How To Charge A Lawn Mower Battery?

When you really get down to it, there are a few different types of batteries for lawnmowers. The two most common include the lead-acid batteries in riding lawnmowers and lawn tractors, as well as the lithium-ion batteries that are more common in battery-powered cordless lawnmowers. Even new robotic lawnmowers run on batteries that require some routine care and charging.

How Do Lawn Mower Batteries Work?

Lead-Acid batteries are the traditional batteries that you find in a lot of cars and trucks. They rely on an electro-chemical reaction to hold and discharge direct current. The energy gets depleted, and replenished using n alternator charging unit.In lawnmowers, you are more likely to find them in lawn tractors, riding lawn mowers, and zero-turn riding lawnmowers. They tend to be able to discharge a high amount of cold cranking amps in a short burst, which helps fire up gasoline engines.

Lead-acid batteries are available in a wide range of voltages and sizes. Some are small enough that you can easily hold them in your hand. Though some of the largest lawnmower lead-acid batteries in commercial-grade riding lawnmowers are so large that an average person can barely lift them.

How Long Should The Battery Charge For?

Most lawn mower batteries charge at 10amps for an hour.

What Type Of Charger Should I Use?

These days most of the lead-acid lawnmower batteries you find in a riding lawnmower or lawn tractor are 12-volts. Though there are some chargers that have 6-Volt and 12-Volt charging settings for times when you might need to charge a smaller battery. If you have a charger like this, you will want to make sure it’s set to 12-Volts.

You also want to consider the Amperage rating of the battery charger. Ideally, you want to use a charger with an output of 10-Amps or less. There are some commercial-grade battery chargers that are sold at the consumer level that have more than a 10 Amp output. These could potentially damage your smaller lawnmower battery.

Ideally, you want a “Smart Charger.” This is a special type of battery charger with sophisticated monitoring settings that actively read the charge level of the battery. When it gets to the maximum charge, the Smart Charger reduces the flow of current to maintain the battery at 95 to 98% capacity. This prevents overcharging.

What Happens If I Over Charge A Lead Acid Battery?

Lead-acid batteries rely on electrochemical reactions to help store charge. The heat and excess current of over-charging can cause serious damage to a lead-acid battery in both the short and long-term. Left unchecked for long enough it can potentially cause a failure in the battery’s seals which could leak dangerous acid out.

If you don’t have a “Smart” battery charger, you want to keep an eye on the charger’s display. A few hours of over-charging isn’t a big deal, but you don’t want to let a lead-acid battery sit on a charger at maximum charge for more than say a single overnight.

How To Charge A Lead Acid Battery For A Riding Lawnmower

With the right charger in hand, you can then follow these steps to properly charge your lead-acid lawnmower battery.

  1. Take all the necessary safety precautions. This includes putting on protective clothing, gloves, and most importantly safety glasses.
  2. Check the battery connections for signs of corrosion. Some lead-acid batteries can develop white or bluish-green corrosion on the battery posts. Sometimes it can buildup so much that it prevents the battery from taking a charge. If you do see signs of corrosion, you will want to use the battery cleaning steps later in this article.
  3. Make sure the battery charger isn’t plugged into the electrical outlet.
  4. Connect the red positive line of the charger to the red positive terminal on the lawnmower battery.
  5. Connect the negative, black line of the charger to the negative black terminal of the lawnmower battery.
  6. Double-check to make sure that the charger is on the 12-volt setting.
  7. Plug the battery charger into the nearest electrical outlet.
  8. Look at the display on the battery charger to make sure it isn’t showing any faults. A lot of battery chargers will also make a gentle, high-pitched hum which tells you it’s producing charge for the battery.

How Long Does It Take To Charge The Battery?

Assuming you have a 10 Amp charger connected to a 12-Volt battery the average riding lawnmower battery should be fully charged in about an hour to an hour and a half. If it takes more than 2 hours, you should be suspicious of a problem with either the battery, the charger, or perhaps corrosion on the positive battery terminal. After the battery is fully charged, turn off the switch and unplug the unit. Wait a few minutes in case any gasses accumulated around the battery. Then unclamp the negative and positive cables.

How Do I Clean Corrosion Off A Battery Terminal?

Corrosion on the positive battery terminal can prevent a lawnmower battery from receiving a charge. It usually looks like white powder, though it may also have a blue-ish green or gray tinge, depending on the type of connecting hardware.

It doesn’t necessarily mean that your lawnmower battery is shot. However, it will make it difficult to properly charge the battery. Thankfully it’s easy to clean off using the following steps.

  1. Put on protective clothing, especially gloves and protective eyewear.
  2. Mix together baking soda and distilled water in a 1:1 ratio. Stir until it turns into a paste.
  3. Carefully disconnect both battery terminals. Disconnect the red before the black.
  4. Use an old toothbrush to gently scrub off any corrosion from both the positive battery terminal as well as the connection hardware.
  5. Wipe clean with a dry paper towel.
  6. Carefully check to make sure all signs of corrosion have been cleared away from the battery terminal and the connecting hardware. If you see any lingering corrosion, repeat step 4.
  7. Let everything dry for a solid 15 to 20 minutes, and wipe down again with a clean paper towel.
  8. Carefully reconnect the lines to the battery terminals, and firmly tighten down the hardware.

At this point, you can test the lawnmower battery or connect it to your 10 Amp, battery charger on the 12 Volt setting

How Much Does A Dead Mower Battery Cost?

It depends, however a new battery does not come cheap. I can be one of the most expensive replacement parts. Typically a new mower battery can be anywhere from $79 to as much $300.





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