degree weather, but the CCA will give you a good indication of how robust the battery will be and what to expect.

The Battery Council International rates or classifies batteries by their physical size. Most mower batteries fall into Group U1, which sets out a standard size of 8.3 inches long, 5.1 inches wide, and 7.25 inches high. These dimensions are important, as the battery has to sit in a tray in the engine compartment properly, and must be able to connect to the wires to the battery terminals.

For mower batteries you ultimately will get what you pay for. Buy for the quality level and service life that you need. Make sure to match the location of the terminals on the original battery. Be sure sure that the replacement battery has at least as many CCAs as the original. If you want to save time and money in the future, the best way is to extend the life of your lawn mower batteries by hooking up a battery tender over the wintertime. Check out our other article on how to keep your battery charged.


Select a Battery for your Lawn Mower