WHY IS THE ADOPTION OF A DEVICE SAFETY STANDARD NECESSARY?
The number of fires caused by motorised PMDs has increased in the past few years, with more than 90 fire incidents involving PMDs since 2016. As PMDs only started gaining popularity in recent years, many of the motorised PMDs used do not conform to any reliable safety standards. The adoption of a safety device standard is therefore necessary to ensure the safe use of such devices.
LTA carefully studied the safety standards available and determined that the UL2272 standard is most suitable for the common types of motorised PMDs used in Singapore, such as electric scooters (e-scooters), self-balancing hoverboards and electric unicycles.
Incidents of PMD-related fires over the last few years (photos credits from Singapore Civil Defence Force's Facebook)
WHY WAS UL2272 CHOSEN OVER OTHER STANDARDS?
It is often difficult to determine the exact cause of the fires due to the extent of fire damage to the PMDs involved. However, based on literature reviews and consultations with the Singapore Civil Defence Force (SCDF), PMD fires may be caused by an electrical anomaly to the electrical circuitry or batteries, which could result from various factors, but not limited to, physical damage to the device, overcharging of rechargeable batteries, use of an unsuitable charger/battery, or manufacturing defects.
UL2272 is assessed to be a suitable safety standard as it evaluates PMDs from a system-level perspective, which better anticipates the full spectrum of usage conditions of the entire PMD, instead of just assessing individual components of a device.
Getting a device certified for UL2272 requires passing a series of electrical, mechanical and environmental tests. Its testing parameters are based on several components like the electrical and mechanical factor for safety, as well as the impact of environmental factors such as exposure to water.
Evaluation tests for UL2272 can be broadly classified into 3 categories as follows:
1. ELECTRICAL TESTS
Electrical tests typically cover a range of tests:
Short CircuitOver-chargeOver-dischargeTemperatureDielectric VoltageIsolation ResistanceImbalanced Charging
A device undergoing a ‘temperature test’ (Image courtesy of SGS Testing & Control Services)
A temperature test typically determines whether a device’s battery cells and critical components are able to withstand specific operating current, voltage and temperature limits during charging and discharging conditions, e.g. when the device is in use/operation.
2. MECHANICAL TESTS
Mechanical tests typically cover a range of tests:
VibrationShockCrushDropMold Stress ReleaseHandle LoadingStrain Relief
A device undergoing a ‘vibration test’(Image courtesy of TUV Rheinland)
A vibration test evaluates the device’s ability to withstand vibration that may occur during its anticipated use. Device would be subjected to vibration in each axis for a stipulated period of time depending on the number of samples submitted.
3. ENVIRONMENTAL TESTS
Environmental tests typically cover a range of tests:
Water Exposure (IPX4/ Partial Immersion)Thermal Cycling
A device undergoing an 'IPX4 test'. (Image courtesy of SGS Testing & Control Services)
During an ‘IPX4 test’, water is sprayed on devices from all directions using a rotating sprinkler system for 10 minutes to simulate rain and splashing of water. Following the test, device will be placed under an observation period to ensure that there is no explosion, fire, rupture, electrolyte leakage and shock based on the stipulated testing parameters.
PMD models that have been awarded the UL2722 certification must also undergo regular factory inspections to verify that device production continues to comply with requirements under the UL2272 standard. Manufacturers who persistently do not demonstrate adherence to the standard and take subsequent actions to ensure that their production line adheres to the standard may have their certification cancelled.
Article credits from LTA website - ul2272 standard for personal mobility devices (pmds)