How to Charge Your Lawn Mower Battery, Power Tools and More (2024)

Behind every healthy lawn is a healthy lawn mower battery.

Actually, every house project relies on batteries. The drill you used to hang the TV runs on a battery. So does your cordless sander. Batteries take your tools farther than any cord, as long as they're healthy.

Here's how to get more life out of your batteries.

Why you should charge your lawn mower battery before spring

You can get years more out of your lawn mower battery, if you follow two simple steps:

• Keep it out of the heat.
• Keep it charged.

Your riding lawn mower comes with the same essential parts a car has. It has an internal combustion chamber, an alternator, a 12-volt lead-acid battery, etc. A riding lawn mower with an especially small engine may have a 6-volt battery. The lawn mower's alternator keeps its battery charged. A few hours of mowing recharges it the same way hours of highway driving can keep your car battery mostly charged.

You might not mow the lawn in winter.

That means your lawn mower battery may be totally drained.

Lead-acid batteries drain themselves when they're not used. That's bad news. They need to stay chargedor they'll lose the ability to hold electricity. You can try to charge them if that happens. Still, they may be too weak to start an engine.

Lithium-ion batteries drain themselves, too, when they're not in use, just not as quickly. Keeping your rechargeable lawn mower fully charged for months isn't healthy for the lithium-ion batteryinside. Letting it drain to zero percent damages it, too.

Whether your lawn mower uses a lithium-ion battery or a lead-acid battery, charge it in January or February. Charging your lawn mower battery keeps it healthy for years.

Before you charge:

• Leave the battery in the mower. You don't have to uninstall the battery to charge it.
• Clean the terminals. Use baking soda and a dry cloth.
• Check the voltage and amp settings. Your battery's label will say if it's lithium-ion or if it contains lead. You'll also see if it's 12 volts or 6 volts. Set the charging amps to less than 2 amps if the charger has the settings for it. Charge slowlyto protect the battery.
• Follow the charger's instructions. The manual gives you any other steps your charger needs.
• Last-minute safety check. Take off jewelry. Put on gloves and safety glasses. Make sure there's decent airflow around you.

5 steps to charge your lawn mower battery

1. Connect the charger to the battery. Positive first. Then negative. Positive is usually in red, but always check the symbols on your equipment.
2. Plug the charger into a power outlet.
3. Adjust the settings and let it charge. Usually you'll use a 12-volt charger for your mower, but some lawn mowers use 6-volt batteries, so check the label first. Match the charger's voltage setting to the battery and use fewer than 10 amps.
4. Monitor the charger until it's done. Check your charger regularly to avoid overcharging or overheatingthe battery. The charger may turn off automatically or switch to a float charge. Otherwise, unplug it if it's done charging.
5. Unplug the charger when it's done. Then disconnect the cables, negative before positive, in the opposite order as before.

A trickle charger makes it easy to keep your lawn mower battery ready. It charges lead-acid batteries for days at a time to protect the battery's lifespan. You could leave your lead-acid lawn mower battery on the charger all winter long if it has a float setting. The charger will top off its charge for months and keep it from losing power while it sits on the shelf.

A smart charger will recharge a lawn mower battery in hours. Adjust the voltage and amp settings if you're charging a 6-volt lawn mower battery instead of a 12-volt one.

Want to protect your lead-acid lawn mower battery? Keep it 100 percent charged.

Want to protect your lithium-ion lawn mower battery? Leave it 70 percent to 80 percent charged while in storage. Being fully charged or totally depleted hurts lithium-ion batteries. Check the manual for charging instructions.

The nice part is you can just recharge your lithium-ion lawn mower if it doesn't start. You'll never need to jump-start a riding lawn mower with a lithium-ion battery.

Now, you can jump a lawn mower if it has a lead-acid battery. Here's how.

How you can safely jump-start your lawn mower battery with your car

You can jump your lawn mower with your car. It's the same steps as a regular jump-start— with three big differences.

1. Turn off the car before connecting cables to your lawn mower. The car's alternator generates too many amps and can damage the mower's parts, including the battery. Never jump-start a lawn mower battery from a running car. Don't even leave the key in the ignition.
2. Protect the positive cable from touching anything but the battery terminals in the car and mower. The positive cable is usually the red one. You'll connect it first to the mower, then the car. Otherwise you could damage your car battery.
3. Run the mower for at least two hours after disconnecting the cables. John Deere, Ryobi, Cub Cadet — all gas-powered riding lawn mowers have an alternator. Mowing will charge their starting battery.

