Battery Certification

What is the battery testing and certification?

A battery is defined as a composite container filled with a type of electrolyte and metal electrodes to generate current. It’s a device that converts chemical energy into electric energy. A battery has positive and negative electrodes. With the development of science and technology, a battery is defined as any small device that generates electric energy. For example, solar batteries. Battery performance parameters mainly include electromotive potential, capacity, specific energy, and resistance.

Although there are various approaches to classify batteries, it generally falls into three major categories.

• Category I

  Based on the type of electrolyte. This includes:

  • Alkaline batteries.
  • Electrolytes which are dominated by an aqueous solution of potassium hydroxide: for example, alkaline zinc-manganese dioxide batteries (also known as alkaline manganese batteries or alkaline batteries), nickel-cadmium batteries, nickel-metal hydride batteries, etc.
  • Acid batteries, in which sulfuric acid aqueous solution serves as the dominant medium, such as zinc manganese dioxide dry batteries (referred to as acid battery by some customers).
  • Seawater batteries.
  • Organic electrolytic batteries, in which organic solution serves as the leading medium, such as lithium battery and lithium-ion battery.

• Category II

  According to the working nature and storage mode, it includes:

  • One-shot batteries, also known as primary batteries, namely, the batteries that cannot be charged, such as Zn-Mn dry batteries.
  • Secondary batteries, namely rechargeable batteries, such as Ni-MH batteries, lithium-ion batteries, and nickel-cadmium batteries; accumulators are usually referred to lead-acid batteries, also secondary batteries.
  • Fuel batteries, which are characterized by the continuous addition of active materials to the cell from outside only when the cell is operating, such as hydrogen-oxygen fuel cells.
  • Reserve batteries, namely the battery does not directly contact with the electrolyte amid storage, until it is in use, such as magnesium-silver chloride batteries, also known as seawater batteries, etc.

• Category III

  Based on the materials of positive and negative electrodes of batteries, it includes:

  • Zinc-based batteries, such as Zn-Mn batteries and zinc-silver batteries.
  • Nickel-based batteries, such as Cd-Ni batteries and nickel-hydrogen batteries.
  • Lead-based batteries, such as lead-acid batteries.
  • Lithium-ion batteries, Li-Mn batteries; manganese dioxide-based batteries, such as Zn-Mn batteries and alkaline manganese batteries.
  • Gas (oxygen-based) batteries, such as Zn-O2 batteries.

Batteries are generally classified as dangerous products. As dangerous products, batteries usually require testing reports or certificates during transport or export processes. The common ones include the MSDS or appraisal report for air transport, which is required during transport. The others include CE and FCC certificates, which exporters may require for the export of products to the EU or for customs inspection.

Of course, many customers are concerned about safety issues for battery products. Battery safety testing is essential and common standards are as follows:

• GB/T 18287-2000
  General specification of lithium-ion battery for cellular phone
• IEC 62281-2004
  Safety standards for the transport of lithium batteries
• EN/ IEC62133
  Safety standards for lithium batteries
• UL 1642-2005
  Standards for lithium batteries
• UL 2054-2005
  Standards for domestic and commercial batteries
• GB 31241-2014
  Lithium-ion cells and batteries used in portable electronic equipment―Safety requirements

Common battery safety testing includes: continuous low-rate charging, vibration, high-temperature mold shell stress, high and low-temperature cycle, reverse charging (nickel battery), external short circuit, free fall, mechanical impact, thermal abuse, crush, low pressure, overcharge (nickel and lithium batteries differ) forced discharge, and high-rate charging.

What are the standards for battery testing?

Cell phone batteries and portable chargers used in our daily lives are sustainable rechargeable batteries. The service life of these batteries is reduced by usage. Thus, cycle life tests are also conducted when the battery is tested for quality.

As all major malls, e-malls, and franchised stores have set up higher requirements upon product inspection and certification. For example, Tmall, the famous e-mall in China, requires some products to pass international quality inspections. This requirement mainly involves the addition and modification of the entry qualification for nine major categories of products, namely, domestic appliances, 3C digital products, cosmetics, food, and health care products, shoes and bags, services, electronic tickets and certificates, sports & outdoor, and costume.

