Roborock S4

The Roborock S4 had a specific mission when it launched in 2019: be a great vacuum-only robot at a reasonable price. No mopping, no fancy gimmicks—just solid cleaning for people who wanted Roborock’s excellent LiDAR navigation without paying for features they’d never use. That focused approach made it appealing, though one significant design flaw would eventually overshadow its strengths.

The Short Version

This robot excels on hard floors and low-pile carpet, where its 2000 Pa suction and 19 CFM airflow make quick work of everything from sand to cereal. The LiDAR navigation remains accurate even by 2025 standards, mapping efficiently in complete darkness and avoiding random bumping patterns. However—and this is a big however—the S4 sits so low to the ground that medium or high-pile carpet can cause the drivetrain to struggle, triggering error messages and failed cleaning runs.

Finding one now means hunting through eBay, Mercari, or Facebook Marketplace, where used units typically sell for $80 to $150 depending on condition.

What Makes It Tick

Suction and Cleaning Power

The S4 pulls 2000 Pa of suction through a bristle/rubber combination brush that floats to maintain contact with the floor. At roughly 19 CFM of airflow—impressive for its generation—it handles sand, rice, and pet hair effectively on hard surfaces.

The 420ml dustbin sounds modest, but remember: this robot doesn’t have a mopping tank eating into its capacity. Pet households will still need to empty it every run or two.

One nice touch: the single 5-arm silicone side brush resists hair tangling far better than the older bristle designs.

Navigation That Still Holds Up

LiDAR navigation was the S4’s main selling point, and it hasn’t aged poorly. The robot maps your home methodically, following a Z-shaped pattern with perimeter cleanup rather than bouncing randomly like cheaper models. It works flawlessly in pitch darkness (unlike camera-based robots) and tracks its position in real-time through the app.

A January 2021 firmware update added support for up to 4 floor maps, addressing early complaints about multi-story homes. You can edit rooms, set no-go zones, and schedule specific areas—features that felt premium in 2019 and remain useful today.

The catch? Mirrors confuse the LiDAR, sometimes creating “phantom rooms” on your map. And without a front-facing camera or 3D sensors, the S4 won’t recognize objects. Cables, socks, and small toys will get run over or dragged around. Keep your floors tidy.

Battery Life

The 5200 mAh lithium-ion battery delivers up to 150 minutes on quiet mode or around 120 minutes at max power. That translates to roughly 2,700 square feet of coverage per charge under ideal conditions. Charging takes 4-5 hours.

Physical Dimensions

At 13.8 inches round and 3.8 inches tall (including the LiDAR turret), you’ll need more than 3.8 inches of clearance for it to fit under furniture. The robot weighs about 8 pounds.

The Carpet Problem

Here’s where the S4’s story takes a frustrating turn. Roborock positioned this robot low to the ground—presumably to maximize suction seal—but the result is only 15mm (about 0.6 inches) of threshold clearance. That’s not enough.

On medium or high-pile carpet, the robot’s underbelly drags against the fibers. The wheels lose traction. The system detects excessive motor strain. You get Error 8 (stuck) or Error 5 messages in places where other robots clean without issue.

This isn’t fixable through firmware updates. It’s baked into the hardware design. Roborock eventually released the S4 Max specifically to address this, giving it higher ground clearance while keeping the same core features. If you have anything thicker than commercial-grade low-pile carpet, the original S4 simply isn’t the right choice.

Filtration and Noise

The washable E11 high-efficiency filter isn’t true HEPA, but it captures fine particles adequately for most households. Plan on replacing it periodically—about $30 for a 2-pack of official filters or $15 for a 4-pack of third-party alternatives.

Noise levels range from around 60 dB on silent mode to 72 dB at maximum. That’s louder than conversation but quieter than a traditional upright vacuum.

App Experience

The Roborock app (also compatible with Mi Home) earns consistently high ratings—around 4.7/5 on iOS. Map stability and connection reliability are particular strengths. You get four cleaning modes (Silent, Balanced, Turbo, Max), zone cleaning, room selection, and custom scheduling.

Voice control works through Amazon Alexa and Google Assistant. Matter and HomeKit compatibility? No. Remote camera viewing? Also no—there’s no camera.

The robot needs Wi-Fi for mapping features and remote control, but you can press the physical button to start a basic cleaning run without any network connection.

Maintenance and Longevity

The S4 is straightforward to maintain. End caps on the brush roll pop off for easy hair removal. The dustbin lifts out from the top. Clean the cliff sensors regularly to avoid Error 4 warnings—these four sensors are quite sensitive and may refuse to cross black rugs or dark patterned carpet.

For repairs, the battery uses standard 18650 cells in a custom casing, accessible through screws. The LiDAR motor tends to fail after 3-4 years (Error 1), but replacement parts cost around $20 online.

Parts availability remains excellent since the S4 shares filters and brushes with the popular S5, S6, and S5 Max series. Amazon and AliExpress both stock them.

All original warranties have expired, though Roborock’s email support still handles troubleshooting questions. For repairs, you’re looking at DIY or out-of-pocket costs. The r/Roborock subreddit has accumulated deep knowledge on common fixes.

Who Should Consider It

The S4 makes sense in one specific scenario: you’ve found one for under $100 and your home has hard floors or very low-pile commercial carpet. Under those conditions, you’ll get LiDAR navigation accuracy comparable to 2025 models at a fraction of the cost.

For everyone else—especially anyone with medium or thick carpet—look elsewhere. The Roborock Q5 serves as the modern spiritual successor: vacuum-focused, no mopping distractions, but with auto-empty dock compatibility and proper carpet climbing ability. If you absolutely want an older Roborock, the S4 Max fixed the clearance issue while keeping everything else intact.

Original Package Contents

When sold new at $399, the box included:

• Roborock S4 robot
• Charging dock with power cable
• Cleaning tool (stored in a compartment under the hood)
• User manual
• Sometimes a spare filter, depending on region

Specifications at a Glance

Feature	Specification
Suction	2000 Pa
Airflow	~19 CFM
Dustbin	420ml
Battery	5200 mAh Li-ion
Runtime	Up to 150 min (quiet mode)
Coverage	~2,700 sq ft per charge
Navigation	LiDAR
Floor Maps	Up to 4
Height	3.8 inches
Threshold Climbing	15mm (~0.6 in)
Mopping	No
Self-Empty	No
Voice Control	Alexa, Google Assistant
Wi-Fi	2.4 GHz
Filter	E11 (washable)
Color	Black (glossy)

Common Confusion

A few points that trip people up: the S4’s dustbin holds 420ml, not 460ml (that’s the S4 Max). Some sources list the height at 3.5 inches, but official specs and actual measurements put it at 3.8 inches at the LiDAR tower. And while early reviews mentioned single-floor mapping only, later firmware added multi-floor support—so newer reviews are more accurate on this point.