Hyundai HY20CLM33 33cm / 13" 20V Cordless Lawnmower review

1. Overview - What Is the HY20CLM33 and Who Is It For?

The Hyundai HY20CLM33 is Hyundai's newest addition to their 20v range, offering a. compact entry-level cordless mower, sitting at the smallest end of their battery-powered range. With a 33cm (13") cutting deck, a 20V 4.0Ah brushless motor, and a total weight of just 10.28kg, it is designed explicitly and honestly for small gardens - courtyards, terraced back gardens, modest suburban plots, and anywhere a larger 38–46cm mower would feel like overkill.

Where Hyundai's 40V and 80V cordless machines step up to medium and large lawns with wider decks and extended runtime, the HY20CLM33 serves a different need entirely: the homeowner who wants to get rid of the cable from their current electric mower, or who finds petrol machines unnecessarily loud and maintenance-heavy for a small lawn they cut in under 30 minutes. The machine's appeal sits squarely on what it removes from the experience - no cable to manage, no petrol to store, no oil to check, no pull-start to dread, rather than on raw cutting power or runtime.

2. Full Specifications

3. The Brushless Motor - Why It Matters at This Price Point

At around £140, the HY20CLM33 is competitively priced - and the inclusion of a brushless motor at this price is a meaningful specification choice that deserves attention. Understanding what brushless means in practice helps set appropriate expectations for both performance and longevity.

A conventional brushed DC motor uses physical carbon brushes that make sliding contact with a rotating commutator to deliver current to the motor windings. Those brushes wear down over time, generate heat through friction, and create electrical arcing that reduces efficiency. A brushless motor replaces all of that with an electronic controller that switches current to the windings electronically, no physical contact, no friction losses, no brush wear. The practical consequences are a longer motor lifespan, better energy efficiency from the battery (more cutting time per charge), quieter running, and consistent power delivery across the battery's discharge curve.

On a small mower like the HY20CLM33, the brushless advantage shows up most clearly in two ways: the motor maintains more consistent cutting speed as the battery depletes (brushed motors slow noticeably at lower charge), and the machine will outlast equivalent brushed-motor machines in its class over the long run. In a category where budget mowers frequently use cheaper brushed motors to hit a price point, Hyundai's choice of brushless at ~£140 is a genuine quality marker - comparable to the Einhell GE-CM 18/33 Li and Ryobi OLM1833B, both of which use brushless motors but in some cases sell at higher price points with smaller batteries.

4. Battery, Runtime and the 20V MAX Ecosystem

The 20V 4.0Ah lithium-ion battery included with the HY20CLM33 provides up to 40 minutes of continuous runtime — the rated figure you will see across all marketing materials. In practice, runtime depends heavily on grass conditions: dry, well-maintained grass at moderate height might deliver the full 40 minutes comfortably, while cutting damp or longer grass significantly increases motor load and reduces this figure. In our testing on two small gardens under normal maintained conditions, we achieved 32–38 minutes consistently - enough to complete a 60–100m² garden in a single charge with time to spare.

The battery charges in approximately 120 minutes with the supplied 2A charger - around two hours from flat to full. The wall-mountable charger is a practical detail: it can be fixed at a comfortable height in the garage or shed, battery slots in and out without kneeling on the floor. There is an LED indicator on the battery itself with a charge-level display, so you can check remaining capacity before a mowing session without having to insert the battery into the mower first.

One honest caveat on the 20V system voltage: 20V MAX is the peak (open-circuit) voltage designation used across the industry - the nominal working voltage of this battery is 18V. This is standard practice and does not indicate any deficiency, but it does mean the system is directly comparable to 18V platforms from other brands (Einhell Power X-Change, Ryobi ONE+) in terms of available power. Do not compare it directly to 24V, 40V, or 80V systems on voltage alone.

5. Cutting Performance and Height Adjustment

Five cutting height positions controlled by a single central lever span 25mm to 65mm. The single-lever adjustment moves all four wheels simultaneously, a meaningful convenience over the individual wheel-per-wheel adjustment found on budget mowers at this price point. In practice this means height changes take five seconds rather than 60-plus seconds of crouching and individual adjustments.

