The useful question is whether the mower will finish your lawn without a charging break. A battery count on the box does not always answer that: some mowers run on one pack, while others need two fitted together.
The Bosch ROTAK18V2-38 uses two 18V batteries at the same time. The pair supplied with the kit is one working set, so you will not have a spare simply because the box contains two batteries. That matters when you compare the price of the kit with the bare mower.
I bought the bare mower because I already had compatible batteries and a charger. If you are starting from scratch, the kit is the more useful comparison. Here is how I would work out whether that setup suits your lawn and mowing routine.
The area claim is a starting point
Bosch specifies the ROTAK18V2-38 with a 38 cm cutting width, 40 litre grass box, a recommendation of at least 4.0 Ah batteries and a maximum recommended lawn area of 500 m². Its mower manual explains that cutting capacity changes with grass density, moisture, length and height of cut; frequent stops and starts also reduce it. The 500 m² number is therefore a comparison under specified conditions, not a universal runtime estimate.
For a 200 m², regularly cut lawn, the stated maximum gives room on paper. For a 480 m² lawn with slopes, wet patches and long grass after a holiday, buying on the headline alone is risky. Map the area of grass rather than the whole garden, and remember that beds, paths and borders break up the cutting route.
Why “two 18V batteries” matters
Its 38 cm cut is manageable around borders, and the folding handle helps with storage. I choose between the kit and bare model by what batteries are already in the shed, then allow for the whole mowing session. Both fitted batteries work together; the second one is not a spare to swap in later.
This model uses two 18V batteries together to deliver 36V system performance. A pair in the mower is one working set. Two batteries supplied in a kit are not automatically a spare set: both are needed to mow. If uninterrupted cutting is crucial on a large lawn, check the cost and compatibility of a second pair, or choose a mower and power system with more comfortable capacity.
The Bosch UK kit identified as 06008B9M70 includes two PBA 18V 4.0Ah batteries and an AL 2x18V-88 charger. The bare 06008B9M02 listing excludes batteries and charger; it includes an extra blade. The verified Amazon listings for the two-battery mower kit and the bare mower describe different supplied contents, so compare the retailer’s current package against Bosch’s order number before paying.
Do not compare a 4.0Ah number with a different voltage system as if the capacities were interchangeable. A battery must fit the tool and meet the maker’s guidance; check both the connector family and the pair required. An existing 18V Bosch battery from another compatible tool can be useful, but one battery on its own does not complete this two-battery mower setup.
Estimate your own job before buying
- Measure only the lawn. A 10 m by 12 m rectangle is 120 m²; subtract beds and paving, then add separate grass sections.
- Note whether you normally mow weekly or let growth get ahead. Long or damp grass will cut more slowly and may demand a higher first pass.
- Compare the result with the manufacturer’s maximum as a ceiling, not a guaranteed usable target.
- If close to that ceiling, price the complete battery setup and consider a wider machine or another power source.
For instance, a 10 m × 12 m lawn with 20 m² of beds contains 100 m² of grass. That arithmetic gives the right area to compare, but it cannot predict exact minutes of runtime. Cutting height and grass condition still matter. Bosch’s guide also recommends avoiding excessive one-pass height reductions; follow the mower manual for safe operation.
Check what “ready to mow” means in your shed
Put your existing batteries and charger together before deciding that a bare tool is the bargain. Check the battery family, suitable capacity and how many the mower needs to run. A compatible drill battery can be useful, but one pack will not complete this mower’s required pair.
Think about the whole mowing session too. If you use the same battery system for a trimmer or blower afterwards, those jobs draw on the same stock of charged packs. The mower finishing the lawn is only part of having enough power to finish the garden.
For a routinely cut lawn well within the maker’s area guidance, one charged working set may be enough. If you are close to the advertised area or regularly tackle longer growth, give yourself more headroom. A second compatible pair adds cost as well as convenience.
I would not turn an “up to” area into a promised runtime. Buy for the grass and routine you actually have. It is usually easier to keep a small lawn under control with regular cuts than to ask a compact mower to recover several weeks of growth in one go.
When a different mower is the better buy
If access and storage are tighter constraints than battery capacity, my guide to choosing a mower for a small garden works through gates, turning space and where the machine will live.
For a narrow garden with many corners, a smaller cutting deck may be easier to manoeuvre even if a larger mower carries more battery capacity. For a broad lawn near the 500 m² stated maximum, the ROTAK18V2-38 kit can be a sensible candidate only after accounting for actual mowing conditions and the cost of any spare battery pair.
Compare cutting width, power system and storage against our cordless mower buying guide. If stripes are the priority, check our rear-roller mower guide separately: a conventional rotary mower’s deck width is not a stripe system. The best purchase is the complete mower-and-battery setup that fits your lawn, not just the largest advertised area on a box.
Sources and specification checks
Manufacturer specifications checked 19 September 2026. Check current retailer variant and terms. Featured image is an AI-generated illustrative scene, not a product test photograph; supporting graphics are original.