Looking further into the requirements needed for 3C digital accessories: The following products shall come with quality reports (at least one quality report issued by the third authority shall be provided for each brand, and the content of the finished product inspection must contain the brand name, product name, product code, and all testing items required for various types of products). The testing items required are as follows:

1. Power adapter: Testing items must include: labels, manual inspection (including label wiping and content inspection), and dielectric strength
2. Lithium battery: Testing items must include: discharge performance, free fall, overcharge protection, short and circuit test
3. Portable power source: Testing items must include: marks and notes, drop tests, discharge performance, power adapters, portable power sources to be tested as per GB4943, and lithium batteries to be tested as per GB18287.

After entering the platform, all stores shall apply for adding brands and categories, following the same standard stated above. For those that have settled on the platform, Tmall will conduct selective inspection on an irregular basis, so records shall be kept properly for possible inspection. If some goods that fail to pass relevant inspections are still sold in the market, not only do these products come with no quality guarantee, but they may also cause physical damage to customers. At present, all products are allowed to enter Tmall only after they have passed appropriate inspection. Quality reports not only serve as qualifications for entering renowned malls but also bring the products to a higher level, so that customers can rest assured to buy and use your products. This adds an additional guarantee to the products, and also makes them more trustworthy. According to this new rule, we particularly roll out one effective countermeasure:

Applicable products: Power adapters, portable power sources, laptop power sources, emergency chargers, backup power of iPhone/iPad, MP3/MP4 chargers, digital camera chargers, etc. Inspection items include Tmall’s inspection requirements, and the circuit structure assessment as well as discharge current testing of lithium batteries as required in the implementation standard GB4943-2001.

Very similar to T-Mall, NexPCB also implements similar inspection techniques for our 3C digital accessories. This includes

1. Power source adapters: Testing items include label, manual and dielectric strength. GB4943 must be conducted.
2. Lithium batteries: Testing items include discharge performance, free fall, overcharge protection, and short circuit test GB18287 must be conducted.
3. Portable power sources: Testing items include marks and notes, fall tests, and discharge performances. GB4943 must be conducted.

What are the methods to test batteries?

Testing methods of batteries and battery packs

1. What are the leading performances of secondary batteries (rechargeable batteries)?

Voltage, internal resistance, capacitance, internal pressure, rate of self-discharge, life cycle, battery sealing performance, safety performance, storage performance, appearance, etc., and also its performance during overcharge and over-discharge, its weldability, corrosion resistance, etc.

2. What electric indicators do cellphone batteries have? How can they be measured?

Batteries have many electric indicators, and only the most important characteristics are described here:

1. Battery capacity
   This indicator shows how much energy can be stored in a battery, which is measured in mAH. For example, 1600 mAH means that a battery can be discharged at 1600 mAH for one hour.

2. Life span of a battery
   This indicator displays the number of cycles in which a battery undergoes charge and discharge.

3. Internal resistance of a battery
   As mentioned above, the less the internal resistance of a battery, the better. However, such resistance cannot be zero.

4. Upper limit protection for battery charge
   To charge a lithium battery, there is a rated value for the upper limit that should not be exceeded by the voltage of such battery under any circumstances. The value is set by the IC adopted by the PCB.

5. Lower limit protection for battery discharge
   To discharge a lithium battery, there’s a preset limit. The voltage of the battery should not be lower than this rated value. The value is also set by the IC adopted by the PCB board.
   When the battery of a cellphone is discharged to a certain voltage that is just above its lower limit protection, the cellphone would automatically turn off due to a low battery level.

6. Short circuit protection of a battery
   When naked positive and negative electrodes of a battery are short-circuited, the IC on the PCB board shall immediately identify such a scenario and shut off MOSFET. When the breakdown has been solved, the battery can immediately supply electricity again. All these rely on the identification and action of the IC on the PCB board.

3. What are the reliability testing items of a battery?

• Cycle life
• Discharge characteristics at different rates
• Discharge characteristics at different temperatures
• Charge characteristics
• Self-discharge characteristics
• Self-discharge characteristics at different temperatures
• Storage characteristics
• Over-discharge characteristics
• Internal resistance characteristics at different temperatures
• High-temperature test
• Temperature cycle test
• Drop test
• Vibration test
• Capacity distribution test
• Internal resistance distribution test
• Static discharge test ESD

4. What are the safety testing items of a battery?

• Internal short circuit test
• Continuous charge test
• Overcharge
• Large current charge
• Forced discharge
• Drop test
• Free fall
• Penetration test
• Crush test
• Cutting test
• Low-pressure test
• Thermal abuse test
• Immersion test
• Burning test
• High voltage test
• Baking test
• Electronic oven test

5. What is the self-discharge of a secondary battery? What are the theself-discharge rates for various types of batteries?

