How to correctly connect batteries in series and parallel

How to properly connect batteries in series and parallel may sound simple, but following a few simple rules can avoid unnecessary problems.

In a battery pack, multiple cells are connected in series to get the required operating voltage. If higher capacity and higher current are required, the batteries should be connected in parallel. There are also battery packs that combine the two methods of series and parallel. A laptop battery may be made by connecting four 3.6V lithium-ion batteries in series to a total voltage of 14.4V; then, two of the series-connected batteries are connected in parallel, thus increasing the total capacity of the battery pack from 2000 mAh to 4000 mAh. This connection is called "four series and two parallel", which means: two battery packs of four batteries connected in series are connected in parallel.

One battery is commonly used in watches, backup memory and cell phones. The nominal voltage of a nickel-based battery is 1.2V, an alkaline battery is 1.5V, a silver oxide battery is 1.6V, a lead-acid battery is 2V, a lithium battery is 3V, and a lithium-ion battery is 3.6V. The nominal voltage of lithium-ion polymer and other types of lithium batteries is generally 3.7V. If you want to get an uncommon voltage like 11.1V, you have to connect three of these batteries in series. With the development of modern microelectronics technology, we can now use a 3.6V lithium-ion battery to power cellular phones and low-power portable communication products. In the 1960s, mercury batteries were widely used in light meters, but now they have been completely withdrawn from the market for environmental protection reasons. The

nominal voltage of nickel-based batteries is 1.2V or 1.25V. There is no difference between them except market preference. Most commercial batteries have a voltage of 1.2V per cell; industrial batteries, aviation batteries, and military batteries still have a voltage of 1.25V per cell. Portable devices that require high power

in series

are generally powered by battery packs of two or more batteries connected in series. If high-voltage batteries are used, the size of conductors and switches can be made very small. Moderate-priced industrial power tools are generally powered by batteries with a voltage of 12V to 19.2V; while advanced power tools use batteries with a voltage of 24V to 36V to obtain greater power. The automotive industry eventually increased the voltage of the starter ignition battery from 12V (actually 14V) to 36V or even 42V. These battery packs are composed of 18 lead-acid batteries connected in series. In early hybrid cars, the battery pack used to power the car was 148V. Newer models use battery packs with voltages as high as 450V to 500V, mostly nickel-based chemistry batteries. A nickel metal hydride battery pack with a voltage of 480V is composed of 400 nickel metal hydride batteries connected in series. Some hybrid cars have also been tested with lead-acid batteries.

42-V automotive batteries are expensive and, more often than 12-V batteries, they arc more on the switch. Another problem with using high-voltage battery packs is the possibility of a single cell failing. It's like a chain. The more cells are connected in series, the higher the chance of this happening. If one cell fails, its voltage will drop. Eventually, a "broken" cell may interrupt the flow of current. Replacing a "bad" battery is not easy because the old and new cells are not compatible. Generally speaking, the capacity of a new battery is much higher than that of an old one.

Let's look at an example of a battery pack where the third cell only produces 0.6 V instead of the normal 1.2 V (Figure 1). As the operating voltage drops, it reaches the end-of-discharge point faster than a normal battery pack, and its service life is greatly reduced. Once the device cuts off due to low voltage, the remaining three intact cells cannot deliver the stored energy. At this time, the third battery still presents a large internal resistance. If there is a load at this time, the output voltage of the entire battery chain will drop significantly. In a group of serial batteries, a battery with poor performance is like a plug blocking a water pipe, which will produce huge resistance and prevent current from flowing. The third battery will also short-circuit, which will reduce the terminal voltage to 3.6V, or disconnect the battery chain and cut off the current. The performance of a battery pack depends on the performance of the worst battery in the battery pack.

Parallel connection

In order to get more power, two or more batteries can be connected in parallel. In addition to connecting batteries in parallel, another way is to use larger batteries. Due to the limitations of available batteries, this method is not suitable for all situations. In addition, large-sized batteries are not suitable for the form factor required for special batteries. Most chemical batteries can be used in parallel, and lithium-ion batteries are most suitable for parallel use. The battery pack composed of four batteries in parallel maintains a voltage of 1.2V, while the current and operating time are increased to four times.

