How to Charge, Maintain Lawn Mower Batteries

lawn mower battery

A new generation of electric lawn mowers is drawing Americans with the promise of tackling their mowing chores without having to go buy oil and gas, spending the afternoon with ear protection on, swimming in your lawn mower’s exhaust.

Environmental consciousness and advances in electric mower performance are convincing more Americans to buy electric mowers to replace their noisy and pollution-prone gas-powered ancestors.

But with that choice comes the duty of caring for their core component: the battery.

From the newest $100,000 Tesla to the humble golf cart at your local course, the batteries that power them have come a long way, both in power and in the amount of care required.

Here’s what you need to know about properly charging and caring for modern electric lawn mower batteries.

Growth in Electric Mowers

Consumer Reports says previously underpowered electric mowers are now capable of making the cut for most yards, and predicted only to get better. Global sales are expected to top 10 million mowers in 2019, worth around $9 billion. 

And it’s expected to keep growing, as one 2019 market analysis projected an annualized growth rate of 5 percent through 2024. 

The electric mowers will help retire a generation of noisily inefficient gas-powered mowers. The U.S. Environmental Protection Agency says gas-powered lawn and garden equipment can account for as much as 45-percent of nonroad gas emissions.

‘Battery’s the Way to Go’

Jordan Barry, owner of Push Lawn Care in Torrance, Calif., uses electric mowers to cut his clients’ grass every day. 

“Battery’s the way to go. You don’t have to fill it with gas, you don’t have to prime it or warm it up,” he says. 

In nearly six years of daily electric mowing, Barry says problems with batteries and equipment have been nearly nonexistent. 

With the proper care and maintenance, one of those batteries can mow your lawn for years. You’ll never have to go to the gas station, worry about your carburetor or change a spark plug. You won’t wake up the neighbors on Saturday morning or deal with dangerous fumes.  

Here’s how to make that happen.

Mowers’ Batteries Differ

Types of battery-powered, cordless, electric lawn mowers vary at least as much as their gas-powered counterparts. 

From the completely hands-off robotic lawn mowers that criss-cross your yard on their own to riding mowers that can run for hours on a single charge, battery power can do it all around your yard. 

So how do lawn mower batteries differ? Mainly in size, number and charging system.

Walk-behind mowers, which comprise about 80% of the electric mower market, are powered by rechargeable battery packs. Amp settings, run times and charge times can differ, but all battery packs need to be removed from the mower and charged using an approved battery charger.

Riding Mower Batteries

Riding lawn mowers can carry multiple large batteries that stay in place while charging, built more like car batteries than the smaller battery packs that power push mowers. 

For example, the Ryobi RY48110 uses four 12-volt, lead acid batteries connected in a series. 

Charging cordless electric lawn tractors or riding mowers tends to involve specified charger cables or chargers that plug into the wall on one side and into the mower on the other through a built-in charging port in the mower itself.

Sound daunting? At Push Lawn Care, Barry says charging batteries is a cinch. 

Some clients even let them charge batteries while working at their homes, with an average cost to the client of just four cents in electricity. 

The batteries on his mowers give a run time of about 90 minutes, he said, and the charging time is half that.

While one battery operates the mower, another is charging so they can be easily switched out to keep his guys mowing continuously. 

Sometimes, Barry says, he even charges the lawnmower batteries from his car. 

How to Properly Recharge Lawn Mower Batteries

Each battery-powered mower comes with its own charger and instructions on how to get the most out of the battery. 

Lots of advice — some of it conflicting — circulates about whether to leave the battery on the charger all the time, and whether to let the batteries drain completely before recharging.

Gary Koenig
Associate professor Gary Koenig, University of Virginia

For lithium-ion batteries, overcharging and completely discharging them can cut down on the overall life of the battery, says Gary Koenig, associate professor in chemical engineering at the University of Virginia. 

It’s “generally better not to discharge it all the way,” he says. “Don’t run it very low.”

That means keeping the battery’s charge level at 20-percent or better. Discharging it below that will accelerate fade, or the battery’s slow degradation. 

And when recharging, disconnect when it reaches 100-percent. 

Follow Instructions (Which Differ by Manufacturer)

The best thing to do is follow what the manufacturer says in the operator’s manual, Koenig says. 

And manufacturers’ advice differs for different products depending on the specific battery chemistry and use. 

But with recent advances in technology, batteries are lasting longer with less strenuous maintenance from owners. 

Barry says he’s heard similar advice on draining and charging, but says that chargers and batteries these days are smart. He hasn’t seen any negative effects from leaving batteries charging overnight or all weekend.

Manufacturer Ryobi tells customers to unplug chargers and batteries once they’re fully charged, but stops short of warning against leaving them on the charger indefinitely. 

For Ego’s 56-volt rapid charger, the company says a battery left on the charger “will not overcharge.” 

If left on the charger for a month or more, the battery automatically reverts to a 30-percent charge. Just unplug it and plug it back in to start it charging again. 