Self-discharge, also known as charge retention capacity, refers to the ability of a battery to retain its stored charge under certain environmental conditions in an open-circuit condition. Generally speaking, self-discharge is mainly affected by the manufacturing process, materials, and storage conditions. The storage condition is one of the primary parameters to measure battery performance. In general, the lower the storage temperature is, the lower the rate of self-discharge. However, it should be noted that if the temperature is either too low or too high, the battery will be damaged. BYD ordinary batteries shall be stored at a temperature ranging from -20℃ to 45℃. A certain degree of self-discharge is normal after the battery is fully charged and left as an open circuit. According to the IEC standard, when Ni-Ca and Ni-MH batteries are left as an open circuit for 28 days at 20℃ and 6520% humidity after being fully charged, they will deem qualified if their 0.2C discharging duration is greater than 3 hours and 3 hours and 15 minutes, respectively.

Compared with other rechargeable battery systems, solar batteries containing liquid electrolytes have a notably lower self-discharge rate, around 10% per month at 25℃.

6. What is a 24-hour self-discharge test?

Self-discharge of a lithium battery shall be tested as follows: In general, 24-hour self-discharge is adopted to quickly test the charge retention capacity of the battery. Discharge the battery at 0.2C to 3.0V, charge it to 4.2V at 1C in CC-CV mode, with a cut-off current of 10mA, and after leaving it for 15 minutes, discharge it to 3.0V at 1C to measure its discharge capacity C1. Then charge the battery at 1C to 4.2V in CC-CV mode, with a cut-off current of 10mA, and after leaving it for 24 hours measure its discharge capacity C2 at 1C, and C2/C1*100% should be greater than 99%.

7. What is the internal resistance of a battery, and how to measure it?

The internal resistance of the battery is the resistance to the current flowing inside the battery when it is in operation. Generally, it is divided into AC internal resistance and DC internal resistance. As a rechargeable battery has a very small internal resistance, electrode capacity is polarized to generate polarized internal resistance during measuring DC internal resistance; as a result, its true value cannot be measured. However, the influence that polarized internal resistance can be eliminated when its AC internal resistance is measured, and therefore the actual value can be measured out.

AC internal resistance can be tested with the following methods. By using the feature that a battery amounts to an active resistor, input the battery to a constant current of 1000HZ,50mA, conduct sampling, rectification, filtering, and other operations upon the voltage, and then precisely measure its resistance.

8. What is the difference between internal resistance in the charge state and discharge state?

Internal resistance in the charge state refers to the internal resistance of the battery when it is 100% fully charged, while the internal resistance in the discharge state refers to the internal resistance of the battery when it is fully discharged.

Generally speaking, internal resistance in the discharge state is less stable and larger, while the internal resistance in the charge state is smaller and relatively stable. During the use of a battery, only the internal resistance in the charging state is of practical significance. In the later period of its use, internal resistance may increase to a certain level due to depletion of the electrolyte and the decrease in the activity of the chemicals inside.

9. What is a typical IEC cycle life test?

According to IEC, a typical cycle life test of a lithium battery is as follows:
After a battery discharge at 0.2C to 3.0V, recharge it at 1C in CC-CV mode to 4.2V, with a cut-off current of 20mA, leave it aside for one hour, and discharge it at 0.2C to 3.0V (one cycle).
After undergoing 500 cycles, its capacity shall be over 60% of the initial capacity.

10. What is a typical overcharge test?

According to IEC, a typical overcharge test of a lithium battery is as follows:

1. Discharge the battery at 0.2C to 3.0V
2. Set a 10V at current I, and charge the battery for time T (T=2.5*C5/I)
3. As a result, the battery shall not catch fire or explode.

11. What is a typical charge retention test?

Discharge the battery at 0.2C to 3.0V/cell, charge it at 1C in CC-CV mode to 4.2V, with a cut-off current of 10mA, then store it for 28 days at a temperature of 20±5 degrees Celsius, discharge at 0.2C to 2.75V, and calculate its discharge capacity. Compare it with the nominal capacity of the battery, it shall not be less than 85% of the initial capacity.

