What keeps draining my lawn mower battery? Diagnose&Fixes

Does your lawn mower battery drain faster than it should? This is a common issue, and we have the answers. Our comprehensive guide will help you understand the problem and how to fix it. Let’s power up your lawn care routine.

Using accessories that exceed the mower’s charging capacity can drain the battery, so unneeded devices should be turned off. Corroded battery terminals, a faulty voltage regulator, and a weak stator that fails to charge the battery properly can also cause repeated draining.

Read on to learn how to keep your lawn mower’s battery from draining too quickly. We’ll explore the common causes and provide practical solutions. Let’s get your lawn care routine back to its peak efficiency.

The function of a battery in a lawnmower:

The battery performs two prime roles in the lawnmower:

1. Starting the lawnmower: To provide the requisite electrical power needed to create the lawnmower.
2. Power other equipment: To provide a reference point (ground) for the lawn mower’s electrical system controlling almost all the electrical equipment.

Suppose the lawn mower’s electrical system and the battery are in perfect condition. In that case, the battery shall provide the initial start-up power to the lawn mower’s engine, and when the engine is running, it shall charge the battery simultaneously. But a snag in either of the two causes battery drainage.

We shall provide an in-depth analysis of the reasons that can cause battery drainage. What kind of tools do you need to test it and find the leading cause of drainage?

Causes of Lawnmower Battery Drainage:

● Reason 1: More power usage than lawn mower’s electrical system capacity

Some lawnmowers are created to be used as lawn tractors or small snowplows. While performing these tasks, one must use trailer lighting, headlamps, or other extra functionalities.  

Suppose the lawn mower’s engine merely produces the energy required to charge the battery. In that case, these different devices suck the power that was to be used to charge the battery.

– Fix: Using less power

If that’s the case, all the lawnmower equipment that performs unnecessary functionalities must be turned off during the lawnmower’s operation. This step is done so the battery may receive the total power required to revive itself.

If turning off is impossible, you could leave the mower running after you finish with all the appliances turned off to recharge the battery.

● Reason 2: For Lawn Mower Parasitic electrical drain

Electrical System: The lawnmower’s electrical system may drain the battery while the lawnmower is turned off. The electrical system may resume drawing current from the battery due to an unwanted connection in the system.

This connection can be due to parts touching each other, moisture, or other reasons.\

– Relay equipment turned on:

The drain may also be caused because some electrical relay equipment remains turned on even if the lawnmower is switched off. These devices draw unnecessary electric current and rob the battery. Some equipment has a standby mode that uses power.

– Test for an unnecessary current draw:

To check whether current is being drawn from the battery while the lawnmower is turned off, we need to perform a test using a multimeter by following the following mini procedure with steps:

• Step 1: Set the multimeter to ammeter mode.
• Step 2: Place the multimeter’s positive terminal on the battery’s positive terminal and its opposing end to the battery’s negative.
• Step 3: Suppose the ammeter shows a value greater than 1mA. In that case, the electrical system draws power from the battery while the lawnmower is off.

– Use the multimeter resistance mode:

Finding the cause of parasitic electrical drains can be challenging. Another method to find the reason is using the multimeter’s resistance mode. Disconnect the battery, turn off all appliances, and remove as much as possible. Then, measure the resistance between the two battery connectors.

Reattach the appliances (still turned off) and check if you can see a difference in resistance. Also, check that moisture is not the cause. You can do that by parking the lawnmower in a dry location and checking after some time.

● Reason 3: Corroded battery posts:

Another possible reason for battery drainage is corroded battery posts. A white, crusty powder might also form around the battery’s terminals. This causes the battery to put in extra effort, which causes the battery to drain faster.

So, the battery posts and terminals should be cleaned regularly with a clean cloth. Also, loose connections of battery terminals to battery posts may cause battery drainage, so don’t forget to tighten them regularly.

● Reason 4: Voltage regulator problem

A voltage regulator’s function in a lawnmower is to convert the engine’s voltage into the correct voltage and then supply it to the battery to charge it.

However, the voltage regulator may also be one of the causes of the lawn mower’s battery drainage. It may continue to draw current from the battery even after the lawnmower is shut down.

– Test to check if the voltage regulator is draining the battery:

To test if the voltage regulator is robbing the battery, you need to perform a test using a multimeter.

• Step 1: Set the multimeter to ammeter mode and place the multimeter’s positive terminal on the voltage regulator’s positive end. Then, touch the multimeter’s negative terminal to the lawnmower’s metallic body.
• Step 2: If the ammeter is above 10mA, your voltage regulator draws current from the battery, causing it to drain and short-circuit.
• Step 3: In this case, the voltage regulator needs to be replaced by a new one. Remember to buy the same model voltage regulator as the one being replaced.

● Test 1: Perform a voltage test on the voltage regulator

When a lawnmower starts, the flywheel inside its engine also starts its rotation. This flywheel is an alternator with magnets that create an A.C. voltage of about 30V. This A.C. voltage is fed into a voltage regulator that converts this 30V A.C. into about 15V D.C.