But in Ryobi’s manual for its line of battery packs, it clearly says to remove the battery pack once fully charged to extend the life of the battery. 

For its electric riding mowers, Ryobi says to simply leave the mower plugged into the charger until you’re ready to use it. 

But either way, Barry says charging mowers is straightforward.

“For the average homeowner, if their battery runs out I’d say go have a drink, come back in 30 minutes and keep mowing,” he says. 

Routine Battery Maintenance Keeps Them Trouble-Free

Whatever their reputation, electric mowers are dependable and essentially maintenance-free. 

Barry says his company regularly leaves mowers in the backs of trucks over the weekend, as long as rain isn’t in the forecast. 

“We have not had a mower fail in five years, almost six years now,” he says. And that’s using these mowers every day in the Los Angeles area where mowing season is all year long. 

During the regular summer mowing season, the average homeowner may cut grass once a week or twice a month.

The big issue is keeping them dry, and keeping mowing decks clean so the motor can run more efficiently and the battery last longer.

And when it comes to batteries, there are some simple maintenance practices that can keep them powering your Saturday lawncare regimen for years to come.

Do’s and Don’ts of Charging a Lawn Mower Battery


  • Do choose batteries and chargers from the original manufacturer, engineered to work the best with the corresponding tool.
  • Do transport and store batteries away from metal objects like keys, coins, screws and nails. The same goes for liquids. These can connect the positive terminal and negative terminal and short the battery out. 
  • Do remove the battery when storing the tool.
  • Do keep the battery dry, clean and free from oil and grease.
  • Do monitor the battery’s performance. Stop use if the battery is overheated, damaged or modified.
  • Do protect the battery terminals. Barry says terminals are the battery’s weak spot, where water, dust and dirt get in. Store batteries where terminals can be protected. 


  • Don’t throw the battery in the trash. Always follow local regulations and recycle the battery at a local recycling center. 
  • Don’t charge the battery in excessively hot or cold temperatures, which Koenig says can also cut into the battery’s useful life. Different manufacturers and products set different temperature limits, found in their owners manuals.
  • Don’t place batteries near fire or heat, including a pilot light, which increases the chance of explosion. 
  • Don’t charge the battery in a damp or wet location.
  • Don’t try to bypass any safety or control devices to change the voltage rate at which a battery charges, Koenig says. 

Sources: Barry, Koenig, the Power Tool Institute, Inc.Ryobi and Ego.

Lawn Mower Battery Life Cycle

Eventually, no matter how well you take care of it, a lawn mower’s battery will lose its effectiveness.

But that may be such a long time that a homeowner need not worry about dead batteries beyond popping them back on the charger.

Most of Barry’s batteries have persisted under years of constant daily use. Only two batteries have given out on him in six years. 

But as he says, “There’s a definite drop off in run time as we’re going forward.”

That’s how you know when a battery is starting to go. If you used to get 90 minutes of mow time from a full charge and now you get 50, get ready to invest in a new battery. 

‘It Won’t Last as Long’

“When it starts to wear out, the biggest thing you’ll see is it won’t last as long,” Koenig says. 

Older batteries become more resistive internally, and have to work harder to complete the same amount of output, he says

Batteries also have some amount of self-discharge, sometimes called “leakage current” or “parasitic current,” Koenig says. 

This means a fully charged battery will slowly drain while off the charger. However, the discharge takes place slowly. It may leak out only a few percentage points per month. So if you’ve left a fully charged battery in the garage over winter, it’s not going dead if it only lasts 50 minutes on that first cut come spring. No trickle charger needed. Just pop the battery back on the charger until it’s fully charged for that first cut of the season. 

Cost of Replacing a Dead Mower Battery

But what if they do die on you? Then it’s time to get another, and the bad news is that the batteries are clearly the most expensive part of cordless push mowers. 

For example, a Ryobi 20-inch 40-volt mower runs $279 at Home Depot. A replacement battery for the same model is $149 at Home Depot.  

The $339 Ego 21-inch 56-volt mower runs on a $250 battery.  

Replacing riding mower batteries or lawn tractor batteries is cheaper, but you may need to buy more of them. 

For the Ryobi RY48110, which costs around $2,500 new, replacing a dead battery will run you about $76. That means all four would be just over $300. 

Even though many models come with several-year warranties, the high cost is all the more reason to make sure you’re taking care of those batteries. 

And Barry admits, it was a high cost upfront, but going from gas power to battery power isn’t a decision he regrets. 

Aside from blade sharpening, replacing the wheels every year or so, and battery charging, the electric mowers are essentially maintenance-free.

“I’m very happy to be running electric,” he says.

Derek Lacey

Derek Lacey

Formerly the agriculture writer for the Hendersonville Times-News, Derek Lacey’s articles have appeared in U.S. News & World Report, The Charlotte Observer, News & Observer, and The State. He has won 15 awards from the North Carolina Press Association and GateHouse Media, for pieces ranging from news features and investigative reporting to photography and multimedia projects.