Lithium ion battery charging requirements, how does the charger determine whether the lithium ion battery is fully charged? The charger determines whether the charging is complete by detecting the charging current and voltage, and together with the overcharging protection of the phone, ensures that the lithium-ion battery of the phone will not overcharge. Poor quality chargers do not have this detection process, and although there will be no problems in the short term, overcharging over time or several times can affect the lifespan of lithium-ion batteries.
Generally, lithium-ion batteries have a chip inside, which automatically cuts off the charging current when fully charged to protect the battery from being damaged. In this state, only a small amount of current is still charging the battery.
Charging requirements for lithium-ion batteries
① The basic requirements for charging lithium-ion batteries are specific charging voltages and currents at each stage, and some additional auxiliary functions are added to improve the battery's lifespan;
② To ensure the stable and reliable operation of the battery and prevent interference from transient voltage changes, a delay circuit with overcharging, discharging, and overcurrent protection should be designed internally to prevent instability caused by transient interference;
③ The factors that affect the safety and effective charging of lithium-ion batteries include voltage, current, and temperature. Therefore, in the design of chargers, these three factors should be taken into consideration and controlled;
④ The lithium-ion battery charger has a simple circuit, fewer peripheral components, and takes up less space. It can generally be made in batteries or battery packs;
⑤ To partially discharge lithium-ion batteries and prevent frequent complete discharge; Overdischarge may have catastrophic consequences for the battery, or repeated discharge may have a particularly significant impact on the battery.
How can a charger determine whether a lithium-ion battery is fully charged?
Firstly, it is necessary to ensure that the charger matches the electrical appliance to be charged. Voltage matching and current matching are very important, and the current index of the charger determines the charging time. The higher the current index, the faster the charging speed; The second common judgment is the color change of the indicator light on the charger or the light on the appliance, which generally changes from red to green to indicate full charge.
When measuring the voltage of an electrical appliance, the terminal voltage of the battery varies depending on the battery level. The lower the battery level, the lower the voltage. Therefore, the voltage of the battery has a range from the lower limit that can ensure the normal operation of the appliance to full charge.
Lithium ion batteries can be directly judged based on the battery voltage. When the voltage exceeds the set cutoff voltage, the battery is considered fully charged; Advanced chargers use a combination of voltage and current for judgment. When the voltage approaches the cut-off voltage, it switches to constant voltage charging. When the current is less than a certain set value, it is considered that the battery is fully charged.
A regular charger that uses the lowest level voltage comparison method can quickly determine a "fully charged" battery, because voltage comparison chargers only determine the battery voltage. As long as the voltage of the battery reaches, it is judged as "fully charged", and usually there is still a lot of room for the battery to reach saturation at the voltage, which is basically not fully charged. So this judgment method is generally only used on the lowest level chargers.
The charger should be unplugged when it indicates full charge. Nowadays, chargers generally have a fully charged and self stopping design, so it's okay not to remove the lithium-ion battery from the charger for a short time. However, if the battery is left on the charger for a long time, and the power grid voltage rises late at night, chargers that have already stopped charging will continue to overcharge the lithium-ion battery, which will affect its lifespan.