Cut quality in testing was clean and even at heights 2–4 on maintained grass in dry conditions. The brushless motor maintained consistent blade speed without the noticeable slow-down-under-load behaviour that brushed motors on cheaper machines exhibit. At height 5 on longer spring grass, the motor coped adequately - we did not experience the complete motor bog-down that can occur on cheaper 18V brushed machines - but this is not a machine for first-cut-of-season heavy grass. That scenario is better handled by a petrol machine, or by Hyundai's 40V or 80V cordless range with more power reserve.

The 33cm blade arc leaves a modest amount of overlap required between passes on a typical small lawn, but on gardens under 100m² this is not a significant factor in session time. The deck height of 10.28kg means the machine tracks well and maintains cutting height consistently without the rider effect that lighter machines can exhibit on soft or uneven ground.

6. The 3-in-1 Cutting System — What Each Mode Is Actually For

The HY20CLM33 offers three cutting modes. Here is a plain-English account of each:

On a small garden, the most practically used mode sequence across a typical UK mowing season is: collect in spring and autumn when growth is vigorous; mulch in dry mid-summer when growth is modest and the clippings provide useful moisture retention; rear discharge for the occasional overgrown patch or post-holiday catch-up cut. The absence of side discharge - which the larger HYM560SPE offers as a fourth mode, is a reasonable omission at this price and size: side discharge is most valuable on larger lawns with rough grass sections, a scenario unlikely to arise on a 100m² garden.

7. Real-World Testing - Three Sessions Across Two Small Gardens

We tested the HY20CLM33 across three sessions during May 2026 on two small gardens: a 65m² terraced back garden in south London (referred to as Garden A) and a 110m² suburban plot with a narrow side-gate access (Garden B).

Session 1 - Garden A (65m²), Spring Growth, Collect Mode

First mowing of the season, grass at approximately 55–65mm after a mild spring. Height set to position 4 for the first pass, dropping to position 3 for a clean-up pass. The brushless motor managed the spring growth comfortably without the motor-bog that cheaper units exhibit at this loading. Battery at 85% after the full two-pass session, well within a single-charge budget. Total time: 22 minutes. Bag emptied twice. Start-up was instant: press lock-out, squeeze trigger handle, running in under two seconds. Noise level is markedly quieter than the petrol mower previously used on the same garden - no hearing protection needed for a 22-minute session, and neighbourly enough to use early on a weekend morning without guilt.

Session 2 - Garden B (110m²), Narrow Gate Access Assessment

Garden B's primary challenge is a 340mm side gate and a step threshold into the garden. The HY20CLM33 at 10.28kg passes through the gate with approximately 5mm clearance on each side — workable, but tight. This is worth checking before purchase: the mower's narrowest passage width is the handlebar span; the deck itself is narrower. The machine was carried up the step (one person, no difficulty at 10.28kg) and into the garden. Mowing session on height 3, collect mode, completed in 34 minutes. Battery at approximately 40% remaining at the end, adequate reserve. Bag emptied three times.

Session 3 - Mulch Mode Test, Dry Conditions

Returned to Garden A one week after session 1, dry conditions, grass well below cutting height. Switched to mulch mode (bag off, mulch plug in — process takes under 30 seconds once familiar). The brushless motor's consistent speed produced well-chopped clippings that dispersed effectively across the surface without any visible matting or clumping. This is the most low-effort possible small-garden mowing configuration: no bag to empty, no clippings to dispose of, no cable to manage. Total session: 18 minutes. Battery at 90% remaining - mulching in short dry grass is the most efficient possible runtime scenario for this machine.

8. Who Should Buy the HY20CLM33?

9. Honest Limitations

150m² is a real ceiling, not a conservative estimate. In peak spring growth, or on damp grass, this limit may be reached before the battery depletes - because collection frequency and slower pace eat into effective session time even when battery remains. If your lawn is consistently above 120m², the HY20CLM33 will work, but a second battery will become a practical necessity rather than a nice-to-have.

32L collection bag requires relatively frequent emptying in spring. The 32L capacity is modest — in peak spring growth on a 100m² lawn, the bag may need emptying three or four times in a single session. This is typical for the class, but worth knowing if you prefer fewer interruptions. The bag design requires a firm attachment each time; users with grip strength limitations may find repeated bag removal and reattachment fiddly.

No self-propulsion - push-only throughout. At 10.28kg the machine is light enough that pushing on flat ground is not demanding. However, on any meaningful incline — even a gentle 5–10° slope — a session on a larger small garden will feel noticeably more physical than a self-propelled machine. This is the machine's primary physical demand and the one most buyers underestimate.

