Security Robot Battery: Runtime and 24/7 Availability

Plant managers evaluating a security robot battery read the datasheet first. It states a number in kWh or a peak runtime under ideal conditions. That number is operationally irrelevant. What counts in operation is how many perimeter kilometres get driven per 24 hours under real sensor load, at real outside temperature, with what reserve buffer for alarm dispatches. This article works through the numbers for the QR-2 and names the precondition for uninterrupted 24/7 coverage.

Security robot battery: what runtime means operationally

Runtime is not a function of battery capacity in kWh. Runtime is distance performance per charge cycle under real load. Real load means: thermal stream active, LiDAR scan continuous, cellular and LTE backhaul transmitting, drive at 4 km/h average across gravel, asphalt and light gradients.

Under these conditions the QR-2 runs 6 to 8 hours of active patrol per charge. The spread results from topography and weather. On a level industrial-park site with asphalt paths the value sits at the upper end. On hilly plant terrain with gravel sections at the lower end.

The relevant metric for the procurement decision is not this peak runtime but availability per 24 hours. A charging cycle is not downtime, it is a planned part of the patrol schedule. Plant managers must calculate runtime against the actual path network and required patrol frequency, not against abstract hours. A 12-kilometre perimeter with frequency every 30 minutes in the high-risk zone has a different energy budget than a 4-kilometre perimeter with frequency every 2 hours.

The framework for autonomous mobile machinery is set in EU Machinery Regulation 2023/1230, including requirements for energy and charging systems. Safety requirements for mobile platforms follow EN ISO 13482.

Next step: review the technical baseline in the QR-2 specification.

Charge cycle and autonomous docking station

The QR-2 docks at the charging station automatically once residual capacity reaches 20 percent. The full charge from 20 to 95 percent takes 90 minutes at 3.5 kW charging power. The station does not charge to 100 percent, because the last 5 percent stress cell lifetime disproportionately and deliver no relevant range gain.

The docking station requires 1.5 m² of covered location with a 230 V/16 A connection. Frost-free conditions are not strictly required, because the integrated battery heater activates below 5 degrees. For outdoor installation a protective roof against direct precipitation must be in place.

During the 90 minutes of charging time, in tandem operation the second robot takes over the critical sectors. In solo operation that time is a scheduled patrol pause. The charging process produces no sound emissions above 45 dB(A), measured at 3 metres distance, and is suitable for night operation near residential areas.

The station itself is part of the Robotics-as-a-Service model and is delivered without separate CapEx.

24/7 availability: one robot or tandem

A single QR-2 achieves 16 to 18 hours of active patrol in 24 hours, with 6 to 8 hours of charging time spread across two or three charge cycles. That is an availability of 66 to 75 percent, measured by patrol time per day.

For uninterrupted 24/7 coverage without any patrol pause, two robots in staggered charge cycle are required. While robot A patrols, robot B charges. After 6 hours the roles swap. Patrol frequency in the perimeter stays constant.

The tandem configuration costs 7,000 euros monthly in the RaaS model. It replaces three guard shifts with personnel costs between 15,000 and 25,000 euros, depending on collective agreement and location (source: BDSW industry statistics). The data basis for hourly rates and availability ratios in stationary Wachschutz is provided by the BDSW industry statistics.

Plant managers choose the configuration by risk class. Tandem for KRITIS-relevant sectors with requirements from the KRITIS-Dachgesetz (KRITIS Umbrella Act) and specifications from the BBK on physical protection. Solo for secondary perimeters with lower frequency requirement. The patrol plan is parametrised centrally in the Quarero control room. Coordination with the shift changes of the plant fire brigade ensures handovers are documented.

Comparison figures are available at Wachschutz cost comparison.

Temperature, weather and battery degradation

At minus 15 degrees, runtime drops by 18 to 22 percent compared to 20 degrees ambient [internal measurement data Quarero Robotics, available on request]. The effect comes from reduced ion mobility in the cell, not from the drive. The battery heater activates automatically below 5 degrees and is included in the monthly RaaS price, with no surcharge for locations in southern Germany, northern Germany or higher altitudes.

The lithium iron phosphate cells (LFP) used retain 80 percent of their initial capacity after 3,000 full cycles (see NREL Battery Lifetime Analysis). At two charge cycles per day this corresponds to a calendar lifetime of roughly four years to the degradation limit. Quarero replaces the battery pack preventively after 24 months in the RaaS model, at no extra cost to the operator. The exchange happens during the quarterly maintenance and causes no additional downtime.

In heavy rain, storm and snowfall, runtime stays within the specified tolerance of 5 percent. The drive reduces maximum speed to 3 km/h on wet surfaces, which slightly lowers energy consumption per kilometre and compensates the weather effect. LFP cells are markedly more robust against thermal events than NMC cells, which in a security application is an operational argument alongside lifetime.

