# Cordless mower not working or cutting out

Source: https://mowandedge.co.uk/blog/cordless-mower-not-working
Published: 2026-10-12
Publisher: Mow and Edge

**In short:** Most cordless mowers that will not start have a simple cause: a flat or badly seated battery, a missing safety key, the wrong start sequence on the bail bar, or a deck clogged with wet grass. If the mower starts but cuts out, it is usually an overload or heat cut-out, so raise the cutting height, clear the deck and let the battery cool.

A battery mower that refuses to start is frustrating, but it rarely means a broken motor. Cordless mowers have several safety interlocks and protection circuits, and any one of them will stop the motor. Work through the checks below in order, from the quickest to the most involved. Always make the mower safe first by removing the battery and safety key before you look underneath.

## Make the mower safe first

Before any check that involves the deck or blade, remove the battery and the safety key if your mower has one, and wait for the blade to stop. Put on gloves. Only refit the battery when you are standing behind the handle, ready to test.

Note: Remove the battery or safety key before you touch the blade, clear the deck or tip the mower, and wait for the blade to stop completely. Wear sturdy gloves, as the blade edge stays sharp. Never tip or lift a running mower. Charge batteries only with the maker's charger, away from heat, and stop using any pack that is swollen, cracked or very hot. If in doubt, ask a dealer or service agent.

## Mower will not start: quick checks

Start with the battery. Check the charge indicator on the pack or charger, and recharge if it is low. Push the battery fully home until it clicks; a pack that is not fully seated may not make contact. Look at the contacts for dirt or grass and wipe them with a dry cloth.

Next, the safety key. Many cordless mowers have a removable key or a key button that must be fitted or pressed before the motor will run. Some designs need the battery cover closed or the grass box or mulch plug fitted. Check your manual for the exact interlocks on your model.

1. Charge the battery and check its indicator.
2. Remove and refit the battery until it clicks into place.
3. Fit the safety key or press the key button.
4. Close the battery cover and fit the grass box or mulch plug if required.
5. Check the handle is fully unfolded and locked.
6. Follow the start sequence in the manual: usually press the safety button, then pull the bail bar.

## Bail bar and start sequence

Most mowers need a two step start: hold a safety button or lock, then pull the bail bar (the lever on the handle) against the grip. If you pull the bar first, or release the button too soon, the motor will not run. The order varies between brands, so check the manual.

If the bail bar feels loose or does not move freely, the cable or switch linkage may be damaged or caught. Do not force it or bypass it, because it is a safety control that stops the blade when you let go. A dealer or service agent can replace a damaged switch or cable.

## Mower starts then cuts out

Battery mowers protect their motors and packs. If the load is too high, as in long, thick or wet grass, the electronics cut the power. If the battery or motor gets too hot, a thermal cut-out does the same. On many mowers, a flashing light on the battery or handle indicates which protection has tripped; the manual explains the codes.

Raise the cutting height, slow your walking pace and take narrower passes. Follow the RHS one-third rule and do not remove more than a third of the height at once; our [one-third rule tool](https://mowandedge.co.uk/tools/one-third-rule) shows the steps. If the battery feels warm, let it cool in the shade before carrying on or recharging.

| Symptom | Likely cause | What to try |
| --- | --- | --- |
| Stops in long or wet grass | Overload cut-out | Raise height, slow down, cut in stages |
| Stops after a long run on a hot day | Thermal cut-out | Let battery and motor cool |
| Stops soon after a full charge | Ageing or cold battery | Warm to room temperature, try a second pack |
| Runs but labours and leaves grass uncut | Clogged deck or blunt blade | Clear deck, sharpen or replace blade |
| Hums but blade does not turn | Blade jammed | Remove battery, clear the jam |

Cut-out symptoms and likely causes

## Clogged deck, jammed or blunt blade

Wet clippings build up under the deck and around the blade, adding drag until the overload protection trips. With the battery and key removed and gloves on, tip the mower as the manual allows and scrape out the build up with a plastic scraper or stick. Check nothing such as a twig, stone or string is wrapped round the blade.

A blunt or bent blade makes the motor work harder and tears grass. Our guide on [sharpening or replacing mower blades](https://mowandedge.co.uk/blog/how-to-sharpen-or-replace-mower-blades) explains the basics; follow your manual for blade bolt torque and orientation.

## Battery and charger problems

If the battery will not take a charge, try it on a second charger or try a different battery in the mower to isolate the fault. Packs left completely flat for months, or stored in a frozen shed, may refuse to charge. Our article on a [cordless mower battery not charging](https://mowandedge.co.uk/blog/cordless-mower-battery-not-charging) covers the charger lights and checks in more detail.

If nothing works, contact the maker or a dealer, especially while the mower is under warranty. If the mower is old or the battery is worn, compare replacements in our [best cordless lawn mower guide](https://mowandedge.co.uk/best/best-cordless-lawn-mower).

[Compare cordless lawn mowers](https://mowandedge.co.uk/best/best-cordless-lawn-mower)

## Frequently asked questions

**Why won't my electric lawn mower start?** The most common causes are a flat or loose battery, a missing safety key, or the wrong start sequence on the bail bar. Check each in turn.

**Why does my cordless mower keep cutting out?** Usually an overload or heat cut-out from long or wet grass, or a clogged deck. Raise the cutting height, clear the deck and let the battery cool.

**Can a cold battery stop a mower working?** Yes. Lithium packs work poorly when very cold. Bring the battery indoors to room temperature before charging or using it.

**When should I take it to a dealer?** If the bail bar or switch is damaged, the motor hums but will not turn with a clear blade, or the battery is swollen or damaged, stop using it and contact a dealer or the maker.

## Buying guides on this topic

- https://mowandedge.co.uk/best/best-cordless-lawn-mower
- https://mowandedge.co.uk/best/best-cordless-mower-for-small-garden

## Sources

- [RHS: lawns](https://www.rhs.org.uk/lawns)