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Charging or discharge rates are typically represented according to battery capacity. This speed is called C rate. The C rate is equal to the charging or discharge current under certain conditions, defined as follows: i = m×CN where: i = charging or discharge current, am = C multiples or fraction c = nominal capacity value, AHN = hour number (corresponding to C).
The battery discharged in a 1x C rate will release the rated capacity of the standard within an hour. For example, if the nominal capacity is 1000 mAhr, then the discharge rate of 1C corresponds to the discharge current of 1000 mA, and the rate of C / 10 corresponds to a discharge current of 100 mA. Usually the battery capacity of the manufacturer is N = 5, that is, 5 hours of discharge capacity.
For example, the above battery can provide 5 hours of working time when 200 mA constant current discharge. In theory, the battery can provide 1 hour working hours when the battery is discharged at 1000mA. However, actually due to the decrease in performance during the discharge of the large battery, the working time at this time will be less than 1 hour.
So how can I correctly charge a lithium-ion battery? The most suitable charging process of lithium-ion batteries can be divided into four phases: trickle charging, constant current charging, constant voltage charging and charging termination. Stage 1: Trickle charging - trickle charging is used to prechart the completely discharged battery unit (recovery charging). When the battery voltage is less than 3V, charging the battery first using a constant current of the maximum 0.
1c. Stage 2: Constant current charging - When the battery voltage rises to the trickle charging threshold, improve the charging current for constant current charging. Constant current charging current between 0.
2c to 1.0c. The current at constant current charging does not require it very accurate, and the regular constant current can also.
In linear charger design, current often increases with the rise of the battery voltage to minimize heat dissipation problems on the transmission transistor. The constant current charging greater than 1C does not shorten the entire charging cycle time, so this practice is not available. When charging at a higher current, the battery voltage will rise faster due to the overvoltage of the electrode reaction and the voltage on the internal impedance of the battery.
The constant current charging phase will be shortened, but due to the following constant pressure charging phase, the total charge cycle time will not be shortened. Phase 3: Constant voltage charging - When the battery voltage rises to 4.2V, the constant current charging ends and starts the constant voltage charging stage.
In order to achieve the best performance, the regulator tolerance should be better than + 1%. Stage 4: Charging Termination - Unlike the nickel battery, it is not recommended to continuously charge the lithium ion battery. Continuous trickle charging can cause metal lithium electroplating effect.
This will make the battery unstable and may result in sudden automatic fast disintegration. There are two typical charging termination methods: the minimum charging current is used to determine or use the timer (or the combination of both). The minimum current method monitors the charging current in the constant pressure charging stage, and terminates charging at the rate of charge current decreases to 0.
02c to 0.07c. The second method begins at the beginning of the constant voltage charging phase, and the charging process is terminated after two hours of charging.
The above four-stage charging method completes the charging of the full discharge battery for 2.5 to 3 hours. Advanced chargers also use more security measures.
For example, if the battery temperature exceeds the specified window (usually 0 ¡ã C to 45 ¡ã C), then charging will be suspende.
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