High voltage battery charging
According to the upper limit of charging voltage, polymer lithium batteries can be divided into high-voltage lithium batteries (4.35V/4.4V) and conventional lithium batteries (4.2V). The nominal voltage of conventional voltage batteries is 3.6/3.7V, the upper limit of charging voltage is 4.2V, the nominal voltage of high-voltage lithium batteries is 3.8V and 3.85V, and the corresponding charging cut-off voltages are 4.35V and 4.4V respectively. High voltage lithium batteries have only been widely used in the market in recent years, and they are also the commanding heights of the technical competition of high-voltage battery manufacturers. But how to charge the high-voltage lithium batteries is better. I believe many people still have this question. Today, Graeme Technologies will explain how to better charge the high-voltage lithium batteries?
Charging mode of high-voltage lithium battery
- Ordinary series charging
At present, lithium ion battery packs are generally charged in series, mainly because the series charging mode is simple in structure, low in cost and relatively easy to realize. However, due to the differences in the capacity, internal resistance, attenuation characteristics, self discharge and other performance of single lithium ion batteries, when the lithium ion battery pack is charged in series, the single lithium ion battery with the smallest capacity in the battery pack will be fully charged first, while other batteries are not fully charged. If the series charging is continued, the fully charged single lithium-ion battery may be overcharged.
Overcharging of lithium-ion battery will seriously damage the battery performance, and may even cause explosion and personal injury. Therefore, in order to prevent overcharging of a single lithium-ion battery, the lithium-ion battery pack is generally equipped with a battery management system. Each single lithium ion battery is charged and protected by the battery management system. During series charging, if the voltage of a single lithium-ion battery reaches the overcharge protection voltage, the battery management system will cut off the entire series charging circuit and stop charging to prevent a single battery from being overcharged, which will cause other lithium-ion batteries to fail to fully charge.
- The battery management system shall coordinate with the charger for series charging
The battery management system is the most comprehensive equipment to understand the battery performance and status. Therefore, establishing the connection between the battery management system and the charger can enable the charger to know the battery information in real time, so as to solve some problems during battery charging more effectively.
The charging mode principle of the coordination between the battery management system and the charger is: the battery management system monitors the current status of the battery (such as temperature, single battery voltage, battery operating current, consistency and temperature), and uses these parameters to estimate the maximum allowable charging current of the current battery; During the charging process, the battery management system is connected with the charger through the communication interface to realize data sharing.