Maintenance Advice · Updated June 2026
Cordless Mower Battery Care & Runtime
The battery is the most expensive part of a cordless mower, often a third to a half of the price. Look after it and it will outlast the warranty. Neglect it and you will be buying a replacement long before you should. Here is how to get the most from it.
Looking after a lithium-ion battery
Every modern cordless mower runs on lithium-ion cells, the same chemistry as a phone or a cordless drill. They are reliable and need no real maintenance, but a few habits make a big difference to how long they last.
- Store partly charged. The ideal storage charge is around 40-60%. A lithium-ion cell ages fastest when sat at a full 100% or left at empty for long periods.
- Avoid deep discharge. Don't run the battery completely flat as a habit. Recharge when it gets low rather than squeezing out the last second of every mow.
- Keep it cool and dry. Heat is the enemy of battery life. Don't leave a pack baking in a sunny car or store it in a damp, freezing shed. A cool indoor cupboard is ideal.
- Don't leave it on the charger long-term. Charge it shortly before you need it, then unplug. Sitting at 100% for weeks shortens its life.
- Let a hot battery cool before charging. After a long mow on a warm day, give the pack 20-30 minutes before putting it on charge.
Winter storage
Over the off-season, take the battery out of the mower and store it indoors at about 50% charge, somewhere that stays above freezing, a hallway cupboard or heated garage, not an unheated shed. Check it every couple of months and top it up to around 50% if it has drifted low. Come spring, a fully charged pack will be ready to go and none the worse for the break.
How to get more runtime from a charge
Runtime complaints are nearly always about how the lawn is mown, not a faulty battery. These five steps stretch a single charge much further.
- Sharpen the blade. A blunt blade forces the motor to work far harder, draining the battery fast. A sharp blade is the single biggest runtime win, it cuts with less effort and less current draw.
- Mow dry grass. Wet grass is heavier and stickier, loading the motor and cutting runtime noticeably. Wait for the lawn to dry whenever you can.
- Raise the cut height. Taking less off in each pass means less resistance and less power used. Drop the height for a final tidy-up pass only if needed.
- Mow little and often. Short, regular cuts move through grass quickly. Letting the lawn grow long means slow, power-hungry passes and far less area per charge.
- Keep the deck clean. Caked clippings under the deck add drag and disrupt airflow, making the motor work harder. Scrape it clean after each mow.
Of these, a sharp blade makes the biggest single difference, a blunt blade can cut effective runtime by a third or more because the motor is fighting the grass rather than slicing it.
Understanding Ah (and how it sets runtime)
Two numbers on a mower battery decide everything: voltage and amp-hours.
- Voltage (V), how much power and torque the motor can deliver. Higher voltage cuts long, wet grass without stalling.
- Amp-hours (Ah), how much energy the pack stores, and therefore how long it runs. A 5.0 Ah battery lasts roughly twice as long as a 2.5 Ah one on the same mower.
As a rough guide, a typical 36-40 V mower covers around 100-150 m² per Ah on dry grass, so a 4.0 Ah pack might cover 400-600 m² on a charge. Wet or long grass, a blunt blade or a low cut height will all pull that figure down. If you regularly run out before finishing, a higher-Ah battery (or a spare to swap in) is usually the answer rather than a whole new mower.
Battery lifespan and when to replace
A quality lithium-ion pack from a reputable brand is rated for roughly 500 to 1000 charge cycles. For someone mowing 25-30 times a season that works out to about 5 to 8 years of normal use. Cheaper cells in budget mowers often manage only 2 to 3 seasons before noticeably fading.
Capacity falls gradually rather than all at once. The signs it is on the way out:
- Runtime has roughly halved from when it was new, despite a sharp blade and dry grass.
- It charges much faster than it used to, a sign it is holding far less energy.
- It struggles or cuts out under load in grass it used to handle easily.
- The pack gets unusually hot in normal use.
When you do replace it, buy a genuine pack from the same battery platform. A big advantage of the mainstream systems, Bosch Power for All, Ryobi ONE+, EGO, Makita and so on, is that the replacement battery also fits your other garden and power tools, so it is rarely money wasted.
Choosing your first cordless mower, or weighing a battery one against petrol? See the best battery-powered mower reviews and our cordless vs petrol vs electric guide.