Battery Pack Example In parallel, high impedance or "open" cells have less impact than in series, but paralleling cells reduces load capacity and runtime. This is like an engine running on only three cylinders. Short circuits can be more damaging because, in the event of a short, a faulty cell can quickly drain the other cells and start a fire (Figure 2).

Series-parallel Connections

The series-parallel connection method provides design flexibility and allows standard cell sizes to be used to achieve the required voltage and current ratings (Figure 3). It should be noted that the total power does not change when the cells are connected in different ways. Power is equal to voltage times current.

For lithium-ion batteries, series-parallel connections are common. The most common type of battery pack is the 18650 (18 mm diameter, 650 mm long). It has protection circuitry that monitors each cell in the series connection, so its maximum practical voltage is 14.4 V. This protection circuit can also be used to monitor the status of each cell in the parallel connection.

Household Batteries

The battery series and parallel connection methods discussed above are for rechargeable battery packs, in which the batteries are permanently welded together. In addition to installing several batteries in the battery compartment and connecting them in series, the above rules also apply to household batteries. When using several batteries in series, you must follow the following basic requirements:

● Keep the battery connection points clean. When using four batteries in series, there are a total of eight connection points (the connection point from the battery to the battery compartment, and the connection point from the battery compartment to the next battery). Each connection point has a certain resistance. If the connection points are increased, the performance of the entire battery pack may be affected.

● Do not mix batteries. When the battery power is low, replace all batteries. When using in series, use batteries of the same type.

● Do not charge non-rechargeable batteries. When charging non-rechargeable batteries, hydrogen is generated, which may cause an explosion.

● Pay attention to the polarity of the batteries. If the polarity of a battery is reversed, it will reduce the voltage of the entire string of batteries instead of increasing it.

● Remove batteries that have been completely discharged from the equipment that is not in use. Old batteries are more prone to leakage and corrosion. Alkaline batteries are less of a problem than carbon-zinc batteries.

●Don't put all batteries in a box, as this may cause a short circuit. A short circuit in a battery will cause heat and may cause a fire. Please put used batteries in a small plastic bag to insulate them from the outside world.

●Original battery packs like alkaline batteries can be thrown into ordinary trash cans. However, it is best to send used batteries for recycling.

How to properly connect batteries in series and parallel may sound simple, but following a few simple rules can avoid unnecessary problems.

In a battery pack, multiple cells are connected in series to get the required operating voltage. If higher capacity and higher current are required, the batteries should be connected in parallel. There are also battery packs that combine the two methods of series and parallel. A laptop battery may be made by connecting four 3.6V lithium-ion batteries in series to a total voltage of 14.4V; then, two of the series-connected batteries are connected in parallel, thus increasing the total capacity of the battery pack from 2000 mAh to 4000 mAh. This connection is called "four series and two parallel", which means: two battery packs of four batteries connected in series are connected in parallel.

One battery is commonly used in watches, backup memory and cell phones. The nominal voltage of a nickel-based battery is 1.2V, an alkaline battery is 1.5V, a silver oxide battery is 1.6V, a lead-acid battery is 2V, a lithium battery is 3V, and a lithium-ion battery is 3.6V. The nominal voltage of lithium-ion polymer and other types of lithium batteries is generally 3.7V. If you want to get an uncommon voltage like 11.1V, you have to connect three of these batteries in series. With the development of modern microelectronics technology, we can now use a 3.6V lithium-ion battery to power cellular phones and low-power portable communication products. In the 1960s, mercury batteries were widely used in light meters, but now they have been completely withdrawn from the market for environmental protection reasons. The

nominal voltage of nickel-based batteries is 1.2V or 1.25V. There is no difference between them except market preference. Most commercial batteries have a voltage of 1.2V per cell; industrial batteries, aviation batteries, and military batteries still have a voltage of 1.25V per cell. Portable devices that require high power

in series

are generally powered by battery packs of two or more batteries connected in series. If high-voltage batteries are used, the size of conductors and switches can be made very small. Moderate-priced industrial power tools are generally powered by batteries with a voltage of 12V to 19.2V; while advanced power tools use batteries with a voltage of 24V to 36V to obtain greater power. The automotive industry eventually increased the voltage of the starter ignition battery from 12V (actually 14V) to 36V or even 42V. These battery packs are composed of 18 lead-acid batteries connected in series. In early hybrid cars, the battery pack used to power the car was 148V. Newer models use battery packs with voltages as high as 450V to 500V, mostly nickel-based chemistry batteries. A nickel metal hydride battery pack with a voltage of 480V is composed of 400 nickel metal hydride batteries connected in series. Some hybrid cars have also been tested with lead-acid batteries.

