Safety Standards for Mobile Phone Lithium Battery Chargers

1. Introduction

The safety of the charger cannot be determined only by checking the output characteristics, because good output characteristics cannot guarantee the reliability of the charger. Therefore, this standard stipulates that the comprehensive performance of the charger should be examined, including the safety requirements and structural design requirements for components such as transformers and power cords. The charger should ensure that it does not pose a threat to personal safety under fault conditions. In addition to electrical protection functions, the charger should also have fire protection functions. According to the requirements of similar products, the standard stipulates that its fireproof material level is V-2.

During the formulation process, this standard referred to relevant international standards, such as IEC62133, IEC61960, UL1642, UL2045, etc., and GB 4943-2001 "Safety of Information Technology Equipment" and other standards, and strived to make the standard clauses suitable for my country's national conditions and the test methods operable. During the preparation process, this standard followed the verifiability principle in the "ISO Technical Work Guidelines": that is, the specified technical requirements can be demonstrated by test methods. If there is no scientific method for testing or inspection, and if the exact test results cannot be obtained stably and reliably, such clauses will not be included in the standard.

2. Safety standards for mobile phone lithium battery chargers

2.1 AC input voltage

The rated input voltage of the charger is AC 220 V and the frequency is 50 Hz. To ensure safety, the charger should be able to withstand fluctuations in the mains power within a certain range. The voltage fluctuation range required by the standard is 85% to 110% of its rated value, and the frequency fluctuation range is ±2 Hz.

2.2 Power Cord Assembly

(1) The power cord assembly should comply with the requirements of GB2099;

(2) The rating of the power cord assembly should be greater than the rating required by the charger power supply;

(3) The cross-sectional area of ​​the power cord should not be less than 0.75 mm2;

(4) The power cord in the power cord assembly shall meet the following requirements:

* If the power cord is rubber insulated, it should be synthetic rubber and should meet the requirements of GB5013 for general rubber sheathed flexible cables;

* If the power cord is PVC insulated, it should meet the requirements of GB5023 for light PVC sheathed cords. 2.3 Isolation transformer

The safety isolation transformer should be constructed to ensure that no dangerous voltage will appear on the safety extra-low voltage winding when a single insulation fault and other faults caused by it occur. The isolation transformer should be tested in accordance with the relevant provisions of Appendix C of GB4943.

2.4 Instructions and labeling requirements

2.4.1 General requirements

Manufacturers should provide users with sufficient information to ensure that users will not cause dangers within the scope of this standard when using it according to the manufacturer's regulations. Standard simplified Chinese characters should be used. The mark should be durable and eye-catching and be able to withstand the mark durability test. First wipe it with a cotton cloth dipped in water for 15 seconds, then wipe it with a cotton cloth dipped in gasoline for 15 seconds. The label should be clear, should not be easily peeled off, and should not have curling edges.

2.4.2 Instructions

Manufacturers should provide necessary instruction manuals and remind users to pay special attention to situations that may cause danger during operation, maintenance, transportation or storage of the charger.

2.5 Structural design requirements

2.5.1 Stability

Chargers that are plugged directly into a wall socket and bear their weight on the pins should not subject the wall socket to excessive stress. Compliance can be checked by a socket stress test. The charger should be inserted into a fixed socket without grounding contacts as in normal use, and the socket can be rotated about a horizontal axis located 8 mm behind the socket mating surface and intersecting the center line of the pipe contact. The additional torque that must be applied to the socket to keep the mating surface vertical should not exceed 0.25 Nm.

2.5.2 Structural details

Reverse polarity connection and forced charging or discharging of batteries may cause danger, so measures should be taken in the design to prevent reverse polarity connection and forced charging or discharging. Short-circuit or open-circuit any protective components one by one, and force charging and discharging for 2 hours each. The charger should not catch fire or explode.

2.5.3 Accessibility (electric shock and energy hazards)

The charger should be touch-proof during normal use to prevent electric shock and energy hazards.

If the insulation of external wiring of an extra-low voltage circuit is accessible to operators, the wiring should be:

*Will not be damaged or subjected to stress;

*No operator contact required.

2.5.4 Connection and Wiring

(1) Chargers that use non-detachable power cords should be equipped with fastening devices:

*The wire is not subjected to stress at the connection point;

*The outer jacket of the wire is not subject to wear and tear; *The power cord should be able to withstand the tensile test. The power cord should withstand a stable tensile force of 30N for 25 times. The tensile force is applied in the most unfavorable direction. Each application time is 1s. The power cord should not be broken;

*The power cord fastening device shall be made of insulating material or of a bushing with insulating material that meets the requirements for additional insulation.

