T.1 Altitude Simulation
Common sense tells us that the higher altitude, the lower pressure. When an airplane takes off from the ground to its cruising altitude of 30,000 feet, the air pressure inside the plane slowly decreases as the altitude increases. When the plane lands, the air pressure inside the cabin increases gradually as the altitude decreases.
Although the aircraft shall pressurize and depressurize the cabin during ascent and descent, there is always a pressure difference that can’t be avoided. If a cargo plane carries lithium cells/batteries, or products with lithium batteries, how do we determine in advance whether the batteries inside the plane can withstand the pressure changes?
Thus, a chamber to simulate this type of high altitude with a low-pressure environment was born, its principle is very simple: in a sealed chamber, use the artificial method to generate a specified low-pressure environment, and put the lithium battery or lithium cell in the test chamber, after a specified time, then take out the battery or cell to evaluate whether it meets the standard.
T.2 Thermal Test
At the same time, the temperature of the world is very different between different countries and regions. If a battery is transported from low latitudes to high latitudes, the battery will experience a temperature difference from high to low temperature. Conversely, If transported from high latitudes to low latitudes, the battery will experiences a temperature difference from low to high temperature.
Not only that, If transported by cargo aircraft, the temperature is lower when it flies at a high altitude than that on the ground, and the temperature is also higher than that at high altitude when it lands. If shipped by sea, containers stuffed with lithium batteries/cells stack on the deck, also will experience a significant temperature difference between day and night while sailing on the water.
In short, batteries transported remotely must be subjected to extreme temperature variations.
The purpose of the thermal test is to use rapid and extreme temperature changes to evaluate lithium cell and battery seal integrity and internal electrical connections.
This test simulates vibration during transport. Not only the battery, for any transportation of goods, the vibration is difficult to avoid because any object displacement represents the occurrence of movement, accompanied by vibration.
In the process of handling, loading, transportation and unloading, vibration is unavoidable.
Take the example for air transport, barring turbulence in the air, the cargo hold vibrates continuously at a fixed frequency, even if the aircraft is usually cruising. This kind of vibration may not be felt by human perception, so it is directly ignored for common goods, but for such dangerous and sensitive goods like batteries, we should pay considerable attention to it in case of catching fire.
We need to simulate this similar environment ahead of time to see If the battery can maintain stable physical and chemical properties in such a vibration conditions and do not have other abnormalities.
When we usually take a passenger plane, the flight often appears up and down, left and right sway and fuselage vibration suddenly. This phenomenon is caused by atmospheric turbulence.
The reason why the airplane is bumpy is that there is turbulence in the atmosphere, varying in size, direction and speed.
When an aircraft enters a turbulence vortex similar to the size of the body, each part of the aircraft will be affected by airflow in different directions and speeds, and the original balance of aerodynamic force and torque will be destroyed, thus producing irregular movement. When an airplane moves from one vortex to another, it vibrates. When the aircraft’s natural vibration period is same as the turbulence pulsation period, the turbulence becomes very intense.
Once we understand the reason behind this phenomenon, you must know the necessity for a shock test for the batteries that will be airlifted.
Think about it, If the batteries which can’t withstand these shocks collide in the cabin due to turbulence at the height of 10,000 meters to cause a fire, which will be very terrible and disastrous.
T.5 External Short Circuit
This test simulates an external short circuit. Battery short circuit is a common fault of batteries, including external short circuit and internal short circuit.
The External short circuit generally refers to the short circuit caused by direct contact between positive and negative poles. No matter whether by sea, by air or by truck, external short circuit may occur in case of abnormal packaging, accidental changes in the external environment, or improper human handling.
When the battery short circuit occurs, the battery will continue to release heat, and the temperature is very high enough to melt the general metal. If there is no timely heat dissipation, It will burn out the battery, and cause fire or even explosion, becoming a serious threat to property and life safety.
We do this external short circuit test to know whether the battery is in controlled condition once the external short circuit happens.
These tests simulate mechanical abuse from an impact or crush that may result in an internal short circuit. Internal short circuit refers to the short circuit in the region of the battery affected by external objects when the battery is punctured by a sharp object or is collided or squeezed.
The primary purpose of this test is to test the internal stability and safety of the cell to prevent the battery from disintegrating or catching fire in the process of the sea, truck or air transportation due to externally uncontrollable factors, such as impact, dumping, collapse and so on.
These tests are only applicable to lithium cells less than 18mm in diameter.
This test assesses the performance of a rechargeable battery or a single cell rechargeable battery to resist an overcharge condition.
The battery is charged using a charge current and a charge voltage that exceeds the battery manufacturer’s specified values to know whether the specimen can meet the requirements of no disassembly and fire.
T.8 Forced Discharge
This test evaluates the ability of a primary or a rechargeable cell to withstand a forced discharge condition. Connect each cell in series with a 12V DC power supply at an initial current equal to the maximum discharge current specified by the manufacturer.