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Cordless mower battery not charging

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In short

Most cordless mower batteries that refuse to charge are too hot or too cold, have been run or stored completely flat, or are not making clean contact with the charger. Let the pack reach room temperature, clean the contacts, try a different socket and check the charger lights against your manual. If a known good charger still rejects the pack, it is likely worn or faulty and should be replaced.

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A battery that will not charge usually shows up at the worst moment: grass long, weekend sunny, mower dead. The good news is that many charging faults come down to temperature, dirt or a pack that has fallen too low, and these are easy to check at home. This guide works through the causes in order, from simple to serious, and explains when to stop and replace the pack. Charger light patterns differ between makers, so keep your manual to hand while you work.

Quick checks before anything else

Start with the boring things. A surprising number of charging faults are a switched off socket, a loose plug or a pack that is not fully seated in the charger.

  1. 1

    Plug the charger into a different wall socket you know works, not an extension reel left outside.

  2. 2

    Remove the pack and reseat it firmly until it clicks into the charger.

  3. 3

    Watch the charger lights and compare them with the table in your manual.

  4. 4

    Feel the pack. If it is hot from mowing or cold from the shed, set it aside to reach room temperature.

  5. 5

    If you own a second pack from the same range, try it in the charger to see whether the fault follows the pack or the charger.

Temperature lockouts: too hot or too cold

Lithium-ion packs and chargers include protection that blocks charging outside a safe temperature range. A pack straight off a mower on a warm day can be too hot to charge, and a pack brought in from a frosty shed can be too cold. Many chargers show a distinct light or simply wait until the pack is within range.

Leave the pack indoors at normal room temperature for an hour or so, away from radiators and direct sun, then try again. Do not speed things up with a heater or by putting it in the fridge. Your manual gives the charging temperature range for your model.

Deep discharge after storage

A lithium pack left flat for months, often over winter, can drop below the voltage its protection circuit will accept. The charger then treats it as faulty. Some chargers try a slow recovery charge first; others refuse outright. The behaviour is brand-specific, so check the manual or the maker's support pages rather than trying workarounds.

Never try to jump start a deeply discharged pack from another battery or a car charger. That bypasses the protection built in for a reason. If the maker's charger will not take it, the pack needs replacing. To avoid this next year, follow our guide to storing mower batteries over winter.

Dirty or damaged contacts

Grass clippings, dust and damp can coat the metal terminals on the pack and charger. With the charger unplugged, look into both. Brush out debris with a dry soft brush and wipe the terminals with a dry cloth. Do not use water, metal tools or sprays inside the terminals.

If a terminal is bent, scorched or corroded green, stop. That points to a fault that home cleaning will not fix, and the pack or charger should go to the maker or a dealer for assessment.

Reading the signs: pack or charger?

Light patterns and error codes vary between brands such as EGO, Ryobi, Greenworks and Bosch, and between charger models within a brand. The table below covers general patterns only; your manual has the exact meaning for your charger.

What you seeLikely causeWhat to do
No lights at allNo power to charger, or charger faultTry another socket; test with a second pack
Lights show waiting or temperaturePack too hot or too coldRest at room temperature, then retry
Fault or error light with one pack onlyPack worn, deeply discharged or damagedContact the maker or replace the pack
Fault light with every packCharger faultContact the maker about a replacement charger
Charges but runs for minutesPack at end of lifeReplace the pack and recycle the old one
General patterns, confirm in your manual

Note:Lithium batteries: use only the maker's charger for your pack, do not charge or use a pack that is swollen, cracked, leaking or has been dropped hard, and store packs away from heat, direct sun and frost. Take worn or damaged batteries to a proper battery recycling point, never household waste.

When to replace the battery

Lithium packs lose capacity with age and charge cycles. If a pack charges but runs for a fraction of its old time, or the charger rejects it after you have ruled out temperature, dirt and the socket, replacement is the safe answer. Buy the maker's own pack in the same voltage family. Our cordless lawn mower guide lists which battery comes with each mower, and mower battery voltage explained covers how to compare packs.

If your mower and charger are still in warranty, contact the maker before you buy anything. Keep the receipt and note the model and serial numbers.

Frequently asked questions

Why is my mower battery charger flashing? A flashing light usually means waiting, a temperature hold or a fault, but each maker uses its own pattern. Check the light table in your charger's manual or on the maker's website.

Can I leave a mower battery on the charger? Many modern chargers stop when the pack is full, but makers differ in their advice. Follow the manual, and do not leave packs charging unattended in a hot shed or near anything flammable.

How long should a mower battery take to charge? It depends on the pack size and the charger. A fast charger fills a pack much sooner than a standard one. The listing or manual states the charge time for your pack and charger pairing.

Is it safe to keep using a swollen battery? No. Stop using it, do not charge it, store it outside the house away from anything flammable and take it to a battery recycling point. Never put it in household waste.

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