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 circuit
- Dielectric voltage
- Isolation resistance
- Imbalanced charging
Image on the left: A device undergoing a 'temperature test' (photo credit: 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:
- Mold stress release
- Handle loading
- Strain relief
Image on the left: A device undergoing a 'vibration test' (photo credit: 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.