Mowers
Cordless mower troubleshooting, symptom by symptom
A battery mower has far fewer failure modes than a gas one. Most of what goes wrong is the pack, the deck or the height setting.
Affiliate disclosure: we earn a commission if you buy through our links, at no extra cost to you. It never changes which product we rank first — here is how we're funded.
We have not tested these units. Every spec on this page comes from the manufacturer's own documentation and is linked to it. Every computed figure is arithmetic you can redo. Prices are checked daily — last verified January 1, 1970. Here is exactly how we pick.
A cordless mower deleted most of the things that used to go wrong. There is no fuel to go stale, no oil to check, no spark plug to foul and no carburetor to clean. What is left is a short list, and it is worth knowing in order.
Before anything: pull the pack
Symptom: it will not start
| Check | What you are looking for | Fix |
|---|---|---|
| Pack seating | A pack pushed in but not latched | Remove and refit until it clicks |
| Pack charge | Below the tool's cutoff, which is not always zero on the gauge | Charge fully and retry |
| Safety key | Present and fully inserted | Refit; keep spares with the charger |
| Bail handle / start button sequence | Most machines need both, in order | Read the sequence on the handle decal |
| Blade free to turn | Packed clippings or a stick binding the blade | Pack out first, then clear the deck by hand with gloves |
| Terminals | Debris or moisture in the battery bay | Clear and dry before refitting |
The last mechanical item is the one people skip. If the blade cannot rotate freely, many tools will refuse to start rather than stall on the first revolution, and a deck full of dried clippings from a wet cut is enough to do it.
Symptom: it cuts out mid-lawn
This is a load problem far more often than a fault. The motor draws more current than the pack or the controller will sustain, and the tool protects itself. Three things create that load, and all three are within your control.
- Grass that is too long. Extension guidance is to remove no more than one third of the leaf tissue per cut. Breaking that rule badly is the fastest way to overload a deck.
- Grass that is wet. Wet material packs the deck and clumps. Guidance is to delay mowing when grass is wet.
- A cut height that is too low. Dropping the deck to catch up on an overgrown lawn combines both problems at once.
#ad Check the Greenworks 80V 21" 4-in-1 LM2108S price on Amazon — how we're funded.
Symptom: runtime is well short of the claim
Work through this in order, because the first three explanations are far more common than the fourth.
- The claim is a best case. Every runtime figure in this category is the manufacturer's own, measured under conditions none of them publish.
- Your conditions are harder. Thick, tall or wet growth and a low cut height all raise the draw.
- The pack is small for the job. Check the arithmetic: watt-hours divided by the tool's draw per minute. The method is in watt-hours explained.
- The pack has aged. Lithium packs lose capacity over time. Nobody in this category publishes capacity retention beyond the warranty term, which is why we cannot tell you how much — see how long mower batteries last.
#ad Check the EGO Power+ 21" Select Cut LM2135SP price on Amazon — how we're funded.
Symptom: the cut is uneven or the lawn looks ragged
| What you see | Most likely cause | What to do |
|---|---|---|
| Gray or frayed tips a day or two after mowing | A dull blade. Extension guidance: dull blades leave jagged edges and plants are more susceptible to diseases | Inspect the leading edge; sharpen or replace |
| One side cut lower than the other | Cut-height levers not matched, or a bent deck | Set every wheel to the same number and check on flat ground |
| Streaks of uncut grass between passes | Overlap too small, or blade speed dropping under load | Overlap about 10% and slow the walking pace |
| Clumps left in rows | Wet or overgrown clippings matting rather than filtering down | Bag or rake; extension guidance warns matted clippings smother grass |
| Scalped patches on humps | Deck too low for an uneven lawn | Raise the deck; extension guidance is 3 in or higher anyway |
Blade and clipping guidance from UMN Extension mowing practices and what to do with lawn clippings.
#ad Check the Greenworks 40V 20" Push LM2054 price on Amazon — how we're funded.