Patrol plan and energy budget

Energy consumption per kilometre is 180 to 220 Wh, depending on gradient and surface. Level asphalt: 180 Wh/km. Gravel with 3 percent gradient: 220 Wh/km. Thermal stream and LiDAR add a constant 90 W to drive power, independent of speed. While stationary to verify a thermal signature, the robot continues to consume those 90 W plus 30 W for radio and compute load.

Plant managers define patrol frequency per sector. High-criticality areas such as transformer station, tank farm or server room outer wall get frequency every 30 minutes. Secondary areas such as staff car park or storage yard every 2 hours. The algorithm prioritises by risk score and adjusts the route dynamically when residual capacity drops. Secondary sectors get stretched, critical sectors stay on full frequency.

A reserve of 15 percent battery is always reserved for unplanned alarm dispatches. If the plant security control system reports a motion alarm at a distant fence section, the robot draws from this reserve and drives directly to the point. The planned route does not need to be aborted. Incident data from the past 90 days feeds into the weekly patrol plan optimisation. Sectors with recurring events get higher frequency, low-event sectors get unburdened.

Methodological detail on route calculation is at perimeter protection for industrial parks.

Availability compared to stationary Wachschutz

A guard post costs 15,000 to 25,000 euros monthly for 24/7 coverage at a single point. The range comes from collective-agreement binding under Manteltarifvertrag, region and qualification level under §34a GewO. A QR-2 covers up to 64 km of perimeter per day at 4 km/h and 16 hours of active patrol. For a typical industrial-park perimeter of 8 km that equals eight rounds per day. In tandem operation the average frequency is significantly higher.

Human availability sits at around 75 percent of paid hours due to sick leave, vacation, breaks and shift handovers (source: BDSW industry statistics). That is not an accusation against Wachschutz, it is a consequence of labour-law reality. The security-robot battery system reaches a documented availability of 96 percent over 12 months [internal operational data Quarero Robotics, available on request]. Downtime for maintenance is 4 hours per quarter, schedulable outside critical shifts.

The comparison is not "robot replaces human". The comparison is: the robot takes over the repetitive patrol task, the human post concentrates on access control, Sachkundeprüfung-relevant interventions and actions only a human can perform. The hybrid calculation for a typical industrial park is worked through in the hybrid TCO analysis industrial park.

RaaS model: battery risk does not sit with the operator

In the Robotics-as-a-Service contract, Quarero carries the entire hardware risk. Battery degradation, cell exchange after 24 months, defect of a drive motor, failure of the charging station: all these events are cost-neutral for the operator. The monthly fixed price of 3,500 euros for a QR-2 includes battery exchange, quarterly maintenance and a replacement unit on defect with delivery within 48 hours.

The operator pays no CapEx. There are no acquisition costs for the robot, no investment in the charging station, no hidden costs for battery pack renewal in the third year of operation. The contract runs for 24 months, then monthly cancellable with 30 days notice. Delivery and commissioning happen within 48 hours of contract signature.

This structure shifts CapEx risk from the plant manager to the manufacturer. For internal approval in plant controlling, this is an OpEx item in the same order of magnitude as an existing Wachschutz contract. Technical obsolescence sits with the supplier, not the operator. The price tiers are documented in the three-tier pricing model.

Operational checklist for the plant manager

Six steps need to be worked through before the procurement decision.

First: measure perimeter length in kilometres. Not the fence line, but the actual patrol path, which depends on gate installations, dead ends and sectoral frequency. Multiply the value by the desired patrol frequency to derive daily kilometres. From this follows the configuration question solo or tandem.

Second: define the location for the charging station. Covered, 230 V/16 A, frost-free or with battery heater. The station should sit centrally in the patrol network so that empty runs to docking are minimised. One station per robot, in tandem operation two physically separate stations for redundancy.

Third: define risk class per sector and parametrise the patrol plan in the control room. This classification follows the internal protection-need analysis, for KRITIS operators the requirements from the KRITIS-Dachgesetz (Bundestag-Drucksache 20/9262).

Fourth: check tandem operation if uninterrupted 24/7 coverage without a 90-minute pause is required. A single robot does not deliver continuous patrol, it delivers patrol with scheduled charging windows.

Fifth: document the interface to plant fire brigade and control centre before commissioning. Who receives alarms, who acknowledges, who escalates? The answer belongs in the operations manual, not in later improvisation.

Sixth: use a 30-day pilot to validate real runtime against the datasheet. The numbers in this article are derived from real deployments, but every plant site has individual topography, individual path network and individual weather. The pilot delivers the reliable basis for the scaling decision.

The next concrete step is technical pre-validation at the operator's own site. The QR-2 specification contains the baseline data for comparison with the plant site. For the 30-day pilot with documented runtime measurement: request pilot operation.