Does The Lithium-Ion Battery Depend On The Calendar Life Or The Cycle Life?
For how long a battery can be used is related to the cycle life and the calendar life of the battery.The cycle life is the number of times the lithium-ion battery can be charged and discharged. The calendar life is the battery to reach the end of life condition (capacity decays to 80%)under specific operating conditions and the environmental conditions.
Factors for affecting cycle life
Partial discharge:Using only 20 or 30 percent of the battery capacity before charging will greatly extend the cycle life.Generally speaking, one full discharge cycle is equal to 5 to 10 shallow discharge cycles. Although thousands of times partial discharge cycles can be occurred , keeping the battery fully charged also shortens its life. If possible full discharge cycles should avoid as much as possible (down to 2.5 or 3 volts, depending on the chemical composition).
- Avoiding charging to 100% capacity:For this,you can choose a lower floating voltage.Lowering float voltage increases cycle life, but at the expense of reducing battery capacity.Reducing the float voltage from 100-mV to 300-mV can extend the cycle life by 2-5 times or more.Compared with other chemical reagents, lithium ion cobalt reagents are more sensitive to higher floating pressure.Lithium-ion phosphate batteries usually have a lower float voltage than conventional lithium-ion batteries.
- Selecting the correct charge termination method: Choosing a minimum charging current terminal charger (C/10 or C/x) can also extend battery life by not charging to 100% capacity.For example, when the current drops to C/5, ending a charging cycle, this is similar to reducing the float voltage to 4.1V. In both cases, the battery is only charged at about 85 percent of capacity, which is an important factor in battery life.
- Limiting battery temperature: Limiting the temperature of lithium-ion batteries can extend their service life, especially at temperatures below 0℃.When charging below 0℃, it will promote the metal coating of battery anode, form internal short circuit and generate heat, making the battery unstable and unsafe.Some battery chargers measure battery temperatures to ensure that charging does not occur at extreme temperatures.
- Avoiding high charge and discharge currents: The cycle life will reduced when charge or discharge currents are too high . Some chemistries like Li-ion manganese and Li-ion phosphate are more suited for higher currents. High currents will put excessive pressure on the battery.
- Avoiding extremely deep discharges (below 2 V or 2.5 V): Extremely deep discharges will damage a lithium-ion battery quickly and permanently. This will cause a short circuit of internal metal plating,and will make the battery unusable and unsafe. Most lithium-ion batteries have protection circuitry within their battery packs,which open the battery connection if the battery voltage is less than 2.5 V or exceeds 4.3 V, or if the battery current exceeds a predefined threshold level when charging or discharging.
Factors for affecting the calendar life
- Aging of battery: The calendar aging of the battery is mainly due to the formation of a passivation layer on the negative electrode. The formation of films on positive and negative electrodes is mainly a process of aging. The calendar life of a battery is affected by the charged state (SOC) it stores. The effect of SOC on calendar life will depend on battery chemistry. Lead-acid batteries need to be stored at full charge for maximum life, while lithium-ion and AGM deep-cycle batteries need to be stored at 40 per cent full charge.
- Storage temperature:The temperature at which the battery is stored also affects the calendar life. As the temperature rises, the rate of reaction speeds up.This increases the rate of unnecessary chemical reactions and also increases battery degradation.High temperatures are detrimental to the battery’s calendar life.
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