Greenworks 21 in. 40V Brushless Cordless Battery Walk-Behind Push Lawn Mower, 5.0 Ah USB Battery & Charger

Thank you for your feedback. We are glad to hear you are otherwise satisfied with the lawnmower, and we’re sorry that the runtime has not met your expectations. Under typical conditions, a 40V 5.0Ah battery can provide up to 45 -60 minutes of runtime. That said, a mower with this battery size is better suited for smaller yards or lighter mowing conditions, and it may not be able to complete a full 1/3 acre on a single charge depending on grass height, thickness, moisture, terrain, and mowing pace. Cutting dense or overgrown grass, using a lower deck height, or mowing under heavier load can reduce runtime and may require multiple charge cycles to finish larger areas. For best results, we recommend mowing regularly to avoid cutting more than one-third of the grass height at a time, using a higher deck setting when possible, and ensuring the battery is fully charged before use. Greenworks 40V tools and batteries are backed by a three-year limited warranty when purchased from an authorized retailer, and our success team would be happy to review your case and help determine the next best steps. They can be reached either using the online chat function, on Greenworks Tools page, or by calling 1-888-909-6757.

We are sorry to hear about your experience and understand how frustrating it can be when the mower is not meeting expectations for your yard. Performance and runtime can vary quite a bit depending on grass conditions, and thicker or taller grass will place a heavier load on the motor and battery. For best results, we recommend mowing when grass is dry, keeping the cutting height higher for the first pass if the lawn is overgrown, and avoiding removing more than one-third of the blade length at a time, this can help prevent bogging down and improve overall efficiency. You may also see improved performance by using a fully charged higher-capacity battery and ensuring the blade is sharp, as a dull blade can reduce cutting performance and increase power draw. For a 1/4 acre yard, especially with denser grass, a higher voltage platform (such as 60V or 80V) or a self-propelled model may be better suited for handling tougher conditions more consistently. If you would like, our support team can help review your setup and provide tailored recommendations to improve performance. They can be reached either using the online chat function, on Greenworks Tools page, or by calling 1-888-909-6757.

Hello Junk. Thank you for your feedback. We are sorry to hear about the issues you are experiencing with your 21″ 40V Lawn Mower. What you are describing as the lawn mower running for a few seconds and then shutting off is not typical performance and usually indicates one of the following:
Battery/connection issue: Ensure the battery is fully charged and seated firmly in the mower. Check that the contacts on both the battery and mower are clean and free of debris.
Safety/engagement switch: The lawn mowers require the bail lever to be held properly, and all safety interlocks engaged. If a sensor is not detecting the lever or deck cover properly, it can shut the motor off.
Motor load cutoff: If the blade is blocked or the mower is under heavy load right at start, the motor may shut off quickly to protect the system. Make sure the deck is clear and the blade spins freely by hand (with the battery removed).
Fault code or component fault: Some units will shut down immediately if a component (controller, motor, sensor) is malfunctioning.
Before assuming a defective unit, try these troubleshooting steps:
Fully charge the battery and reseat it.
Verifying all safety levers are properly engaged.
Remove the battery and check for debris in the contacts.
With the battery out, confirm that the blade can spin freely and that there are no obstructions under the deck.
If the mower still shuts off after these checks, it may require service or a replacement part especially if it happens with a good battery and no load. Please reach out to our Customer Success team with your serial number and purchase details so we can assist you further. We want to ensure you get reliable performance from your lawn mower.
They can be reached either using the online chat function, on Greenworks Tools page, accessible by clicking “Chat Now” in the bottom corner of your screen, Chat with a Live Agent or by calling 1-888-909-6757.