Which is then provided to the battery for charging purposes. One of the causes of battery drainage is that the voltage regulator might not supply enough voltage back to the battery. We need to test the voltage regulator to verify if this is the reason.

Consider the following instructions for testing the voltage regulator. First, ensure the lawnmower is turned off and disconnected from any power source. Next, locate the voltage regulator in your lawnmower, typically found near the battery or engine compartment.

– Using a Multimeter for the Voltage Test

Using a multimeter, measure the voltage output from the regulator while the lawnmower runs. If the reading is significantly less than 15V D.C., this could indicate a problem with the voltage regulator. It’s important to note that other factors can also affect the battery’s charge.

For instance, using natural ingredients like soil and herbicides containing high salt levels can cause corrosion or damage to the battery terminals, leading to poor electrical conductivity and subsequent battery drainage.

Therefore, regular cleaning and maintenance of the battery terminals are also crucial in ensuring the optimal performance of your lawnmower’s battery.

– Testing procedure:

• Step 1: Set your multimeter to D.C. voltage measurement mode.
• Step 2: Turn the key switch to the on position.
• Step 3: Remove the wire’s connection that supplies voltage to the battery. Place the positive terminal of the multimeter on the voltage regulator’s positive. And place the multimeter’s negative on the lawnmower’s metallic body.
• Step 4: The multimeter should display a value of about 12V, indicating that the voltage regulator supplies voltage back to the battery.
• Step 5: Suppose the multimeter shows a low or no voltage value. In that case, there is an issue with the voltage regulator. Hence, it needs to be replaced by a new one.

● Test 2: Perform a voltage test on the lawn mower’s stator:

The lawnmower stator supplies A.C. voltage to the voltage regulator, which then provides juice to the battery to charge up.

But in some cases, the lawnmower stator may not give sufficient A.C. voltage to the voltage regulator, which may be one of the possible causes of battery drainage. To verify if this is the issue, we need to perform a test on the stator using a multimeter.

– Testing procedure:

• Step 1: Set your multimeter to A.C. voltage measurement mode.
• Step 2: Start the lawnmower.
• Step 3: Remove the wire connection coming out of the stator from the voltage regulator.
• Step 4: Insert the multimeter’s terminals inside the stator wire’s terminals.
• Step 5: The multimeter should display a reading of about 30V. If the multimeter shows a reading below 20V, the stator must be replaced by a new one.

Related Questions:

1) How can I check if my lawnmower’s battery is dead?

When the lawnmower hasn’t been used for a year or more, there is a high probability that the lawnmower’s battery won’t have any juice left and may be dead. We can perform a simple test on the battery using a voltmeter to check that. The steps are as mentioned below:

• Step 1: First, you must charge the battery to its total capacity.
• Step 2: Now, set a multimeter to D.C. voltage measurement mode.
• Step 3: Place the multimeter’s positive terminal on the battery’s positive terminal and the multimeter’s negative on the battery’s negative.
• Step 4: The multimeter would show a reading of about 12V.
• Step 5: Next, leave the battery for about 30 minutes, and then again measure the voltage across the battery using a multimeter.
• Step 6: Suppose the reading shown by my multimeter drops to about 5V or less or decreases continuously. In that case, the battery is no longer functional and needs to be replaced by a new one.
• Step 7: While installing the new battery, please check if the battery is a regular terminal or reverse terminal and make connections regularly.

2) How do you store a lawnmower battery for winter?

Remove the battery:

Usually, lawnmowers aren’t used during winter and are held in garages. Most lawnmower owners make one common mistake: not removing the lawnmower’s battery before storing it for the winter season. This may cause your battery to die, so your lawnmower won’t start the next time you want to put it to use.

So, extracting the battery before putting the lawnmower away for winter or an extended period is necessary.

Clean the battery:

The battery must be cleaned using a dry rag and baking soda, charged with a battery charger, and stored in a separate dry place in a cardboard box. This will, for sure, maximize the battery’s life.

Final Remarks:

The battery is a crucial part of a lawnmower, and the lawnmower would be useless to you if the battery doesn’t hold a charge. Therefore, you must find the cause of battery drainage by taking help from this article and remove that problem immediately to make your lawn blooming and more beautiful.

The battery types must be maintained by regularly filling them with distilled water and recharging them. The deep cycle battery shall also be cleaned to clean time and again to prevent corrosion and prolong its life.

• Maintaining the Lawnmower’s Parts

Finally, don’t forget to maintain the lawnmower’s other parts properly, such as filters, cutting blades, and oil. Check the lawnmower engine for any issues. If you find any, you may need to replace certain parts. The muffler, for instance, might need replacement over time.

Also, ensure the voltage regulation functions correctly for the lawn mower’s optimal performance. In case of power issues, the fuse might be the culprit. A blown fuse will disrupt the lawnmower engine’s continual power supply line. If that’s the case, the fuse will need to be replaced.

Lastly, don’t forget the lawnmower engine’s carburetor and other essential parts. Regular maintenance is critical to a long-lasting and efficient lawnmower for lawn care.