Guide · Garden · 4 models
Cordless mower batteries explained: volts, amp-hours, watt-hours and how much lawn you actually get
Cordless mowers are labelled 18, 20, 40 or 48 V, sold with a 2.0 or 4.0 Ah battery and a lawn size, as if any one number told you the run time. None does alone. This guide turns volts and amp-hours into watt-hours you can compare, and explains brushless motors, the makers' lawn assumptions and battery platforms, with four mowers as examples.
Three numbers that are really one
A battery label says 18 V 4.0 Ah. The volts are the electrical pressure the motor runs at; the amp-hours are how much charge the pack holds. Neither alone is a run time. Multiply them and you get watt-hours, the energy in the pack, which is the number that lets you compare one mower’s battery with another’s:
| Mower | Battery | Watt-hours (computed) |
|---|---|---|
| Einhell GE-CM 18/33 Li | 18 V × 4.0 Ah | 72 Wh |
| Worx WG733E | 20 V × 4.0 Ah | 80 Wh |
| Worx WG779E.2 | 2 × (20 V × 2.0 Ah) | 80 Wh |
| Gtech CLM50 | 48 V × 2.0 Ah | 96 Wh |
The watt-hours are our arithmetic on the makers’ figures. Note that the two Worx mowers carry the same energy: one in a single 4.0 Ah pack, the other in two 2.0 Ah packs wired in series to make 40 V. The 40 V mower can draw more power at once, which is why it has a wider deck and a roller, but it does not have more lawn in the battery.
one 20 V 4.0 Ah battery, brushless, 200 m² by the maker
Worx WG733E 20V Brushless (33 cm)
- Cutting width
- 33 cm
- Cutting height
- 25–75 mm, 6 steps
- Grass bag
- 35 l
- Motor
- Brushless, IntelliCut
- Battery
- 20 V, 1 × 4.0 Ah, charger included
- Lawn per charge
- 200 m²†
Check price on Amazon
One 20 V 4.0 Ah PowerShare battery, 80 Wh, driving a brushless 33 cm mower that Worx rates for 200 m² on its UK page (and 250 and 300 elsewhere, which is why that fact is flagged).
Strengths
- 10 kg with battery, the lightest full mower here
- Six heights up to 75 mm for a long first cut
- Three-year warranty on registration
Limitations
- Worx's own pages quote 200, 250 and 300 m² for the same mower
- One 4.0 Ah battery; a second is extra
Good for
- a small lawn and a shed with Worx 20 V tools
- anyone who finds mowers heavy to lift
Look elsewhere if
- a lawn over 200 m² on one battery
two 20 V 2.0 Ah batteries in series, brushed, 230 m²
Worx WG779E.2 40V (34 cm, 2 batteries)
- Cutting width
- 34 cm
- Cutting height
- 20–70 mm, 6 steps
- Grass bag
- 30 l
- Motor
- Brushed
- Battery
- 2 × 20 V 2.0 Ah (40 V), dual charger included
- Lawn per charge
- 230 m²
Check price on Amazon
Two 20 V 2.0 Ah batteries, also 80 Wh, in series for 40 V, driving a brushed 34 cm mower with a roller that Worx rates for 230 m².
Strengths
- Two batteries in the box and a dual charger
- 20 mm minimum for a short formal cut, roller for stripes
- Three-year warranty on registration
Limitations
- Brushed motor
- 30 l bag on a 34 cm deck fills quickly
- Weight figures differ by nearly a kilo
Good for
- a 150 to 230 m² lawn you want striped
Look elsewhere if
- someone who already owns one PowerShare battery and wants to use it; this needs two
Where the energy goes
A mower’s motor spends its watt-hours on three things: spinning the blade through air, cutting grass, and in a brushed motor, heat in the brushes. Brushless motors skip the third and control their speed electronically, so they take only the power the grass needs. That is why the three brushless mowers in our shortlist (Worx WG733E, Bosch Rotak 18V-32, Einhell) state 150 to 200 m² from 72 to 80 Wh, and why a brushed mower of the same energy does less in thick grass even if its headline figure is similar.
one 18 V 4.0 Ah battery, brushless, 200 m² recommended
Einhell GE-CM 18/33 Li (4.0 Ah kit)
- Cutting width
- 33 cm
- Cutting height
- 25–65 mm, 5 steps
- Grass box
- 30 l
- Motor
- Brushless (PurePOWER)
- Battery
- 18 V Power X-Change, 1 × 4.0 Ah, fast charger included
- Lawn per charge
- 200 m²
Check price on Amazon
An 18 V 4.0 Ah Power X-Change pack, 72 Wh, and a brushless PurePOWER motor; Einhell recommends it for 200 m², a plain statement that most makers avoid.
The blade matters too. A 42 cm blade moves more air and cuts more grass per second than a 32 cm one, which is why the Gtech CLM50 carries 96 Wh and states its figure as time rather than area.