(2) The power cord entry opening should be equipped with a cord entry sleeve, or the cord entry or sleeve should have a smooth circular bell mouth with a radius of curvature at least equal to 1.5 times the outside diameter of the cord with the largest cross-sectional area to be connected.

The cord entry sheath shall:

* Designed to prevent the cord from being bent excessively when entering the charger;

*Made of insulating material;

*Use reliable methods to fix;

* The distance beyond the entrance opening of the charger shall be at least 5 times the outer diameter of the cord or, for a flat cord, at least 5 times the long dimension of the cross section of the cord.

2.6 Shell surface

When the user touches the battery casing, its temperature should not cause the user to react suddenly and injure him. People's reaction to temperature is not only determined by the degree, but also by the conductive properties and heat capacity of the casing material. A metal casing at 60°C feels hotter than a plastic casing at 70°C. The relevant standards of UL and IEC stipulate that the temperature rise of non-metallic casings shall not exceed 50°C, and the casings of most mobile phone batteries are made of non-metallic materials. Therefore, this standard draws on this regulation and requires the following: After the charger has been working for 2 hours at rated speed, if the surface temperature change of the casing is less than 1°C/h, the temperature is considered stable. At this time, the surface temperature rise of the casing should be less than 50°C.

2.7 Output short circuit protection

The charger should have an automatic short-circuit protection function. If the charger output is short-circuited, the charger should be able to automatically protect itself and automatically resume work after the fault is eliminated.

2.8 Insulation resistance

At room temperature, use an insulation resistance tester with a DC voltage of 500 V to test the primary circuit to the shell, the secondary circuit to the shell, and the primary circuit to the secondary circuit of the charger's main circuit. The insulation resistance of the charger should not be less than 2 MΩ. 2.9 Insulation strength

Use a withstand voltage tester to test the insulation strength of the charger, and the charger must be tested for insulation strength only after the insulation resistance test has been completed and meets the requirements.

The primary circuit to the enclosure and the primary circuit to the secondary circuit should be able to withstand an AC voltage of 50 Hz and an effective value of 1500 V (leakage current ≤ 10 mA), and the secondary circuit to the enclosure should be able to withstand an AC voltage of 50 Hz and an effective value of 500 V (leakage current ≤ 10 mA), and there should be no breakdown or arcing. The test voltage should be gradually increased from less than half of the specified voltage value and last for 1 min when it reaches the specified voltage value.

2.10 Requirements under abnormal operating and fault conditions

The charger design should be able to limit the risk of fire or electric shock caused by mechanical or electrical overload or failure, abnormal operation or improper use as much as possible. The transformer overload test is carried out in accordance with the requirements of Appendix C1 of GB4943. The following fault conditions can be simulated:

* Failure of any component in the primary circuit;

*Failure of any component in the secondary circuit.

2.11 Material flammability requirements

The materials used for the charger housing, printed circuit boards and components should be able to reduce the ignition hazard and flame spread to a minimum, and should be V-2 or better. When conducting heat resistance and fire resistance tests, V-0 grade materials can burn or scorch, but the duration of the burn does not exceed 5s on average. The hot particles or burning drops released during the burning will not ignite the absorbent cotton. V-1 grade materials can burn or scorch, but the duration of the burn does not exceed 25s on average. The hot particles or burning drops released during the burning will not ignite the absorbent cotton. V-2 grade materials can burn or scorch, but the duration of the burn does not exceed 25s on average. The hot particles or burning drops released during the burning will ignite the absorbent cotton. Toxic fumes may be emitted during this test. If applicable, the test can be conducted in a fume hood or in a well-ventilated room, but there should be no airflow that may invalidate the test results.

The test flame should be obtained by using a Bunsen burner. The inner diameter of the Bunsen burner tube is 9.5mm±0.5mm, and the length of the tube is about 100mm from the main air inlet. The Bunsen burner should use a gas with a calorific value of about 37MJ/m3. The flame of the Bunsen burner should be adjusted so that the Bunsen burner is in a vertical position, and when the air inlet is closed, the total height of the flame is about 20mm. The top of the flame should contact the sample and burn for 30s, then move the flame and stop burning for 60s, and then burn at the same position for 30s.

During the test, after the test flame is evacuated for the second time, the sample should not continue to burn for more than 1 minute, and the sample should not be completely burned out. 2.12 Free fall test

The charger is dropped freely from a height of 1m onto a hardwood surface three times, and there should be no cracks or other damage on the surface.

2.13 Damp heat test

The test method is carried out in accordance with the requirements of "Test Cb" in GB/T 2423.9-2001. The product is unpackaged, the test severity level is: temperature 40℃±2℃, relative humidity (93±3)%RH, and the test duration is 2 days. After the test, it should meet the requirements of 4.7.2.