About the self-discharge of portable power station’s lithium batteries
The consistency of the self-discharge is one of the important part of the effect factor,the SOC of battery with inconsistency self-discharge will have a biggish difference after a period of storage and its capacity and security will be greatly affected. It help us to improve the overall level of our battery pack,get longer life and lower the fraction defective of the products through our studying.
When we put a battery or a lithium power station which containing a certain amount of electricity at a certain temperature and keep that way of a while,it will lose some of its capacity. To make a long story short, self-discharge is a phenomenon that the battery lose by the subsidiary reaction.
The Importance of Self-discharge
Currently, lithium battery are used more and more widely in laptop,digital camera and other digital devices, besides, it also have board prospects in vehicle,mobile base station, portable solar power station and some solar power system.Under these circumstances,battery is not only show up alone like in just a cell phone but also will show up in series or in parallel.
The capacity and life span of the battery pack is not just only related to every single battery, but also more related to the consistency between every single battery.Poor consistency can greatly drag the manifestation of the battery pack.
The consistency of the self-discharge is one of the important part of the effect factor,the SOC of battery with inconsistency self-discharge will have a biggish difference after a period of storage and its capacity and security will be greatly affected. It help us to improve the overall level of our battery pack,get longer life and lower the fraction defective of the products through our studying.
The Influence of Self-discharge
1.Self-discharge leads to the decrease of storage capacity.
Here are some typical problems caused by excessive self-discharge:
Such as Vehicle park too long and can’t start or portable power station outdoor storage too long then can’t use.
The battery voltage and other parameters were as usual but the voltage wqas found lower or even down to zero when the battery is delivered.
2.Self-discharge of the metal impurity type caused the blocking of diaphragm pore diameter, even piercing the diaphragm and bring about local short circuit,endangering the battery safety.
3.Self-discharge leads to the increase of SOC difference between batteries and make decrease of the battery pack capacity.
4.Because of the inconsistency of self-discharge, the SOC of the batteries in the battery pack is different after storage ,and the battery function decreases.Clients can often find the problem of performance degradation after getting the battery pack that has been stored for a period of time. When the SOC difference reaches about 20%,the capacity of the combined battery only left 60%~70%.
Self-discharge test
1..Self-discharge detection method
Voltage drop method
The rate of voltage decrease during storage is used to characterize the self-discharge.This method is easy to work but the disadvantage of method is that the voltage drop can not reflect the loss of capacity directly.Voltage drop method is the most simple and practical method, which is widely used in current production.
Capacity attenuation method
That is, the percentage of capacity reduction per unit time.
Self-discharge current method
According to the relationship between capacity loss and time, the self-discharge current ISD of the battery during storage is calculated.
Calculation of Li + mole number for side reaction consumption
Based on the influence of the electronic conductivity of the negative SEI film on the Li + consumption rate during storage, the relationship between Li + consumption and storage time was deduced.
Important point: BRIDNA lithium portable power station use A+grade Auto lithium battery,That self-discharge current of battery pack is lower than 26uA, but in order to extend the life cycle of your portable power station, we suggest you charge and discharge one time at least per 3 months to improve the battery efficiency.