12. What is the internal pressure of a battery? How much is the normal internal pressure of a battery?

The internal pressure of a battery is the pressure formed by the gases generated during charging and discharging. It is mainly affected by battery materials, manufacturing processes, and other factors. In general, the internal pressure of a battery is maintained at a normal level, and, however, such pressure may rise under conditions of overcharge or over-discharge.

13. What is an internal pressure test?

The internal pressure test of a lithium battery is as follows (UL Standard):
Check whether the battery leaks or bulges in a simulated environment with an altitude of 15,240 m (low pressure of 11.6kPa).
Specific steps: charge the battery at 1C in CC-CV mode to 4.2V, with a cut-off current of 10mA, then store it in a box for six hours with an air pressure of 11.6Kpa and a temperature of 20±3 degrees Celsius, as a result, the battery shall not catch fire, explode, crack or leak.

14. What is a burning test?

Put the fully-charged battery in an explosion-proof container, then use a lead to link positive and negative electrodes to create a short circuit. As a result, the battery shall not catch fire or explode.

15. What is a drop test?

From three different directions, drop the fully-charged battery pack at a one-meter height onto a stiff rubber board, and do the drops twice in each direction. As a result, the battery pack should still function properly, and its package shall not break or crack.

16. What is a vibration test?

A lithium battery shall be subjected to the following vibration test:
Discharge the battery discharge at 0.2C to 3.0V, then charge it at 1C in CC-CV mode to 4.2V with a cut-off current of 10mA, and then leave it aside for 24 hours. After that, it is subjected to the vibration based on the following conditions:

• 0.8mm amplitude
• Vibrate the battery between 10HZ-55HZ, and increase or decrease the vibration rate by 1HZ per minute.
• The voltage of the battery should vary within ±0.02V, and its internal resistance should vary within 5m.

17. What is an impact test?

Discharge the battery to at 0.2C to 3.0V, then charge it at 1C in CC-CV mode to 4.2V at 20℃, with a cut-off current of 10mA. Fix it onto an impact test table, and then conduct the test under the following conditions:
The peak acceleration stays at 100m/s2, the pulse lasts for 16 ms, and the number of impacts reaches 100010.After the impact, Observe the battery with naked eyes to make sure that it does not develop any abnormal phenomena. Then discharge the battery at 1C in CC mode to 2.75V, and then repeat charging/discharging at 1C at 20℃, till the discharge capacity is not less than 85% of the initial capacity, but the number of cycles cannot be greater than 3.

18. What is an impact test?

After the battery is fully charged, place a 15.8mm diameter hard rod horizontally on the battery and drop a 20-pound object from a height of 610mm to crash the rod. As a result, the battery should not catch fire, explode or leak.

19. What is a penetration test?

Drive a nail with a diameter ranging from 2.5mm to 5mm into the center of a fully-charged battery, leave the nail in there, and the battery shall not catch fire or explode.

20. What is a high-temperature accelerated life test?

Since a typical charge retention test needs a long time, usually a high-temperature accelerated life test is introduced for Ni-MH batteries. Place a fully-charged battery in a 45℃ environment for 3 days (equivalent to 28 days at room temperature), and then put it in a room-temperature environment for one hour. After that, discharge it at 0.2C to 1.0V, which shall last over 3 hours.

21. What is a high-temperature and -humidity test?

Charge the battery at 1C in CC-CV mode to 4.2V, with a cut-off current of 10mA, then put it into a constant temperature and humidity chamber at 40℃ and relative humidity of 90%-95% for 48 hours. then take out the battery and put it aside for 2h at 20℃. Observe the appearance of the battery to make sure that it is normal, discharge it at 1C in CC-CV mode to 2.75V, and then repeat the charging/discharging cycle at 1C at 20℃, till the discharge capacity is not less than 85% of the initial capacity, but the number of cycles cannot be greater than 3.

22. What is a temperature rise test?

Place a fully-charged battery into an oven, increase the oven temperature at a rate of 5 per minute until it reaches 150℃, and keep the. temperature for 10 minutes. As a result, the battery shall not catch fire or explode.