Things that look like faults and are not
- The mower stops when you release the handle. That is the blade brake working. Extension safety guidance names it as a safety feature and warns against tampering with it.
- The pack is warm after a hard cut. Expected. Let it cool before charging if the charger asks you to.
- Runtime is lower on the first cut of spring. That is the heaviest growth of the year meeting a best-case runtime claim.
- The self-propel feels slower uphill. Drive speeds are published as ranges — EGO publishes 0.9 to 3.1 MPH — and load sits inside that.
What we cannot tell you
We cannot diagnose your specific machine and we do not publish repair procedures. No manufacturer we cite publishes fault codes, thermal cutoff thresholds or capacity retention curves, so anything specific in those areas would be invented. The manual that came with the tool is the authority, and warranty work belongs with the manufacturer.
What this page gives you is the order to check things in, and the single instruction that comes before all of them: pull the pack first.
The products discussed
Specs are the manufacturer's own and linked to the page they came from. Prices come from a live daily check; where we have no verified price we say so rather than print a stale one.
EGO Power+ 21" Select Cut LM2135SP
EGO · EGO 56V ARC Lithium · Our score 9.1/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
The most watt-hours in the box of any flagship walk-behind here, on the platform with the widest tool range to grow into.
Published specs
| Deck | 21 in |
|---|---|
| Cutting torque | Up to 7.0 ft-lbs |
| Battery included | 56V 7.5Ah |
| Cut height | 1-4 in, 8 positions |
| Self-propel speed | 0.9-3.1 MPH |
| Runtime claim | Up to 60 min |
| Warranty | 5-yr tool / 3-yr battery |
Source: EGO POWER+ 21" Select Cut System (LM2135SP), egopowerplus.com
56V x 7.5Ah = 420Wh, using EGO's advertised pack voltage.
What the numbers favor
- 420Wh in the box -- the largest included pack of any flagship walk-behind on this page
- Eight cut-height positions from 1 to 4 in, the widest published range here
- Three interchangeable lower blades (mulching, high-lift bagging, extended runtime)
- 5-year tool warranty, the longest published on this page
What they don't
- EGO publishes torque (7.0 ft-lbs), not motor wattage, so it cannot be compared directly against Greenworks' 1500W figure
- The 7.5Ah pack that earns the runtime claim is also the expensive one to replace
your yard is under a quarter acre. You would be paying for 420Wh of headroom you will never discharge, and a 20 in push mower cuts the same grass.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
Greenworks 80V 21" 4-in-1 LM2108S
Greenworks · Greenworks 80V · Our score 8.4/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
The only mower here that publishes motor wattage, blade RPM, weight and an acreage rating -- and the only one whose battery warranty matches its tool warranty.
Published specs
| Model / SKU | LM2108S / 2550402 |
|---|---|
| Deck | 21 in |
| Max blade speed | 3200 RPM |
| Battery included | 80V 4.0Ah |
| Cut height | 1.38-4.0 in, 7 positions |
| Runtime claim | Up to 33 min |
| Weight | 75 lb |
| Rated for | Up to 1/2 acre |
| Warranty | 4-yr tool / 4-yr battery |
Source: 80V 21" 4-in-1 Self-Propelled Lawn Mower (LM2108S), greenworkstools.com
80V x 4.0Ah = 320Wh, using Greenworks' advertised pack voltage.
What the numbers favor
- 4-year battery warranty -- a year longer than EGO's 3-year, on the component that fails first
- Publishes blade RPM, weight and acreage rating; the other two brands publish none of the three
- 40-minute recharge on the included charger, the fastest published here
- 4-in-1 deck adds turbo leaf pickup on top of mulch, bag and side discharge
What they don't
- 320Wh included, the least of the three flagships -- and the 33-minute runtime claim reflects that
- 75 lb is the only published weight here, and it is not light
you want one battery to finish a half-acre without a swap. Greenworks rates the mower for 1/2 acre but claims only 33 minutes on the included pack; those two numbers only reconcile if you buy a second battery.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
Greenworks 40V 20" Push LM2054
Greenworks · Greenworks 40V · Our score 8.0/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
40 minutes on a 160Wh pack and 57.5 lb to push -- the honest answer for a third of an acre and nothing more.