42-V automotive batteries are expensive and, more often than 12-V batteries, they arc more on the switch. Another problem with using high-voltage battery packs is the possibility of a single cell failing. It's like a chain. The more cells are connected in series, the higher the chance of this happening. If one cell fails, its voltage will drop. Eventually, a "broken" cell may interrupt the flow of current. Replacing a "bad" battery is not easy because the old and new cells are not compatible. Generally speaking, the capacity of a new battery is much higher than that of an old one.

Let's look at an example of a battery pack where the third cell only produces 0.6 V instead of the normal 1.2 V (Figure 1). As the operating voltage drops, it reaches the end-of-discharge point faster than a normal battery pack, and its service life is greatly reduced. Once the device cuts off due to low voltage, the remaining three intact cells cannot deliver the stored energy. At this time, the third battery still presents a large internal resistance. If there is a load at this time, the output voltage of the entire battery chain will drop significantly. In a group of serial batteries, a battery with poor performance is like a plug blocking a water pipe, which will produce huge resistance and prevent current from flowing. The third battery will also short-circuit, which will reduce the terminal voltage to 3.6V, or disconnect the battery chain and cut off the current. The performance of a battery pack depends on the performance of the worst battery in the battery pack.

Parallel connection

In order to get more power, two or more batteries can be connected in parallel. In addition to connecting batteries in parallel, another way is to use larger batteries. Due to the limitations of available batteries, this method is not suitable for all situations. In addition, large-sized batteries are not suitable for the form factor required for special batteries. Most chemical batteries can be used in parallel, and lithium-ion batteries are most suitable for parallel use. The battery pack composed of four batteries in parallel maintains a voltage of 1.2V, while the current and operating time are increased to four times.

Battery Pack Example In parallel, high impedance or "open" cells have less impact than in series, but paralleling cells reduces load capacity and runtime. This is like an engine running on only three cylinders. Short circuits can be more damaging because, in the event of a short, a faulty cell can quickly drain the other cells and start a fire (Figure 2).

Series-parallel Connections

The series-parallel connection method provides design flexibility and allows standard cell sizes to be used to achieve the required voltage and current ratings (Figure 3). It should be noted that the total power does not change when the cells are connected in different ways. Power is equal to voltage times current.

For lithium-ion batteries, series-parallel connections are common. The most common type of battery pack is the 18650 (18 mm diameter, 650 mm long). It has protection circuitry that monitors each cell in the series connection, so its maximum practical voltage is 14.4 V. This protection circuit can also be used to monitor the status of each cell in the parallel connection.

Household Batteries

The battery series and parallel connection methods discussed above are for rechargeable battery packs, in which the batteries are permanently welded together. In addition to installing several batteries in the battery compartment and connecting them in series, the above rules also apply to household batteries. When using several batteries in series, you must follow the following basic requirements:

● Keep the battery connection points clean. When using four batteries in series, there are a total of eight connection points (the connection point from the battery to the battery compartment, and the connection point from the battery compartment to the next battery). Each connection point has a certain resistance. If the connection points are increased, the performance of the entire battery pack may be affected.

● Do not mix batteries. When the battery power is low, replace all batteries. When using in series, use batteries of the same type.

● Do not charge non-rechargeable batteries. When charging non-rechargeable batteries, hydrogen is generated, which may cause an explosion.

● Pay attention to the polarity of the batteries. If the polarity of a battery is reversed, it will reduce the voltage of the entire string of batteries instead of increasing it.

● Remove batteries that have been completely discharged from the equipment that is not in use. Old batteries are more prone to leakage and corrosion. Alkaline batteries are less of a problem than carbon-zinc batteries.

●Don't put all batteries in a box, as this may cause a short circuit. A short circuit in a battery will cause heat and may cause a fire. Please put used batteries in a small plastic bag to insulate them from the outside world.

●Original battery packs like alkaline batteries can be thrown into ordinary trash cans. However, it is best to send used batteries for recycling.