Lithium polymer batteries have the characteristics of low memory effect, low self-discharge characteristics, light weight, high capacity, and high voltage. They are very suitable for use in aviation models and electric models that require lightweight, which has solved the problem of excessive battery weight and insufficient discharge capacity for many years.
Polymer batteries are favored by all walks of life for their advantages of fast charge and discharge, large capacity, etc., and now they have become the choice of special lithium batteries in many industries.However, for users, the correct use and charging of polymer batteries is very important, otherwise it will affect their life and increase costs.So, how to use it correctly? Let’s know the method to charge Li-Po battery first.
How to Charge Li-PO Battery?—-Charging Method
Main Contents
The charging method of lithium poly batteries adopts the method of constant voltage and variable current. Because the voltage requirements are quite precise, it is important to use a dedicated lithium battery balanced charger.The quality of the charger will affect the charging accuracy, thereby affecting the service life of the battery.
- Constant current charging—–CC-Charging
According to the size of the charging current, constant current charging can be divided into fast charging, standard charging and trickle charging.During the entire charging process, it is generally used to adjust the charging voltage of the power supply or change the resistance value in series with the battery to keep the charging current of the battery unchanged.The advantage of this method is that it is simple to control and is suitable for charging battery packs with multiple batteries in series.The disadvantage is that the acceptable charging capacity of the lithium battery will gradually decrease as the charging progresses. Excessive charging current in the late stage of charging will cause air bubbles inside the battery and cause damage to the battery.Therefore, constant current charging is often used as a link in the stage charging.
- Constant voltage charging—-CV-Charging
Constant voltage charging means that the charging voltage remains constant throughout the charging process, and the size of the charging current is automatically adjusted as the battery state changes.As the charging progresses, the charging current gradually decreases.Compared with constant current charging, the charging process is closer to the optimal charging curve, with simple control and low cost.The disadvantage is that the charging time is long, and the battery charging current is too large in the early stage of charging, which directly affects the life and quality of the lithium battery.Therefore, the constant voltage charging method is rarely used alone, and only when the charging power supply voltage is low and the current is high.
- Constant current and constant voltage charging—-CC-CV-Charging
Figure 2 shows the constant current and constant voltage charging curve.Before starting charging, the battery voltage is first detected. If the battery voltage is lower than the threshold voltage (about 2.5V), the battery is recharged with a small current of C/10, so that the battery voltage rises slowly; when the battery voltage reaches the threshold voltage, it enters constant current charging. At this stage, the battery is quickly charged with a larger current (0.5C~1 C) intensity, the battery voltage rises faster, and the battery capacity will reach about 85% of its rated value; after the battery voltage rises to the upper limit voltage (4.2V), the circuit switches to a constant voltage charging mode, and the battery voltage Basically maintained at 4.2V, the charging current gradually decreases and the charging speed slows down. This stage is mainly to ensure that the battery is fully charged. When the charging current drops to 0.1C or 0.05C, it is determined that the battery is fully charged.
- Intermittent charging method
The intermittent charging method of lithium batteries includes the intermittent charging method of variable current and the intermittent charging method of variable voltage
Charger Classification
Chargers are classified according to battery type. Common chargers are: lead-acid battery chargers, lithium iron phosphate chargers, ternary lithium battery chargers, nickel-metal hydride battery chargers, nickel-cadmium battery chargers, etc. So there is another problem:
How to Select the Right Li-Po Battery Charger?
As far as the current research report shows, most lithium battery accidents are caused by chargers.Therefore, the choice of lithium battery charger is very critical, so how to choose the right lithium battery charger? We will you some suggestions as follows：
1.Voltage Adaptation Principle
The size of the charger voltage also varies with the number of battery strings；
To take Selecting Li-Po battery Charger as an example：
Charger voltage for 60V16 series of ternary lithium batteries: 4.2V16 series=67.2V; charger voltage for 60V19 series of lithium iron phosphate batteries: 3.65V19 series=69.35V, the charger voltage shown below is 60—73V, which can be used to charge 60V lithium iron phosphate batteries.
