Series Connection Method of Lithium Ion Cell Pack

It sounds simple to use power lithium ion cell in series and parallel. However, following some simple rules can prevent unnecessary problems. The lithium ion cell series consists of two parts including lithium ion cell and lithium ion cell protection board circuit.

1.Series connection of lithium ion cell battery

In the lithium ion cell series, multiple lithium ion batteries are connected in series to obtain the desired operating voltage. If you want higher capacity and higher current, you should connect lithium ion batteries in parallel. There are also some battery series that combine the two methods of series and parallel.

The battery of a laptop computer may be connected in series with four 3.6V lithium ion batteries, the total voltage reaches 14.4V. Then, two groups of batteries connected in series are connected in parallel. In this way, the total power of the battery series can be increased from 2000 mAh to 4000 mAh. This kind of connection is called four series and two parallel, which means that two groups of battery series composed of four batteries connected in series are connected in parallel.

The nominal voltage of a lithium ion cell is 3.6V. Using lithium ion polymer and other types of lithium ion batteries, its rated voltage is generally 3.7V. If you want to get an unusual voltage like 11.1V, you have to connect three such batteries in series. High-voltage portable devices are generally powered by a battery series with two or more batteries connected in series. Another problem brought by the use of high-voltage battery series is that one of the batteries in the battery series may fail.

This is like a chain, the more batteries connected in series, the higher the chance of this happening. As long as there is a problem with a battery, its voltage will drop. In the end, a disconnected battery may interrupt the flow of current. It is not easy to replace a bad battery, because the old and new batteries do not match each other. Generally speaking, the capacity of new batteries is much higher than that of old batteries.

2.Performances of lithium ion cell battery series

As the working voltage drops, the battery in question reaches the critical point of the end of discharge faster than the normal battery series, and at the same time, its use time is also drastically shortened. Once the device cuts off the power supply due to low voltage, the remaining battery cells are still intact and cannot send out the stored power.

At this time, the bad battery still presents a large internal resistance. If there is a load at this time, it will cause the output voltage of the entire battery chain to drop significantly.

In a series of batteries, a battery with poor performance is like a plug blocking a water pipe, and there will be huge resistance to prevent current from flowing or to disconnect the current loop of the battery series and cut off the current. The performance of a lithium ion cell series depends on the performance of the worst battery in the battery series.