If you depend on a riding lawn mower to cut your grass, you know how disruptive it can be when your battery dies. If you need to check your lawn mower's battery, you can use a multimeter. A multimeter is also useful to discern the health of your battery. Knowing how to do some basic testing and maintenance with a multimeter can help you save time when your battery starts to get old.
Riding Lawn Mower Batteries
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While riding lawn tractors run on a gas engine, most have a battery that's equipped to start the tractor's combustion engine. The batteries also often power other incidentals on the mower, like lights or power steering.
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These batteries recharge while you're moving. They use some of the energy that's produced by the gas engine to keep the battery topped off. Most riding lawn mowers are equipped with 12V batteries, although smaller models may have 6V batteries. These batteries usually last for two to three years, so if you're approaching that mark, your battery may not be able to hold a full charge.
Signs a Lawn Mower Battery Is Failing
There are a couple of signs that may give you some warning that your battery is about to die. If you're having trouble getting the engine to catch when you turn the key or you hear groaning and clicking when trying to start the engine, that's a sign that the charge on your battery may be low. Likewise, if any of the electronics on the mower aren't working correctly, the battery may not be able to hold enough charge to run things properly while you mow.
However, the biggest sign of a failing lawn mower battery is if your battery starts to drain faster than usual. This means that it can't hold as much of a charge. In fact, one of the first ways you can check to see how your lawn mower's battery is doing is to connect it to a lawn mower battery charger when it gets low. Leave it on the charger for about eight hours.
If the battery still reads as dead or low or is still charging, then you should probably begin to look for a replacement. If the battery does fully charge and can maintain that charge, then your problem may actually be with the alternator rather than with the battery itself.
Check a Lawn Mower Battery With a Multimeter
The easiest way to check how well your battery is holding a charge is to test it directly using a multimeter. A multimeter can measure a number of electrical properties and will be able to immediately tell you how much charge is left in your battery. These batteries are direct current (DC), so set the multimeter to read DC. Some models have 12V and 6V settings, so choose the appropriate setting.
Access the battery and remove it from the tractor if necessary. Check the lawn mower battery posts for any corrosion, buildup or debris, as this can affect the transfer of energy. You'll want to clean them off using a flathead screwdriver or an appropriate wipe before testing the battery. While cleaning, note which post is positive and which is negative. Industry standard usually marks the positive terminal in red and the negative terminal in black.
To test the voltage, connect the red lead from the multimeter to the positive terminal and the black lead to the negative terminal. The multimeter will then produce a reading – this value should be at or above the nominal voltage of the battery. For example, a 12V battery might read as 12.3 or 12.7, whereas a 6V battery might read 6.6. These are all healthy, fully charged batteries. However, if the reading is less than the nominal battery value (11.5V or lower for a 12V battery), you will need to replace the battery.