Graham FisherBy Graham Fisher

Updated November 2026

A Black and Decker battery lawn mower that won’t start usually comes down to one of a few causes: a battery that isn’t fully seated or charged, a safety key or handle lock that isn’t engaged, or a dirty contact. This guide walks you through the checks in the order that solves the most problems fastest, so you can get back to mowing without guessing.

Check the Battery and Charge Level

Start with the battery, since most no-start complaints trace back to it. Remove the battery pack and look at its charge indicator. Many Black and Decker packs have a small row of LEDs or a button you press to see the level. If the lights are off or only one flashes, put the battery on the charger and let it charge completely before testing again.

Shopping for one? See our guide: 3 Best Black and Decker 13 Amp Lawn Mower Won't Starts (2026): Our Picks.

Next, reseat the battery. Slide it out, check the rails for debris, and push it back in until it clicks. A pack that sits even slightly high will often fail to make full contact.

Verify the Safety Key and Handle Bar

Most Black and Decker battery mowers use a safety mechanism that prevents starting unless the handle bar is held down and the mower is in the correct position. Press the start lever firmly and hold it while you press the start button or switch. If the mower has a removable safety key, make sure it is fully inserted. A key that is loose or partly out will block the circuit even when everything else is fine.

Inspect the Connections and Contacts

If the battery is charged and the safety features are engaged, look at the electrical contacts. Check the terminals on the battery pack and the matching contacts inside the mower deck housing. Look for corrosion, grass clippings packed into the slot, or a bent pin. Remove debris with a dry cloth or a soft brush. Do not use water or solvent on the contacts.

Quick Checklist

  1. Charge the battery fully and confirm the indicator shows a full level.
  2. Remove and reinsert the battery until it clicks into place.
  3. Insert the safety key fully, if your model uses one.
  4. Hold the handle bar down while pressing the start control.
  5. Clean the battery terminals and mower contacts with a dry brush.
  6. Try a different charged battery, if you have one, to rule out the pack.

Test the Mower and Rule Out Other Causes

If the mower still won’t start after the steps above, swap in a known-good, fully charged battery. If the mower runs with the second pack, the original battery has failed and should be replaced. If it still does nothing, the problem is more likely in the mower itself, such as a faulty switch, a blown fuse or a wiring fault. At that point, a repair shop or Black and Decker’s authorized service center can test the electrical system properly. Check the official Black and Decker site for service options and current warranty terms.

For a broader comparison of likely causes, see Black and Decker Cordless Lawn Mower Won't Start: 7 Fixes to Try or Battery Powered Lawn Mower Won't Start: 8 Causes and Fixes.

Common Mistakes

  • Assuming a battery is charged because the charger light came on. Wait for the pack to finish charging.
  • Forgetting the handle bar must be held down while starting.
  • Charging a hot battery straight after mowing. Let it cool first.
  • Storing the battery in a freezing garage or a hot shed for long periods.
  • Replacing the battery before testing the contacts and safety key, which are free to check.

A small, soft-bristled brush makes it easy to clear grass and dust from battery contacts without bending the pins. View on Amazon

A multimeter lets you check whether a battery pack is delivering voltage before you buy a replacement. View on Amazon

A spare fully charged battery pack lets you test the mower quickly and keeps you mowing while the first pack charges. View on Amazon

FAQ

Why does my Black and Decker battery mower click but not start?

A clicking sound usually means the battery is low or not making full contact. Charge the pack fully and reseat it until it clicks firmly into place.

Can I use any charger with my Black and Decker battery?

Use the charger made for your specific battery model. Mismatched chargers can fail to charge or damage the pack. Check the label on the battery for the correct model.

When should I take the mower to a professional?

If the battery tests good and the mower still won’t start, or if you see burning smells or damaged wiring, stop using it and have a qualified technician inspect it.

Conclusion

Most Black and Decker battery mowers that won’t start can be fixed by charging the pack, reseating it, engaging the safety features and cleaning the contacts. Work through these checks in order before buying parts. If the mower still fails with a known-good battery, a qualified service technician is the safest next step.

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Graham Fisher

About Graham Fisher

Graham Fisher is part of our editorial team and reviews and edits our lawn mowers guides, checking product details against manufacturer specifications and owner feedback.