Take the Selecting LiFePO4 battery charger as an example：
——If your lithium battery voltage is 48V, you cannot choose a lithium battery charger with an input voltage larger than 54.75V, nor can you choose other types of battery chargers with an input voltage smaller than 54.75V. You can only choose a lithium battery charger with an input voltage of 54.75V.
——If your lithium battery voltage is 60V, you can only choose a lithium iron phosphate battery charger with an input voltage of 69.35V. You cannot choose a charger with an input voltage of less than or greater than 69.35V, let alone a charger for other types of batteries.
——If your lithium battery voltage is 72V, you can only choose a lithium iron phosphate battery charger with an input voltage of 83.95V. You cannot choose a charger with an input voltage of less than 83.95V.
2.Current Adaptation Principle
The current of the charger should be adapted to the lithium battery. Don’t covet fast charging. Use a high-current charger to charge a small-current battery, because a high-current charger will cause the internal resistance of the battery to increase and damage the protection board, thereby reducing the service life of the lithium battery. The current of the charger should be adapted to the lithium battery. Don’t
3.Charging Interface Adaptation Principle
Common lithium battery charging interfaces are Pin header interface, three horizontal interface, three vertical interface, round head interface, Giant interface, and two-plug plug. The most commonly used lithium battery plug for electric vehicles is the three-vertical interface.
In addition to the above tips, we must also have an understanding of our own electric vehicle batteries. Consult a professional before buying a charger, rather than just buying a charger to charge the battery. In the end, the battery damage caused by the charger problem is very much not worth the loss.
Precautions for the Usage of Li-Po Battery Chargers
PART.01
It is best to charge the Li-Po battery according to the method in the specification.If there is no specification, then you need to check the capacity of the Li-Po battery and the current of the charger.For example, for a 48V/20A lithium battery, if the charger is 5A, it will take a little more than 4 hours to charge. If it is a 10A charger, it will take a little more than two hours, and a 20A charger will take an hour to charge.
PART.02
Generally, the Li-Po battery in newly purchased equipment is new, so the battery capacity is also large, so the charging time will be longer.Take a 48V/40Ah Li-Po battery and a 5A charger as an example. The charging time will reach more than 10 hours at the beginning.With the increase of the number of recharges, the charging time will be shortened. It will be reduced to 8 hours after about 2 months. After that, it will be constant and last for about half a year. The battery capacity will continue to decay, and it will be fully charged in 6.5~7.5 hours after 1 year.Of course, if the battery can complete a charge and discharge cycle every day, then careful maintenance is required at this time to extend the service life as much as possible.
PART.03
After purchasing equipment with Li-Po batteries, lopo batteries generally have about 80% of the power.So you should charge the battery as soon as you get home.The time is based on 1~2 hours after the charger turns on and then recharges. It is best to perform this operation three times.
PART.04
The Li-Po battery should not be charged for too long, one hour after the charger turns on the light is appropriate.The charging time is better to charge less than to overcharge, otherwise the Li-Po battery will bulge and swell due to overcharge, resulting in irreparable losses to the Li-Po battery.
PART.05
The discharge port and charging port of Li-Po batteries should be kept clean at all times to prevent patina from appearing at the contact points, causing poor contact and overheating and damage.
PART.06
Before charging for the first time, the Li-Po battery will run out of power, but it cannot be used up.When the electric bicycle is newly bought, the battery will not be too full, but it will not be too little, unless it is an old battery or an inferior battery.When you are using it, you should estimate the approximate working time based on the data of the merchant so as not to run out of battery power.
PART.07
Li-Po batteries do not need to be activated, because Li-Po batteries are a type of lithium battery. Lithium batteries have no memory effect, and the battery will activate naturally during battery use.
PART.08
A regular deep discharge is also conducive to “activating” the battery, which can slightly increase the capacity of the battery.The general method is to perform a complete discharge of the battery on a regular basis.
