Specifications of a Lithium-Ion Cell
A lithium ion cell datasheet was chosen to answer the following:
https://www.ineltro.ch/media/downloads/SAAItem/45/45958/36e3e7f3-2049-4adb-a2a7-79c654d92915.pdf
1) What is the difference between nominal voltage and maximum voltage?
Nominal voltage - the voltage for which the circuit-breaker is designed to be used
Maximum voltage - voltage that the circuit-breaker can interrupt safely and without being damaged. Also referred to as rated voltage, which is within a certain range of the nominal voltage
2) Under which situation do we observe the changes in dimensions and weight of a cell?
Dimension - During cycles, the battery thickness changes for the three reasons — expansion and contraction of host materials due to lithium intercalation, electrode volume increase caused by irreversible reaction deposits, and dead volume and pressure changes within the cell case depending on battery structure and construction
Weight - there could be two possible scenarios here:
a. The battery reacts chemically with the environment (this is especially the case with Lithium-air batteries)
b. Some change in mass due to the energy equivalence theory of Einstein (E = mc2), which would deduce that when there is energy discharge, mass will reduce too. Although during charge and discharge the lithium ions and electrons are just moving from one electrode to the other, so overall mass should not be affected. However, due to Einstein's theory, when the capacity of the battery is 85kWh for instance, and the battery is fully discharged, according to the formula, that would reduce the mass by 3.41E-9 grams, which can be regarded as immeasurable and insignificant.
3) List out various mechanical testing and standards.
| Mechanical Test | Procedure | Requirement |
| Impact Test | A test sample battery is to be placed on a flat surface. A 5/8 inch (15.8mm) diameter bar is to be placed across the center of the sample. A 20 pound (9.1kg) weight is to be dropped from a height of 24 ±1 inch (610±25mm) onto the sample | No fire no explosion |
| Anti-vibration | The fully charged cell is fixed on a platform and vibrated in the X , Y and Z directions for 30minutes at the speed 10ct/min Frequency: 10~30Hz, Vibration amplitude 0.38mm. Frequency: 30~55Hz, Vibration amplitude 0.19mm. | No deformation should be visible. Not leak, smoke and/or explode. Voltage should be not less than 3.6V |
| Drop Test | The fully charged cell is dropped from a height of 1m onto a 15~20mm hard board in X, Y and Z directions once for all axis. Then the cell is discharged at 1.3A to 3.0V followed by 3 or more cycles with the standard charge rate and a discharge at 1.3A. | No fire, no explosion. Discharge Time≥102min |
| Standard conditions for test | All the tests need to be done within one month after the delivery date under the following conditions : Ambient Temperature:25±5℃; Relative Huimdity:65±20% | ||
| Standard Charge | Constant Current and Constant Voltage (CC/CV) Current = 0.52A Final charge voltage = 4.2V Final charge Current = 0.052A | ||
| Standard Discharge | Constant Current (CC) Current = 0.52A End Voltage = 3.0V | ||
4) What is the discard procedure suggested generally for used Li-ion batteries?
| Do | Don't |
|
- When the battery is thrown away, be sure it is non-conducting by applying vinyl tape to the (+) and - Ensure lithium batteries are not exposed to high temperature or prolonged sunlight - Handle these batteries carefully and package them so the safety device (casing) is not damaged. This can easily happen when batteries are stacked without a protective layer or placed beneath heavy objects |
- Do not expose batteries to water or humidity - Do not disassemble batteries. Crush, puncture, throw or do anything to the batteries that might result in electrodes touching and short-circuiting - Dispose of li-ion batteries with ‘regular’ waste. Disposing with regular flammable or plastic trash, they might ignite in a garbage truck or an incinerator, causing fire hazards - Mix damaged and non-damaged batteries - Place large numbers of batteries together without proper segregation, as this presents an increased fire hazard |