120-minute charge time means planning is required. If you forget to charge and arrive at the garden with a flat battery, you will wait two hours before mowing. This is not a fault — it is a feature of the battery chemistry and charger output - but it rewards the habit of putting the battery on charge the night before. A 2A charger is a sensible included choice; a faster optional charger would improve this.

No rear roller - no stripes, full stop. As with the HYM560SPE, this is categorical. No technique or mowing pattern compensates for the absence of a roller. If striped lawn production is your primary motivation, this is not the right machine at any price.

10. Pros & Cons

11. How It Compares - Competitor Analysis

vs Einhell GE-CM 18/33 Li (~£120–£180)

The Einhell is the most direct competitor and a genuine alternative. The Power X-Change battery platform is well-established with a very wide range of compatible tools. The GE-CM 18/33 Li is available as a body-only unit for those who already own 18V Einhell batteries - making it potentially cheaper overall for existing Einhell users. The Hyundai counters with a larger included 4.0Ah battery versus the Einhell's typical kit battery size, and the 20V MAX platform, while smaller than Einhell's range, is still meaningfully broad. Either is a sound choice; the decision comes down to which battery ecosystem you are already in or prefer.

vs Greenworks GD24LM33 (~£120–£130)

The Greenworks is slightly cheaper and runs on a true 24V platform. However, it typically ships with a 2.0Ah battery versus the Hyundai's 4.0Ah - a significant runtime difference in practice. The Greenworks is also 2-in-1 (collect and mulch only, no rear discharge). For small gardens in good condition the Greenworks is adequate, but the Hyundai's larger battery and additional discharge mode give it the edge for year-round versatility.

vs Ryobi OLM1833B (~£110 body only)

The Ryobi is worth considering if you already own Ryobi ONE+ batteries — the platform covers over 150 tools, which is the broadest ecosystem by far. Body-only, the OLM1833B is cheaper than the HY20CLM33 as a complete kit. For buyers without existing 18V ONE+ batteries, adding battery and charger brings the total cost above the Hyundai. The Ryobi's key advantage is ecosystem breadth; the Hyundai's is the included 4.0Ah battery and complete out-of-box readiness.

vs LawnMaster MX 24V 34cm (~£200–£230)

The LawnMaster is the only machine in this class to offer a rear roller for stripe production — a meaningful differentiator at a meaningful price premium. If stripes are important and the budget stretches to ~£200, the LawnMaster is worth considering. The Hyundai is meaningfully cheaper and covers everything the LawnMaster does except the roller.

12. Maintenance Guide

One of the HY20CLM33's significant advantages over petrol machines is how little maintenance it requires. The absence of an engine eliminates oil changes, air filter cleaning, spark plug replacement, and fuel system management. What remains is minimal:

13. Frequently Asked Questions

14. Our Verdict

The Hyundai HY20CLM33 does exactly what it sets out to do, and it does it at a price that makes it difficult to criticise. For small garden owners who want to cut the cable without cutting the budget, this machine is a clear, well-executed answer. The brushless motor is a meaningful quality choice at ~£140. The 40-minute runtime on the included 4.0Ah battery covers the target audience's actual lawn size. The 33cm deck manoeuvres into spaces where nothing wider can go. The near-silent running changes the mowing experience qualitatively-  without the noise, the chore becomes noticeably less of a chore.

The limitations are honest and mostly inherent to the cordless small-mower category rather than specific failures of this machine: 150m² is a real ceiling, push-only limits slope performance, the 32L bag needs regular emptying, and there is no rear roller for stripes. None of these come as surprises to the buyer who reads the specification before purchase — they are reasonable compromises for a compact, lightweight, budget-friendly machine designed for a specific and well-defined job.

For the small-garden homeowner who is still wrestling with a mains cable, or who is paying for annual petrol maintenance on a machine that runs for 20 minutes twice a week, the HY20CLM33 is a sensible, well-priced, and genuinely pleasant step up.

Review based on hands-on testing across three sessions in April–May 2026 on two privately owned UK gardens (65m² and 110m²). Specifications confirmed from Amazon UK product listing (ASIN B0GYFC2ZTQ), B&Q product listing, and The Green Reaper retailer listing, cross-referenced against Hyundai Power Equipment product documentation. Price reflects B&Q listing (~£139.99) and Amazon listing at time of publication (May 2026).