Jump-starting should be the last resort. Wait if you can. Connect your lawn mower's battery to a charger. Then do a different home project with your other power tools.

Time to talk about your other power tools.

Tips to make your power tool battery last longer

Take care of your power tool batteries, and your tools will be ready any time you need them.

Power tools run on three different types of batteries:

• Nickel cadmium or NiCd batteries
• Nickel-metal hydride or NiMH batteries
• Lithium-based, including lithium-ion or lithium-polymer batteries

Now, each battery type needs different care. It's easy to assume one tip for one battery type will work for all batteries. The truth is each battery type needs something different.

You might be reaching for a screwdriver sooner than you expect if you give your cordless drill the wrong kind of TLC.

The right way to care for your NiCd battery

A NiCd battery needs to be run hard. Charge it up and drain it to zero percent every month or two. Then store your NiCd battery when it's fully drained.

NiCd batteries are one of the few types that like being stored on empty. They also drain themselves quickly when they're not in use. Don't bother recharging it if you only used it for two minutes.

Fast charging doesn't stress a NiCd battery. So put it on the charger right before you run your leaf blower or cordless sander. Then use every bit of energy before putting it back.

Sitting on a charger can damage a NiCd battery. Its insides can crystalize and resist turning back into electricity. That might be why your NiCd battery doesn't last as long as it used to. A pulse charger can heal your NiCd batteries if you've kept it charged too long. You might not get the battery back to perfect health, though.

Instead, keep fast-charging your NiCd battery and draining it to zero.

Exercising it protects the material and gives your cordless power tool batteries a much longer lifespan.

The right way to care for your NiMH battery

A NiMH battery needs to stay out of the heat, to charge with its original charger and to be drained to zero percent every few months.

If you're using your power drill for a few hours every day, a NiMH battery is perfect. NiMH batteries are handy for power tools. They weigh less, carry more power and last longer between charges than a NiCd battery.

They don't do well in storage. NiMH batteries will drain themselves. It's not as quick as a NiCd battery. All the same, you'll want to use your NiMH-powered drill every other day to get the most life from the battery.

Recharging NiMH batteries uses a special algorithm. Don't use a NiCd charger on a NiMH battery. It can hurt the battery's lifespan if not overcharge it. Keep the charger that came with the power tool. You can replace it, but make sure it's specifically made for NiMH batteries.

NiMH batteries struggle with heat. That's a problem because a NiMH battery will heat up as it runs power or charges. Be gentle with it. Take it off the charger early if the case feels warm. Also, let it cool down before you recharge after it charges.

You can expect a long, full life out of your NiMH battery by keeping it in use and near its original charger.

The right way to care for your Li-ion battery

Lithium-ion batteries weigh the least and offer the longest life overall, but they're sensitive to getting dropped, overheated or overcharged. How you protect your phone batterywould work on your lithium-ion power drill:

• Keep it away from heat.
• Don't leave it on the charger.
• Don't let it ever run down to zero percent.

Store a li-ion battery at 80 percent power, not 100 percent. This battery type doesn't drain itself that quickly. It'll hold charge for weeks.

The way to take care of your lithium-ion battery is to charge it before it drops to 20 percent. Keep it charged between 40 percent and 80 percent. You can top it up to 100 percent before you sand the deck or trim the hedges. Just don't leave it fully charged.

Staying at 100 percent corrodes the active materials, which means the battery can't hold as much electricity as before. The same happens if it ever drains to zero, but faster. Check the power level while you work. Stop and recharge it if you're close to 25 percent left.

Take care of your lithium-ion battery, and it'll keep powering on.

Leaving your power tools on the charger does not help the battery.

Trying to charge a battery that's already full can damage it. Most battery chargers will stop charging if the battery is full.

The built-in protection means it should be safe to leave it on the charger, right? Not quite.

Only lead-acid batteries like to stay fully charged. The other battery types need exercise. They'll drain themselves, even if sitting on a shelf. That's okay, depending on the battery type. All battery types need exercise. Leaving them on the charger robs batteries of that exercise.

A battery on the charger will go through short run-and-recharge cycles. It'll drain to 99 percent, recharge, drain again and recharge again. Those short cycles hurt most batteries. Instead, your power tool batteries need to keep the electrons flowing.

Consider it another good reason to do those house projects today.