1. Lithium battery series parallel combination method

2-string lithium battery combination (7.4V lithium battery)

2. Lithium battery pack wires/terminals

The length of the lithium battery pack plug and lead can be customized according to the customer's electrical equipment.

1、

Series connection of lithium batteries with different voltages

Due to consistency issues, lithium batteries need to be paired in parallel within the same system (such as ternary or iron lithium), and it is also necessary to select those with consistent voltage, internal resistance, and capacity for grouping. Using batteries with different voltage platforms and internal resistances in series can cause a battery to be fully charged and discharged before each cycle. If there is a protective board and it does not malfunction, it will result in a decrease in the overall capacity of the group. Without a protective board, it will inevitably cause overcharging or overdischarging of the battery, leading to damage.

2、Parallel connection of lithium batteries with different capacities

If different capacities or old and new lithium batteries are mixed together for use, there may be phenomena such as leakage and zero voltage. This is due to the difference in capacity during the charging process, which causes some batteries to be overcharged while others are not fully charged. When discharging, some batteries with higher capacity are not fully discharged, while those with lower capacity are overdischarged. This vicious cycle results in battery damage leading to leakage or low (zero) voltage.

1、

Lithium battery series charging

At present, the charging of lithium battery packs generally adopts series charging, mainly because the series charging method has a simple structure, low cost, and is relatively easy to implement. However, due to the differences in capacity, internal resistance, attenuation characteristics, self discharge and other performance between individual lithium batteries, when charging a lithium battery pack in series, the smallest capacity individual lithium battery in the battery pack will be fully charged first, while other batteries have not yet been fully charged. If the series charging continues, the fully charged individual lithium battery may be overcharged.

However, overcharging lithium batteries can seriously damage their performance and may even cause explosions and personal injury. Therefore, in order to prevent overcharging of individual lithium batteries, lithium battery packs are generally equipped with a Battery Management System (BMS) during use, which provides protection for each individual lithium battery through overcharging and other measures. When charging in series, if the voltage of a single lithium battery reaches the overcharge protection voltage, the battery management system will cut off the entire series charging circuit and stop charging to prevent this single battery from being overcharged, which will cause other lithium batteries to be unable to fully charge.
2. Parallel charging of lithium batteries

When lithium batteries are charged in parallel, each lithium battery should ensure balanced charging, otherwise it will affect the performance and lifespan of the entire set of lithium batteries during use. The commonly used balanced charging techniques include constant shunt resistance balanced charging, on-off shunt resistance balanced charging, average battery voltage balanced charging, switched capacitor balanced charging, buck converter balanced charging, inductor balanced charging, etc.

Several issues need to be noted for parallel charging of lithium batteries:

Lithium batteries with and without protective plates cannot be charged in parallel. Batteries without protective plates are prone to overcharging and damage.

Parallel charging batteries usually require the removal of the battery's built-in protection board and the use of a single battery protection board.

If a battery charged in parallel does not have a lithium battery protection board, the charging voltage must be limited to 4.2V and a 5V charger cannot be used.

After parallel connection of lithium batteries, there will be a charging protection chip to provide charging protection for the lithium batteries. Lithium battery manufacturers have fully considered the changing characteristics of lithium batteries after parallel connection when making parallel lithium batteries, and have also designed the current and selected the battery cells according to the above requirements. Therefore, users need to follow the instructions of the parallel lithium battery to charge it step by step, in order to avoid possible damage to the battery caused by incorrect charging.
3. Precautions for charging lithium batteries

Lithium batteries must use dedicated chargers, otherwise they may not reach saturation and affect their performance.

Lithium batteries do not need to be fully discharged before charging.

Do not plug the charger into the socket for a long time. After the battery is fully charged, it should be removed from the charger as soon as possible.

The battery should be removed from electrical appliances that have not been used for a long time, emptied, and stored.

Do not plug the positive and negative terminals of the battery in reverse, otherwise it may cause the battery to swell or break.

Nickel chargers and lithium chargers cannot be mixed.