Strengths
- Battery platform with the widest range of tools in this group
- Brushless motor and a fill indicator at a low price
- Einhell states the lawn size plainly: 200 m²
Limitations
- Smallest box here at 30 l
- Weight figures differ by 300 g between Einhell and the listing
Good for
- a 150 to 200 m² lawn and a Power X-Change drill in the garage
Look elsewhere if
- long or wet grass, where a 30 l box fills fast
one 48 V 2.0 Ah battery, stated as 40 minutes
Gtech CLM50 Cordless Lawnmower
- Cutting width
- 42 cm
- Cutting height
- 30–80 mm, 10 steps
- Grass box
- 50 l
- Battery
- 48 V 2.0 Ah, charger included
- Run time
- Up to 40 min
- Charge time
- 1 h
Check price on Amazon
A 48 V 2.0 Ah pack, 96 Wh, behind a 42 cm blade: Gtech says up to 40 minutes, with a one-hour charge, rather than a lawn size. Forty minutes at a 42 cm width covers more lawn than the 18 V mowers’ 200 m² in practice, but Gtech leaves the arithmetic to you.
Strengths
- 42 cm cut and a 50 l bin halve the passes and the emptying
- Run time and charge time stated by the maker
- Heights to 80 mm for an overgrown lawn
Limitations
- 13.5 kg, the heaviest here
- Proprietary battery; no other tools share it
Good for
- a medium lawn up to about 300 m² mown in one go
Look elsewhere if
- a tiny lawn or a narrow side gate
What the lawn figure assumes
Every maker’s square-metre claim is for dry grass, cut regularly, at a middle height, with a fresh battery. The same mower on the first cut of April, in long wet grass, does half or less. Worx’s manual for the WG779E illustrates the range: 230 m² with the 2.0 Ah packs, 280 with 2.5 Ah and 460 with 4.0 Ah, on thin dry grass. The figure to plan on is two thirds of the box.
Charging and the second battery
A 4.0 Ah battery on a standard 18 or 20 V charger takes one and a half to two hours by the retailers’ figures; Gtech states one hour for its 48 V pack; Einhell ships a fast charger. If the lawn is bigger than the box figure, a second battery is the answer: it costs a fraction of the mower, it charges while you mow, and on the shared platforms it runs the hedge trimmer afterwards.
The platforms
The battery that comes with a mower fits other tools from the same system, and the systems are the real brand decision:
- Power for All (18 V): Bosch home tools, Flymo, Gardena and others. The Bosch Rotak 18V-32 and Flymo SimpliMow 320 share it.
- Worx PowerShare (20 V): every Worx 20 V tool, and 40 V tools take two packs. Both Worx mowers.
- Einhell Power X-Change (18 V): hundreds of Einhell tools from drills to chainsaws. The Einhell GE-CM 18/33 Li.
- Gtech: Gtech’s own packs; the CLM50’s 48 V battery fits only Gtech.
If you already own one of the first three systems, buy that mower as a bare unit and a second battery, and skip the kit.
How to read a mower listing’s battery line
- Volts and amp-hours. Multiply them: that is the energy.
- How many packs are in the box, and whether the mower needs two at once.
- Brushless or not. Brushless gets more lawn from the same energy.
- The lawn figure, and whether the maker states it (Einhell, Worx, Flymo) or a retailer does (Bosch).
- The platform, because the second battery and the next tool depend on it.
Which battery, by lawn
- Under 100 m²: any 18 or 20 V 4.0 Ah kit; the Flymo if price matters, the Worx WG733E if weight does.
- 100 to 200 m²: a brushless 18 or 20 V 4.0 Ah mower: Worx WG733E, Bosch, Einhell.
- 200 to 300 m²: the Gtech CLM50’s 96 Wh and 42 cm blade, or any of the above with a second battery.
- Striped and short: the Worx WG779E.2, with its two packs.
Sources
Facts checked 23 October 2026
- Worx UK — WG733E product page — Manufacturer documentation, checked 23 October 2026
- Amazon listing (WORX) — Retailer listing, checked 23 October 2026
- Worx UK — WG779E.2 product page — Manufacturer documentation, checked 23 October 2026
- Amazon listing (WORX) — Retailer listing, checked 23 October 2026
- Einhell UK — GE-CM 18/33 Li (1 × 4.0 Ah) product page — Manufacturer documentation, checked 23 October 2026
- Amazon listing (Einhell) — Retailer listing, checked 23 October 2026
- Gtech — CLM50 cordless lawnmower product page and user manual — Manufacturer documentation, checked 23 October 2026
- Amazon listing (Gtech) — Retailer listing, checked 23 October 2026
Is 40 V twice as good as 20 V?
No. Voltage is pressure, amp-hours are the tank; energy is the product of the two. The Worx WG779E.2's two 20 V 2.0 Ah batteries in series hold the same energy as one 20 V 4.0 Ah battery in the WG733E: 80 watt-hours either way. The 40 V motor can draw more power at once, which helps in long grass; it does not run longer.
What is a watt-hour and why do makers not print it?
Volts times amp-hours: an 18 V 4.0 Ah battery is 72 Wh, a 48 V 2.0 Ah battery is 96 Wh. It is the one number that compares batteries across brands, which is probably why the boxes lead with volts instead. We compute it below; it is arithmetic on the makers' figures, not a maker's claim.
How long does a charge take?
Depends on the charger in the kit, which makers rarely state clearly. Gtech says one hour for the CLM50's 48 V battery; Einhell supplies a fast charger; Bosch's AL 18V-44 is its standard 18 V charger; retailers quote 1.5 to 2 hours for the Flymo kit. A second battery is cheaper than a faster charger and doubles the lawn.
Will the battery last?
Lithium packs lose capacity with full discharges and heat. Stop mowing when the mower slows rather than running it flat, store the battery indoors over winter at about half charge, and expect five or more seasons. Every brand here sells the battery separately, so a dead cell is not a dead mower.
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