Published specs
| Model / SKU | LM2054 / 2549902 |
|---|---|
| Deck | 20 in |
| Max blade speed | 3200 RPM |
| Battery included | 40V 4.0Ah |
| Cut height | 1.2-3.6 in, 7 positions |
| Runtime claim | Up to 40 min |
| Weight | 57.5 lb |
| Rated for | Up to 1/3 acre |
| Warranty | 3-yr tool / 3-yr battery |
Source: 40V 20" 4-in-1 Push Lawn Mower (LM2054), greenworkstools.com
40V x 4.0Ah = 160Wh. Note it claims 40 minutes on 160Wh where the 80V flagship claims 33 minutes on 320Wh -- a 20 in deck and no self-propel drive motor is why.
What the numbers favor
- Lightest published weight on this page at 57.5 lb, and the only sub-60 lb mower here
- Claims 40 minutes from 160Wh -- the best published minutes-per-watt-hour of any mower on this page
- Same 3200 RPM blade speed as the 80V flagship
- 4-in-1 deck at the entry price
What they don't
- Push only -- no drive assist on any slope
- 1.2 in minimum cut height is lower than most cool-season lawns should ever be cut
- 120-minute recharge, three times the 80V model's 40 minutes
your lawn is over a third of an acre or has any real slope. Greenworks rates it to 1/3 acre and you will be pushing all 57.5 lb of it up the hill yourself.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
Where to buy the tools on this page
Every link below is an Amazon affiliate link. We show no price we have not verified today, so where there is no live figure the link says "check price" and takes you to the listing to read it there.
Best overall
EGO Power+ 21" Select Cut LM2135SP
EGO · EGO 56V ARC Lithium
Best published spec sheet
Greenworks 80V 21" 4-in-1 LM2108S
Greenworks · Greenworks 80V
Best for small yards
Greenworks 40V 20" Push LM2054
Greenworks · Greenworks 40V
#ad As an Amazon Associate we earn from qualifying purchases, at no extra cost to you. How we're funded.
Common questions
Why won't my battery lawn mower start?
Why does my cordless mower cut out mid-lawn?
Why is my mower's runtime shorter than advertised?
Why is my lawn cut unevenly?
What is the first thing to do before troubleshooting?
My mower keeps clogging. What is wrong?
Sources
- Mowers and mowing safety, University of Minnesota Extension
- Mowing practices for healthy lawns, University of Minnesota Extension
- What to do with lawn clippings, University of Minnesota Extension
- EGO POWER+ 21" Select Cut System (LM2135SP), egopowerplus.com
- Greenworks 80V 21" 4-in-1 Self-Propelled Lawn Mower (LM2108S), greenworkstools.com
- Greenworks 40V 20" 4-in-1 Push Lawn Mower (LM2054), greenworkstools.com
Read next
- Mowers
Deck width sets how fast you finish. Watt-hours set whether you finish at all.
- Battery lawn mower maintenance: what is actually left to do
Five maintenance jobs removed, one added. The short list that remains, and the storage habits that matter.
- Mower blades: mulching, high-lift, and when to change them
Mulching against high-lift, what a dull blade costs the lawn, and the multi-blade systems.
- How long do electric lawn mower batteries last?
Runtime per charge is arithmetic. Lifespan in years is mostly warranty terms and honest uncertainty.
- Should you mow wet grass?
Delay if you can: footing, clumping and disease spread are the published reasons.
- Yard tool safety, from the published guidance
CDC, CPSC and extension guidance for saws, washers and mowers, in one place.