By Graham FisherUpdated November 2026
If your greenworks 40v lawn mower won’t start, the problem is often the battery, the safety key or a loose connection rather than the motor itself. Before you buy anything, it helps to know what separates one battery mower from another. This guide compares three Greenworks 40V push mowers on the criteria that matter most when you are choosing a replacement or a first cordless mower: battery capacity, cutting width for your yard, motor design, and the kinds of owner feedback that tend to come up again and again. We looked at published specifications, the brand’s reputation for battery systems, and common owner feedback patterns. We did not run these machines ourselves.
Our top picks at a glance
- 1
TOP CHOICEBest overallGreenworks 40V 20in Push Lawn Mower, 4.0 Ah Battery and ChargerView on Amazon - 2
Best for larger lawnsGreenworks 40V 21in Push Lawn Mower, 5.0 Ah Battery and ChargerView on Amazon - 3
Best for two-battery rotationGreenworks 48V (24V x 2) 20in Push Lawn Mower, (2) 4.0 Ah Batteries KitView on Amazon
Our Top Picks
Quick Comparison
| Product | Best for | Key feature |
|---|---|---|
| Greenworks 40V 20in Push Lawn Mower, 4.0 Ah Battery and Charger | Small to mid-size yards that want a straightforward single-battery setup | Brushless motor with push-button start |
| Greenworks 40V 21in Push Lawn Mower, 5.0 Ah Battery and Charger | Mid-size lawns where a wider deck and larger battery reduce stops | 21-inch cutting width with 5.0 Ah battery |
| Greenworks 48V (24V x 2) 20in Push Lawn Mower, (2) 4.0 Ah Batteries Kit | Owners who want to charge one battery while mowing with the other | Two 4.0 Ah batteries and dual-port charger |
Greenworks 40V 20in Push Lawn Mower, 4.0 Ah Battery and Charger
GreenworksBrushless motor with aluminum handles and LED headlight; push-button start and quiet operation simplify lawn care. 40V 20in Push Lawn Mower, 4.0 Ah Battery and Charger
Best for: Small to mid-size yards that want a straightforward single-battery setup.
This is the most natural starting point for someone whose greenworks 40v lawn mower won’t start and who is considering a like-for-like replacement. It uses one 40V battery, a brushless motor and push-button starting, so there is no cord, no gas and no pull cord to fight with.
Key specs
- 40V battery platform
- 20-inch cutting width
- 4.0 Ah battery with charger included
- Brushless motor
- Push-button start, aluminum handles, LED headlight
Pros
- Push-button start removes the pull-cord hassle
- Brushless motor is generally quieter and more efficient than brushed designs
- Single battery keeps the setup simple to store and charge
Cons
- A 4.0 Ah battery may need a recharge partway through a large lawn
- The 20-inch deck means more passes on bigger properties
Bottom line: A good pick for owners with a modest lot who want a simple, familiar Greenworks setup.
Greenworks 40V 21in Push Lawn Mower, 5.0 Ah Battery and Charger
GreenworksBrushless push mower with quiet operation; gas-free design eliminates fumes and pull starts for hassle-free mowing. 40V 21in Push Lawn Mower, 5.0 Ah Battery and Charger
Best for: Mid-size lawns where a wider deck and larger battery reduce stops.
If your yard is a bit larger than what a 20-inch deck handles comfortably, this model adds width and a bigger battery. It is a natural step up when you are replacing an older mower and want more coverage per charge.
Key specs
- 40V battery platform
- 21-inch cutting width
- 5.0 Ah battery with charger included
- Brushless, gas-free design
Pros
- Wider deck covers ground faster than a 20-inch model
- Larger battery gives more runtime per charge
- No fuel, oil or pull starting to maintain
Cons
- Heavier than the 20-inch version, which matters on hills or for shorter users
- Higher battery capacity means longer charging time between sessions
Bottom line: Best for owners with a medium lawn who want more cutting width and runtime from a single battery.
Greenworks 48V (24V x 2) 20in Push Lawn Mower, (2) 4.0 Ah Batteries Kit
GreenworksBrushless motor with LED headlight and dual port rapid charger, push-button start for easy lawn care. 48V (24V x 2) 20in Push Lawn Mower, (2) 4.0 Ah Batteries Kit
Best for: Owners who want to charge one battery while mowing with the other.
This model uses two 24V batteries to deliver 48V total. Its appeal is continuity: when one pack runs low, you swap in the other and keep going. It suits people who mow on a regular schedule and do not want to wait for a recharge.
Key specs
- 48V system (two 24V batteries)
- 20-inch cutting width
- Two 4.0 Ah batteries included
- Dual-port rapid charger
- Brushless motor with LED headlight
Pros
- Two batteries allow continuous mowing with a quick swap
- Dual-port charger can top off both packs at once
- Push-button start and brushless motor carry over from the single-battery line
Cons
- Two batteries and a dual-port charger take more room to store
- Carrying a second pack adds weight and cost of ownership
Bottom line: The right choice if you mow often and want to avoid downtime, or if you already own Greenworks 24V batteries.