23. What is a temperature cycling test?

A temperature cycling test includes 27 cycles, and each cycle is made up of the following steps:

1. Move a battery from room temperature to an environment with a temperature of 66±3℃ and humidity of 15±5%, and leave it there for one hour.
2. Move it to another environment with a temperature of 33±3℃ and humidity of 90%, and leave it there for one hour.
3. Put it in a new environment with a temperature of -40℃, and leave it there for one hour.
4. Leave the battery aside at 25℃ for 0.5 hours.

These four steps make up a cycle. After 27 cycles, the battery shall have no leakage, alkali substance, rust, or any other abnormal phenomena.

24. What is a temperature shock test?

This test needs two thermostats, one at 66℃, and the other at -40℃. Each cycle consists of the following steps: leave the battery in the thermostat at -40℃ for one hour, and then within five seconds transfer it to the other thermostat at 66℃. This test shall start from a low temperature, and end at a high one. The whole process shall cover 24 cycles. After exposure to such cycles, the battery shall not have any performance issues.

25. What is a burning test?

In an explosion-proof chamber, put a fully-charged battery on a blue flame for baking, and the battery safety valve shall be turned on after a certain period of time.

What certification do batteries need?

Since electronics, information & communication, and other products are becoming wireless and portable, all high-performance components for these products are also becoming light, thin, short, and small. Batteries have been applied widely as the best power supply device, but global battery recalls over the past years have sparked concerns about the safety of battery products in the international market; meanwhile, market watchdogs of all countries have scaled up the level of their regulation on battery products, posing a challenge upon domestic battery manufacturers in improving product quality.

Product coverage

• Primary common dry battery, alkaline zinc manganese battery, lithium manganese battery, zinc silver battery, zinc-air battery, lithium iodine battery, etc.
• Secondary nickel-based battery, nickel-cadmium battery, Ni-MH battery, etc.
• Cell phone battery, lithium-ion battery, lithium polymer battery, etc.
• Secondary batteries for various digital products, laptop batteries, digital camera batteries, camera batteries, all cylindrical batteries, wireless communication batteries, portable DVD batteries, CD and MP3 player batteries, and tablet PC batteries, etc.
• Lead-acid accumulator for car starting, fixed lead-acid accumulator, small valve-controlled sealed lead acid battery...
• Secondary batteries for powering cars, batteries for electric vehicles, batteries for electric-driven equipment, and batteries for hybrid vehicles, etc.

Service Items

• Transport safety testing
• International Certification
• Safety certification
• EMC testing
• Chemical testing
• Electrochemical testing

Battery Testing Items

• Environmental testing
• Low-pressure
• Temperature cycling
• Thermal abuse
• Electrical testing
• Rated capacity
• Discharge performance
• Over-discharge
• Overcharge
• Forced discharge
• High-rate charging
• External short circuit
• Endurance
• Charge retention and recovery
• Internal resistance
• Environmental testing
• Vibration
• Mechanical shock
• Free fall
• Crush
• Impact
• Electrostatic discharge
• EMC testing
• Electrochemical analysis
• Battery materials analysis

What are certification items of a battery?

General lithium battery certification is as follows:

• EU: CE, ROHS, 206/66/EC
• USA: FCC, UL, which is merely for the same model (different models require new certification), quite expensive
• Japan: PSE
• Korea: KC
• Taiwan: BSMI

In terms of safety, some customers may call for IEC62133, which is a safety compliance test.

As for transport, UN38.3 and MSDS tests are needed. These two are a must for either sea or air transport, especially when regulations on batteries are increasingly stringent.

Common certification items for batteries:

• Electric performance testing: rated capacity, discharge performance, over discharge, over charge, forced discharge, high-rate charging, external short circuit, endurance, charge retention and recovery, internal resistance.
• Mechanical properties testing: vibration, mechanical shock, free fall, crush, impact.
• Environmental performance testing: height imitation, thermal cycling, thermal abuse.
• Other tests: electrostatic discharge, battery compatibility, battery electrochemical analysis, battery material characteristics analysis.

