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Sep 24,2020

# Comparison of battery series and parallel

### The method of battery series connection:

The positive electrode of the latter battery is connected to the negative electrode of the previous battery, and only the positive electrode of the first battery and the negative electrode of the last battery is left. The battery has two terminals, the positive terminal marked with +, and the negative terminal marked with -. Multiple battery connection methods are divided into series and parallel.

The series connection of storage batteries requires high-power portable equipment, which is generally powered by a battery pack with two or more batteries connected in series. If a high-voltage battery is used, the size of the conductor and switch can be made small.

After batteries with the same parameters are connected in series, the output current remains unchanged, and the output voltage is the sum of the output voltages of each battery. For example, if four 12V10A batteries are connected in series, the output voltage is 48V, and the output current is still 10A.

Batteries with the same parameters are connected in parallel to connect the positive and negative poles of all batteries respectively. After the parallel connection, the output voltage remains unchanged, and the output current is the sum of the output current of each battery.

Another problem brought by the use of high-voltage battery packs is that one of the batteries in the battery pack may fail. This is like a chain, the more batteries connected in series, the higher the chance of this happening. As long as a battery has a problem, its voltage will drop. In the end, a "disconnected" battery may interrupt the current delivery. And to replace the "bad" battery is not easy, because the old and new batteries do not match each other.

### The method of parallel connection of batteries：

To get more power, you can connect two or more batteries in parallel. In addition to connecting the batteries in parallel, another solution is to use larger batteries. Due to the limitation of the available batteries, this method is not suitable for all situations.

In addition, large-sized batteries are not suitable for the external specifications required for special batteries.

Most chemical batteries can be used in parallel, and lithium-ion batteries are most suitable for parallel use(ultra thin lithium polymer battery). In a battery pack formed by connecting four batteries in parallel, the voltage remains at 1.2V, while the current and running time is increased to four times.

Examples of battery packs Compared with batteries in series, in battery parallel circuits, high impedance or "open circuit" batteries have less impact, but parallel battery packs will reduce the load capacity and shorten the running time.

The voltage of a series battery is the sum of the voltages of each sub-battery, and the output power (that is, the power after series connection) is related to the weakest capacity of a single battery.

The voltage of the parallel battery is the maximum voltage of each sub-battery, and the output power is N times the weakest sub-battery of the battery pack (N is the number of sub-batteries).

Because the output power of battery packs in series or in parallel is related to the weakest battery in the battery pack, it is required to select sub-cells with the same degree of new and old and nearly the same performance in the battery pack, otherwise, the performance of the battery pack is good ( (Or new) sub-batteries have to work on the weak sub-batteries, thereby reducing the efficiency of the entire battery pack, and also detrimental to the life of the best sub-batteries.