Buying Guide
Battery Platform and Compatibility
Check which battery system your mower uses before you buy. A 40V and a 24V pack are not interchangeable, and mixing chargers and packs across platforms can damage cells or prevent charging. Look at the label on the battery and the mower’s model plate. If your current mower won’t start, first confirm the battery is fully charged and seated, because many “dead mower” calls are simply a pack that didn’t click into place.
Good picks for this: Greenworks 40V 20in Push Lawn Mower, 4.0 Ah Battery and Charger; Greenworks 48V (24V x 2) 20in Push Lawn Mower
Battery Capacity (Ah Rating)
Amp-hour (Ah) rating roughly indicates how long a battery can run between charges. A 4.0 Ah pack suits smaller lots, while a 5.0 Ah pack gives more runtime on mid-size yards. Higher capacity usually means longer charging time, so consider how quickly you need the mower back in service.
Good picks for this: Greenworks 40V 21in Push Lawn Mower, 5.0 Ah Battery and Charger; Greenworks 40V 20in Push Lawn Mower, 4.0 Ah Battery and Charger
Cutting Width and Lawn Size
A 20-inch deck needs more passes than a 21-inch deck on the same lawn, and the difference adds up on lots over a quarter acre. Measure your mowing area and count how many passes it would take. Narrower decks are easier to maneuver around beds and trees.
Good picks for this: Greenworks 40V 21in Push Lawn Mower, 5.0 Ah Battery and Charger; Greenworks 40V 20in Push Lawn Mower, 4.0 Ah Battery and Charger
Starting System
Push-button start eliminates the pull cord, which is helpful for users with limited upper-body strength. Confirm the start button, safety key or bail bar is in working order if the mower won’t start, since these interlocks are a common reason for no-start complaints. The Greenworks models here use push-button starting.
Good picks for this: Greenworks 40V 20in Push Lawn Mower, 4.0 Ah Battery and Charger; Greenworks 40V 21in Push Lawn Mower, 5.0 Ah Battery and Charger
Charging Setup
Think about how you will charge. A single-port charger handles one pack at a time, while a dual-port charger can top off two batteries simultaneously. If you own two packs, a dual-port setup saves time. Keep chargers in a dry, temperate spot, since extreme heat or cold can reduce battery life.
Good picks for this: Greenworks 48V (24V x 2) 20in Push Lawn Mower, (2) 4.0 Ah Batteries Kit
Weight and Handling
Electric push mowers are heavier than many gas models because the battery adds mass. Test how the handle height feels and whether the mower is easy to push up slopes. Aluminum handles, as found on the Greenworks 20-inch model, reduce weight compared with steel.
Good picks for this: Greenworks 40V 20in Push Lawn Mower, 4.0 Ah Battery and Charger; Greenworks 48V (24V x 2) 20in Push Lawn Mower
Maintenance and Care
Keep the blade sharp, clear grass from the deck after each use, and store batteries at moderate temperatures. Brushless motors generally need less maintenance than brushed motors, but the deck, wheels and battery contacts still benefit from periodic cleaning.
Good picks for this: Greenworks 40V 21in Push Lawn Mower, 5.0 Ah Battery and Charger; Greenworks 40V 20in Push Lawn Mower, 4.0 Ah Battery and Charger
FAQ
Why won’t my greenworks 40v lawn mower start even with a full battery?
A charged battery doesn’t guarantee power reaches the motor. Check that the battery is fully seated, the safety key or bail bar is engaged, and the battery contacts are clean. A loose connection or a blown fuse in the mower can also block starting. Our separate troubleshooting guides walk through these checks in order.
How do I know if the battery or the mower is at fault?
Try the battery in another compatible Greenworks tool or charge it fully and test again. If the battery powers other equipment and the mower still won’t start, the problem is more likely in the mower. Battery packs can also lose capacity over several years, so a pack that won’t hold a charge may need replacing.
Can I use a 40V battery in a 24V mower?
No. Battery platforms are voltage-specific, and you should only use batteries and chargers designed for your mower. Mixing platforms can damage equipment or create a safety hazard.
Does a higher Ah battery make the mower start more reliably?
Not directly. Ah rating affects runtime, not starting. A higher-capacity battery will run longer per charge, but starting problems usually come from connections, interlocks or the battery’s state of charge.
How long should a Greenworks battery last?
Lifespan depends on charge cycles, storage temperature and care. Manufacturers typically describe battery life in terms of charge cycles rather than years. Storing batteries indoors at moderate temperatures and avoiding deep discharges generally extends service life.
Is a brushless motor worth it on a battery mower?
Brushless motors are generally more efficient, run cooler and need less maintenance than brushed motors. Owners often report they feel quieter and last longer, which is why most current Greenworks 40V push mowers use this design.
Conclusion
If your greenworks 40v lawn mower won’t start, the fix may be as simple as checking the battery seating and safety interlocks. When you are ready to replace or upgrade, the right model depends on your lawn. The Greenworks 40V 20in with a 4.0 Ah battery suits smaller yards and a simple setup. The 40V 21in with a 5.0 Ah battery fits mid-size lawns that need more width and runtime. The 48V two-battery kit makes sense for owners who mow often and want to avoid waiting for a recharge.
Sources
- Guidance on lithium-ion battery handling, storage and recycling (energy.gov)
- Safety recalls and consumer product safety guidance for lawn equipment (cpsc.gov)
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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.