(1) Electrical test/Testing Items/Charging status/ Battery condition/ Temperature/Evaluation & testing method/Standard

1. External short circuit/Fully charged/Freshly-produced batteries/60℃ room temperature/Short circuit two electrodes via a wire with a resistance less than 50mΩ for over six hours/No explosion or flame
2. Forced discharge/Fully charged/Freshly-produced batteries/Ordinary room temperature/Adopt manufacturer-recommended current to conduct forced discharge by 250% of the calculated capacity. * If safety or protection functions have been delivered during the testing process, you can put an end to the test. No explosion or flame
3. Continuous charge/Fully discharged/Freshly-produced batteries/Ordinary room temperature/Adopt manufacturer-recommended methods to charge the battery for 28 days at the prescribed voltage/No explosion, flame or cracks
4. Over discharge/Fully discharged/Freshly-produced batteries/Ordinary room temperature/Adopt manufacturer-recommended current to charge the battery to 250% of the calculated capacity. * If safety or protection functions have been delivered during the testing process, you can put an end to the test. No explosion or flame
5. Large current charge/Fully discharged/Freshly-produced batteries/Ordinary room temperature/Adopt the current triple the manufacturer-recommended value to charge the battery to over 100% of the calculated capacity/No explosion or flames

(2) Mechanical performance testing/Testing Items/Charging status/Battery condition/Temperature/Evaluation and Testing methods/Standard

1. Vibration/Fully charged or fully discharged/Freshly-produced batteries/Ordinary room temperature/ Vibrate the battery in XYZ directions for 90 to 100 minutes with an amplitude of 0.8mm, a frequency of 10HZ, and a rate of 1HZ/min. After the testing, charge the fully-discharged battery to the full capacity recommended by the manufacturer. No explosion, flames, or deformation
2. Acceleration/Fully charged or fully discharged/Freshly-produced battery/Ordinary room temperature/ Conduct acceleration in units of time from an initial value of 3ms to a peak value ranging from 125g to 175g, with an average acceleration of 75g (g is the unit of gravitational acceleration). Conduct vibration in XYZ directions perpendicular to one another. After the testing, charge the fully-discharged battery to the full capacity recommended by the manufacturer. No explosion, flames, or deformation
3. Drop test/Fully charged or fully discharged/Freshly-produced battery/Ordinary room temperature/Conduct 10 free falls from a height of 1.9m onto the cement floor. After the testing, charge the fully-discharged battery to the full capacity recommended by the manufacturer. No explosion or flames
4. Nail penetrating the battery/Fully charged/Freshly-produced battery/Ordinary room temperature/Use a 2.5 to 5.0mm diameter nail to penetrate the battery along its longitudinal axle and leave the nail inside for 6 hours. No explosion or flames
5. Crush/Fully charged/Freshly-produced battery/Ordinary room temperature/Sandwich the battery in between two flat iron plates with its longitudinal axle parallel to the plates, and then apply a load of 13kN upon the battery/No explosion or flames
6. Impact/Fully charged/Freshly-produced battery/Ordinary room temperature/Put a cylindrical rod with a diameter of 7.9 mm above the top of the battery, perpendicular to the longitudinal axle of the battery. Drop a weight equivalent to 9.1kg from a height of 61cm. No explosion or flames
7. 10m drop/Fully charged/Freshly-produced battery/Ordinary room temperature/Drop the battery randomly onto the cement floor from a height of 10m No explosion or flames

(3) Environmental performance testing/Testing Items/Charging status/Battery condition/Temperature/Evaluation and Testing methods/Standard

1. High-temperature storage/Fully charged/Freshly-produced battery
   (a) After 5 hours of storage in an oven at 100°C, put the battery at a 20℃ place for 24 hours
   (b) After 30 days of storage in an oven at 60°C, put the battery at a 20℃ place for 24 hours
   No explosion or flames

2. Thermal shock Fully charged Freshly-produced battery Conduct 10 cycles between -20℃ and 40℃ within 2 hours, and within 5 minutes move the battery from the -20℃ place to a 60℃ place No explosion, flames, damages, or deformation

3. Low pressure/Fully charged/Freshly-produced battery/Room temperature/Put the battery at a place with an absolute pressure equivalent to or less than 11.6kpa for six hours/No explosion or flames

4. Temperature rising Fully charged Freshly-produced battery Put the battery in an oven, and heat it to 130℃ at a rate of 5±2℃ per minute. And then put it in the oven for around 60 minutes No explosion or flames

5. Falling into the water/Fully charged/Freshly-produced battery/Room temperature/Immerse the battery in water for 24 hours/No explosion or flames