During charging and discharging cycles, battery cells face over current, over voltage, and over temperature conditions. The charging process for Lithium batteries consists of two phases: constant current and constant voltage. In the constant current charging phase, the charge current is applied to the battery until the voltage limit per cell is reached. Li-ion batteries cannot accept a higher voltage charge than specified, typically 4.2 V, without being damaged. The constant voltage phase then begins as the applied current declines to a few percent of the constant charge current.
During this time, the maximal cell voltage is applied to the battery. For multi-cell battery packs, a balancing phase occurs between the constant current and constant voltage phases to ensure a consistent charge among cells. In such packs, the voltage applied in the constant voltage stage is the product of the number of cells and the maximal voltage per cell.
LFP battery cells must never be discharged below their specified minimal voltage. Once voltage drops to this level, battery management system may stop the flow of current. This precaution ensures that the battery can be recharged safely with a conventional charger and protects the battery from a short circuit, which is a real threat to its integrity. If a short is sufficiently mild, little heat will be generated and the battery will simply discharge more rapidly. However, more severe shorts may result in overheating and its associated threats. In a multi-cell pack, the cells adjacent to the shorted cell can overheat or fail.
UL 2054 Tests and Requirements for Battery Packs
|
Electrical Tests
|
Requirements
|
|
Short circuit test
|
No explosion, no fire, temperature < 150 °C
|
|
Abnormal charging test
|
No explosion, no fire
|
|
Abusive overcharge test
|
No explosion, no fire
|
|
Forced discharge test
|
No explosion, no fire
|
|
Limited power source test
|
No explosion, no fire
|
|
Battery pack component temperature test
|
Temperature within specification
|
|
Battery pack surface temperature test
|
Temperature within specification
|
|
Environmental Tests Requirements
|
Requirements
|
|
Heating test
|
No explosion, no fire
|
|
Temperature cycling test
|
No explosion, no fire, no venting, no leaking
|
|
Mechanical Test Requirements
|
Requirements
|
|
Crush
|
No explosion, no ignite
|
|
Impact
|
No explosion, no ignite
|
|
Shock
|
No explosion, no fire, no venting, no leaking
|
|
Vibration
|
No explosion, no fire, no venting, no leaking
|
|
Battery Enclosure Tests Requirements
|
Requirements
|
|
250 lb. crush
|
No explosion, no fire
|
|
Mold stress relief
|
No explosion, no fire
|
|
Drop impact
|
No explosion, no fire
|
|
Fire Exposure Test Requirements
|
Requirements
|
|
Projectile
|
No explosion, no ignite
|
In order to ensure that LFP batteries can power electronics safely and meet regulatory requirements, several precautions need to be taken. Layers of protection include the construction method, density of the cell and safety mechanisms integrated within the cell. Electronics are then used outside the cell in order to protect from overcharge, undercharge, and extraneous temperatures. Circuit protection solutions of the BMS for battery packs are typically a combination of several devices, which are crucial design considerations during charging and discharging of the battery pack.
Battery management systems Integrated Circuits (ICs) and FETs (Field-Effect Transistors) provide overvoltage and over current protection. Integrating high tech protective devices is an optimal over temperature protection solution for battery packs and battery cells. In order to provide reliable protection, EverExceed BMS includes the protective device which is mounted in such a way that it is linked thermally with the cell. Typically, the protective device of the BMS will be in contact with the battery cell, so it can react to the increased temperature in the cell.
In order to meet the growing needs for battery cell and battery pack design,
EverExceed continues to innovate and expand its technical capabilities. EverExceed have been a leader in the
battery industry for decades and it offers a broad portfolio and provides designers with batteries perfect protection components to meet the needs of increasingly complex, demanding, and compact battery packs. With excellent customer service and the availability of field application engineers, EverExceed work closely with designers to choose the appropriate components, with modifications as necessary. It also offers excellent battery chargers like “
EverExceed Smart Charger” to provide full protection to the battery operation beside its reliable
BMS.
During a cell production process, EverExceed individually tests each cell in several phases, like 72hrs HT aging, 3 OCV tests, 14 days RT aging, capacity test, Over-charge, Over-discharge, Short circuit test, extrusion test, prick test, combustion test, salt spray corrosion test etc. After passing through all these tests, it is impossible for a battery to pass through the gate of our factory with any kind of fault that can cause any hazards later.
So for not only having the long cycle life, uninterrupted discharging performance, fast charging capability, higher energy density, but also if you need a lithium battery which will give you worry free operation, and less stress regarding the safety,
EverExceed Lithium iron phosphate batteries are the best choice for you, because EverExceed LFP guarantees you NO FIRE, NO EXPLOSION!
