Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Understanding SAE J2474-2021: Battery Run-Time Testing for Self-Propelled Sweepers and Scrubbers
Overview and Scope
SAE J2474-2021 provides a uniform method for testing the battery run-time of electric self-propelled sweepers and scrubbers. The standard is intended for machines covered under SAE J2130-2 and aims to establish a consistent approach for evaluating how long a machine can operate under specified conditions before its battery must be recharged. This is crucial for manufacturers, fleet operators, and end users who need reliable performance comparisons.
By standardizing test cycles, environmental conditions, and battery conditioning, the standard ensures that run-time results are repeatable and representative of real-world usage patterns.
Key Definitions and Test Conditions
The standard defines several critical terms and conditions that must be adhered to during testing:
- Cleaning Mode: All brushes and brooms are in contact with the floor, cleaning solution flow is set to mid-range, dust control and pick-up systems are operating, and the machine is driven at an average cleaning speed.
- Transport Mode: Only the propulsion drive motor is active; all other systems are shut off. The machine travels at maximum transport speed.
- Cut-Off Terminal Voltage: The voltage point recommended by the battery manufacturer beyond which operation should cease to prevent damage.
- Battery Conditioning: Batteries must undergo between 10 and 100 charge/discharge cycles prior to testing to ensure stable capacity.
- Environmental Conditions: Both charging and testing must be performed within a temperature range of 15°C to 27°C.
Test Cycles at a Glance
| Machine Type | Test Cycle Details |
|---|---|
| Sweepers | 1 hour cleaning mode → 5 minutes transport mode → dump cycle. Repeat until cut-off voltage is reached. |
| Non-recycling Scrubbers | Run in cleaning mode until solution tank empties → 10-minute refill/drain stop. Repeat until cut-off voltage is reached. |
| Recycling Scrubbers | Run in cleaning mode with recycling system on for 2 hours → 10-minute refill/drain stop. Repeat until cut-off voltage is reached. |
Test Procedures and Reporting Results
The run-time test for sweepers follows a cleaning-transport-dump cycle that mirrors typical fleet operation. For scrubbers, the cycle emphasizes solution usage and refill intervals. The test concludes when the battery reaches its cut-off terminal voltage.
🛠️ Engineering Design Insight: The mixed cleaning and transport phases in the sweeper test impose varied loads on the battery, reflecting real-world energy demands. Designers can optimize battery systems by evaluating performance under both full auxiliary load (cleaning) and propulsion-only load (transport). Additionally, the ten-minute refill cycle in scrubber tests provides a built-in recovery period that may affect overall run-time results; this must be accounted for in battery sizing calculations.
⚠️ Common Mistake: Failing to condition the battery properly (fewer than 10 cycles) can lead to overestimating run-time, as the battery may not have reached its stable capacity. Always follow the prescribed cycle range and temperature control for valid results.
Results must be reported in the format specified in Section 7 of the standard, including run-time in hours, model name/number, ampere-hour rating of the battery used, details of optional equipment operating during the test, and the number of refill or dump cycles. For example:
Battery Run-Time Test Results Model: XYZ-2000 Ampere-Hour Rating: 24 Ah Run-Time: 3.5 hours Options: Power steering on, vacuum fan on Number of Refill Cycles: 12
Frequently Asked Questions
Q: How is the battery conditioned before testing?
A: The battery must be discharged and charged at least 10 times but no more than 100 times prior to the run-time test to ensure it reaches stable capacity.
Q: What environmental conditions are required?
A: The entire charging and testing process must be conducted within a temperature range of 15 to 27°C to ensure repeatability.
Q: What is the difference between cleaning and transport mode?
A: Cleaning mode operates all floor cleaning systems (brushes, brooms, dust control, water pick-up) at typical settings, while transport mode only uses the propulsion motor for travel.
Q: How should test results be reported?
A: The report must include run-time, model number, battery ampere-hour rating, options used, and the number of refill (for scrubbers) or dump (for sweepers) cycles. The standard provides a specific format for clarity.
Following SAE J2474-2021 ensures that battery run-time data for sweepers and scrubbers is reliable and comparable, supporting better design decisions and operational planning.
