How long does a cordless mower battery last?

Run time per charge: start with watt hours

Voltage and amp hours each tell only part of the story. Multiply them and you get watt hours (Wh), the energy in the pack. An 18 V 5 Ah battery holds about 90 Wh; a 40 V 2.5 Ah battery about 100 Wh; a 56 V 5 Ah battery about 280 Wh. More watt hours means more mowing, all else being equal.

Makers quote run time or lawn area based on good conditions. Listings in our guides give a feel: the Yard Force 40 V 37 cm lists an average battery life of 40 minutes on a 2.5 Ah pack; the Greenworks 40 V 41 cm is listed for about 250 m² per 2 Ah battery; the Greenworks 60 V self drive mower with two 4 Ah packs is listed at 45 minutes; and EGO quotes up to 45 minutes for its ST1510T strimmer on a 56 V 2.5 Ah battery.

What shortens run time

Anything that makes the motor work harder drains the battery faster. Long grass, wet grass, a low cutting height, a blunt blade and a deck clogged with clippings all add load. Mulching uses a little more energy than collecting, and self drive uses some energy for the wheels. Cold batteries also give less, so a pack straight from a cold shed will not deliver its full rating.

To get the most from each charge, mow dry grass, keep the blade sharp, clear the deck, and follow the RHS one-third rule: never remove more than a third of the grass height at once. Our one-third rule tool works out the steps from long grass.

• Long or wet grass increases load.
• Low cutting height means more grass to cut.
• A blunt blade or clogged deck adds drag.
• Cold batteries deliver less energy.
• Mulching and self drive use a little extra.

How many seasons a battery lasts

Lithium-ion batteries wear gradually with charge cycles and age. Instead of failing suddenly, they hold a little less each year, so a pack that once finished the lawn may eventually need a top up halfway. How fast this happens depends on how often you use it, how hot it gets and how it is stored.

Warranties give a hint of what makers expect. The Greenworks 48 V and 24 V kits in our guides list a 2 year battery warranty, and the Greenworks 60 V self drive listing mentions a 4 year battery warranty. With sensible care, many packs last well beyond their warranty, but treat a battery as a part that will eventually need replacing.

How to make a mower battery last longer

Most makers give similar advice, though you should follow your own manual. Avoid leaving the pack fully flat for long periods. Let a hot battery cool before charging. Charge at room temperature, away from direct sun and heat. Over winter, store packs indoors in a cool, dry, frost free place, often at part charge; our guide to storing mower batteries over winter covers this.

1. 1

   Charge with the maker's charger only.

2. 2

   Let the battery cool after mowing before charging.

3. 3

   Do not leave packs in a hot car or a freezing shed.

4. 4

   Store indoors over winter at the charge level the manual suggests.

5. 5

   Check packs for damage before each season.

Note:Stop using any battery that is swollen, cracked, leaking, very hot or smells of burning, and do not try to open or repair it. Take damaged packs to a household waste recycling centre that accepts batteries, never in household rubbish. Remove the battery or safety key before touching the blade or clearing the deck, and wear gloves.

When one battery is not enough

If a full charge does not finish your lawn, you have three options: a larger capacity pack, a second battery to swap in, or a mower with more watt hours as standard. Some kits come with two batteries, such as the Greenworks 40 V 41 cm and Makita DLM462PT4, which includes four 5 Ah packs for large lawns.

Measure your lawn with the lawn area calculator and compare it with the rated area. Our large garden cordless mower guide and best cordless lawn mower guide list kits by battery and rated area.

Mowers for larger lawns →

Frequently asked questions

How long does a lawn mower battery last on one charge? Typically 20 to 60 minutes, depending on watt hours, the mower and the grass. Check the maker's rated area for a better guide.

How long does an EGO mower battery last? It depends on the pack size. EGO quotes up to 45 minutes for its ST1510T strimmer on a 56 V 2.5 Ah battery; larger packs run longer. Check EGO's figures for your mower and battery.

How many years does a cordless mower battery last? Usually several seasons with good care, gradually holding less charge. Storage, heat and use all affect it.

Can I leave the battery on charge? Many chargers stop when the pack is full, but makers often advise removing it once charged. Follow your manual.