Charge your mower battery with the charger that came with it, plugged into a standard outlet, for the time the manual specifies—usually 4 to 24 hours depending on battery type and charger speed

Most modern lawn mowers use either a lithium-ion battery or a lead-acid battery, and each charges differently. Lithium-ion batteries (common on cordless mowers from brands like DeWalt, Makita, and Ryobi) charge faster—often in 30 minutes to 2 hours—and have built-in protection that stops overcharging. Lead-acid batteries (found on riding mowers and some older push mowers) take longer, usually 8 to 24 hours, and need more careful monitoring to avoid damage.

The safest approach is to use only the charger designed for your specific battery. Using the wrong charger can overheat the battery, reduce its lifespan, or create a fire risk. Your mower's manual will list the correct charger model and the recommended charging time.

Key Takeaways

  • Always use the charger that came with your mower or one the manufacturer lists as compatible—mixing chargers and batteries can damage both.
  • Lithium-ion batteries charge in under 2 hours and stop charging automatically; lead-acid batteries take 8 to 24 hours and need you to monitor them.
  • Charge in a dry, well-ventilated space away from flammable materials, and never charge a battery that is visibly cracked, leaking, or swollen.
  • If a battery will not hold a charge after a full cycle, or if the charger gets hot during use, stop charging and contact the mower manufacturer.

Where and how to set up for charging

Charge your battery indoors or in a garage, shed, or covered area where it stays dry. Moisture can damage the charger and create electrical hazards. The space should have good air circulation—do not charge in a sealed closet or inside a plastic storage box.

Keep the battery and charger away from gasoline, paint thinner, propane, or other flammable materials. If you store fuel near your mower, charge the battery in a different room. Never charge a battery in direct sunlight or in temperatures below 32°F or above 104°F; extreme heat or cold slows charging and can damage lithium-ion cells.

Before plugging in, inspect the battery for cracks, leaks, or visible swelling. A swollen battery should not be charged—it is a sign of internal damage. If you see any of these, stop and contact the mower manufacturer or a repair shop.

Charging a lithium-ion battery

Plug the charger into a standard household outlet, then connect the battery to the charger. Most lithium-ion chargers have a light that turns on (usually red or amber) to show charging is happening. When the light turns green or stops blinking, the battery is full.

Lithium-ion batteries have built-in circuits that prevent overcharging, so leaving the battery on the charger after it is full will not damage it. However, for the longest lifespan, remove the battery once it reaches full charge and unplug the charger. If you charge regularly, store the battery at room temperature between uses.

Charging time varies by brand and charger type. A standard charger might take 1 to 2 hours for a full charge, while a fast charger can do it in 30 to 60 minutes. Check your manual for the exact time for your model.

Charging a lead-acid battery

Lead-acid batteries (the type in riding mowers and some older push mowers) need a different approach. Connect the charger's red clamp to the positive terminal (marked with a + sign) and the black clamp to the negative terminal (marked with a − sign). Reverse polarity can damage the charger and battery.

Set the charger to the voltage your battery needs—usually 6, 12, or 24 volts. Your mower manual will specify which. Plug the charger in and let it run for the time listed in the manual, typically 8 to 24 hours for a full charge. Do not leave a lead-acid battery charging unattended for long periods; check on it every few hours to make sure the charger is not getting hot.

If the charger or battery gets hot to the touch, unplug it when ready and let it cool for at least an hour before trying again. Excessive heat is a sign of a problem—either the charger is faulty or the battery is damaged.

Signs a battery needs professional help

If a battery will not charge at all, charges very slowly, or loses its charge within a few minutes of use, it may be at the end of its life. Lithium-ion batteries typically last 3 to 5 years with regular use; lead-acid batteries last 3 to 5 years as well, though this varies by how often you use the mower.

If the charger itself is the problem—if it does not light up, gets hot, or makes a buzzing sound—stop using it and contact the mower manufacturer. A faulty charger can damage a good battery or create a safety risk.

If you are unsure whether the battery or charger is at fault, take both to a mower repair shop or the retailer where you bought the mower. They can test each part separately and tell you which one needs to be replaced.

Storing a charged battery between seasons

If you are storing your mower for the winter or a long period, charge the battery fully before putting it away. Store it in a cool, dry place—ideally between 50°F and 80°F. A basement or garage works well; an unheated shed that freezes in winter does not.

For lithium-ion batteries, check the charge level every month or two during storage. If it has dropped below 50%, charge it again. Letting a lithium-ion battery sit completely empty for months can reduce its ability to hold a charge later.

Lead-acid batteries can sit fully charged for longer periods without harm, but if you store the mower for more than a few months, charge the battery again before using the mower. A battery that has sat unused may need a full charge cycle to perform at its best.

Frequently Asked Questions

Can I use a car battery charger on my mower battery?

No. Car chargers are designed for much larger batteries and deliver power at a rate that can damage a mower battery. Always use the charger made for your mower. If you have lost the original charger, contact the mower manufacturer or a repair shop to find the correct replacement.

How long does a mower battery last before it needs replacing?

Most lithium-ion and lead-acid mower batteries last 3 to 5 years with regular use. Lifespan depends on how often you charge, how deeply you drain the battery before recharging, and storage conditions. Charging in extreme heat or cold shortens battery life.

Is it bad to leave a lithium-ion battery on the charger overnight?

No, it will not damage the battery. Lithium-ion chargers have circuits that stop charging once the battery is full. However, unplugging the charger after the battery reaches full charge is better for long-term lifespan if you charge regularly.

What should I do if my battery swells while charging?

Stop charging when ready and unplug the charger. A swollen battery is damaged and should not be used. Move it to a safe outdoor location away from buildings and contact the mower manufacturer or a repair shop for a replacement.

Can I charge a mower battery in the cold?

Lithium-ion batteries should not be charged below 32°F. Cold slows the charging process and can damage the cells. Wait until the battery and charger warm to room temperature before charging. Lead-acid batteries can charge in cold, but the process will be slower.