How to Test A Lawnmower Battery
Lawn mower | Guides

How to Test A Lawnmower Battery


Testing a lawnmower battery is not rocket science. If your riding mower can’t start with ease, you need to be sure that its battery is functioning properly.

This guide gives you step-by-step instructions on the best method you can use to test the battery.

Testing A Lawn Mower Battery


You may want to ask, ‘how do I know if my lawn mower battery is bad?’ The simple answer is to test it. Testing a lawnmower battery is possible using two techniques;

  • Multimeter testing
  • Visual inspection

How To Test Lawn Mower Battery With a  Multimeter (Step by Step)


Step 1: It is essential for you to know the location of the battery so that you will be able to get the testing process right. Check your manual for a guide on its location. Ideally,  the battery of the riding mower is beneath the seat, and before you can gain access to it, you need to take off the seat. You can also find it in the engine cover, hood or behind the engine.

Step 2: Switch on the ignition without putting on the engine, and turn on the lights to eliminate the battery’s surface charge. If you leave the mower’s lights on for about a minute, you will be able to get a more precise reading when connecting the multimeter.

You need to note that you can skip this step if the light is dim when you turn the light on without starting the engine, meaning that the charge on the battery is low. You can go ahead to connect the multimeter immediately.

Step 3: Since the majority of the batteries of riding lawnmowers come with 12-volt batteries, put the multimeter to 12 volts. Some mowers come with 6-volt batteries, hence, it is important to check the manual to know the right lawn mower batteries voltage. If it is a 6-volt battery, you should set the multimeter at 6 volts.

Step 4: It is now time to link the multimeter with the battery. Some multimeters come with clamps, which you can affix to the terminals of the battery while others have needle-like metal pieces for convenient holding against the battery terminals.

The multimeter wires, as well as probes, are distinguished by colours as the red colour indicates positive while the black colour represents negative. It is essential to connect the multimeter to the battery terminals properly to get the most satisfactory result – the positive probe to the positive terminal (+) and the negative probe to the negative terminal (-).

Step 5: When you get the multimeter to battery connection right, the multimeter will display a reading that will let you know the condition of the battery. For a 12-volt battery, a reading of 12.6 volts and above is a sign of good battery health while a reading of 11 volts or less is a sign of bad health.

For a 6-volt battery, a reading of 6.6 volts and above means that the battery is healthy, and any reading of 5 volts or below is a red flag. You should replace the battery immediately if the test shows that it is not healthy. Charge the battery properly before the test so that you will be able to get an accurate reading.

Visual Inspection Of The Lawnmower Battery


Visual Inspection Of The Lawnmower Battery

A thorough visual inspection of the battery can help you to determine if it is still good. Here are what to look out for during the inspection so that you will be able to make the best decision.

Swelling or bulging: The build-up of gas inside the battery’s case leads to swelling or bulging. A swollen battery is dangerous as it can blow up causing you to injure and leading to damage to the engine. Hence, you should get rid of a swollen battery immediately, especially with the aid of a professional because of the risk factor.

Broken terminal post: If any of the terminal posts are damaged or broken, it means you need to get a new battery. Usually, the acid in the battery may corrode the terminal, which leads to a broken terminal.

When the terminal post breaks, there will be a system short circuit, which is not safe because it can get the lawnmower’s wiring burnt. Repairing a broken terminal post is not the best option, you need to replace the battery.

Cracks in the casing: Take off the battery from the mower to be sure that its casing has not cracked. Taking it off will enable you to look closely for effective identification of any damage signs. Use a cloth to wipe off dirt so that it will easier for you to spot cracks.

Replace the battery instantly if there are signs of leaks or cracks, especially if it is under warranty. If it is not under warranty, spending extra on replacing it will save you from danger. It is important to always put on your safety gloves and glasses when dealing with a battery. Also, you should not put an acid-leaking battery on a wooden surface because it can lead to spoilage.

The low water level: If your machine uses a flooded battery, you will need to constantly keep a particular level of water through the addition of distilled water regularly. With the aid of a water level indicator, which is situated by the side of the battery, you will be able to monitor the water level effectively.

A reduction in water level for an extended period can lead to a reduction in the charging capability and retainment of the battery. You should refill with distilled water, and let it charge for about eight hours. In a situation whereby the battery does not charge after the addition of water, you may need to change because it may have been destroyed by consistent low water level usage.

Testing under load: Load testing reveals the capacity of a battery to maintain voltage under the application of load. You can use the mower’s headlights to determine the health of the battery. Follow the two steps below to carry out the load test.

Step 1: Turn on the ignition of the battery without starting the engine, then put on the headlight. This is best done at night so that it will be easier for you to monitor the headlight.

Step 2: Start the engine and watch the headlight’s brightness. You can ask someone to start the engine while you monitor the headlight. If the headlight dims significantly or turns off, it means that the battery is weak.

Also, if the engine cannot start when the headlights are on, it is a sign of weakness. Take note that momentary dimming of the headlight is normal as the engine is put to start because of the high current requirement for starting an engine.

How To Charge A Lawnmower Battery?


How To Charge A Lawnmower Battery

Another question that comes to your mind is probably ‘how to restore a lawn mower battery?’

The simple answer is ‘charge it’. Charging your battery is as easy as ABC, and the following 5 steps will help you to get it right in terms of effective charging.

Step 1: Get a good charger, especially the new 12-volt smart charger because of its automatic state-of-battery detection feature. This helps with direct charging following the battery’s condition. The smart charger will charge your battery as long as it is connected,  and when the battery is full, it stops charging automatically.

Step 2: If there is a socket near the mower for plugging the charger, you can use it to charge the battery while in the machine. If this is not the case, take off the battery and plug it into an available socket through a good charger.

Step 3: Clean the terminal posts properly before connecting the charger to the battery. Use baking soda as well as distilled water to make the terminals clean. Mix two tablespoons of baking soda with water till you get a thick mixture, and rub the mixture on the battery’s terminals with the aid of a clean cloth.

Step 4: Unplug the charger from the socket and connect it to the battery. Make sure that the charger’s positive cable goes first to the battery’s positive terminal before connecting the negative cable to the battery’s negative terminal.

Step 5: Plug the charger into the socket and instantly the smart charger will let you know if the connection is perfect. If the connection is perfect, it will start charging instantly, and when it is full, you will get a notification. Endeavour to put the battery in a dry place if you want to connect it to the charger for winter storage.

Frequently Asked Questions

Is a lawn mower battery 6v or 12v?

The majority of lawnmowers utilizes 12-volt batteries but will find 6-volt batteries in models released before 1980.

What voltage is a riding lawn mower battery?

Many riding mowers come with 12-volt batteries. However, some boasts 6-volt batteries, especially models developed before 1980.

How to remove a lawn mower battery?

It is easy to remove a battery from a riding lawnmower, you only need to disconnect the positive and negative terminals carefully, and you are good to go.

Can you start a lawn mower while charging the battery?

It may be counterproductive starting your mower while charging the battery. While there is no risk involved in this practice, it may reduce the lifespan of the battery.

Bottom Line


Testing the battery of your lawnmower is a perfect thing to do at the beginning of a mowing season. This will guarantee optimum preparation for the new season for maximum effectiveness.

A weak or dead battery will negatively affect your mowing jobs for the new season, hence, you should prepare adequately.

Last Updated on May 10, 2021

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