Series Vs. Parallel Battery | How To Choose?

Before purchasing batteries or connecting devices to batteries, one important consideration we often need to think about is the method of connection. Different connection methods yield different results, for example, connecting in series can increase voltage, while connecting in parallel maintains voltage. So, when should we choose a series connection, and when should we choose a parallel connection? How can we implement them? What are the differences between them? I believe you might have some answers in mind too. Let’s take a look together and see if this content aligns with your thoughts.

Series And Parallel Battery Display

What Is A Series Battery?

Connecting batteries in series is generally done to maintain a constant current while achieving a higher output voltage. By connecting two or more batteries end to end in sequence to form a closed circuit, a higher voltage can be obtained. To put it simply, the positive terminal of the first battery is connected to the negative terminal of the second battery, and then the positive terminal of the second battery is connected to the negative terminal of the third battery. This sequential connection adds up to the required voltage. The total voltage is the sum of the voltages of all the batteries in this circuit.

As shown in the diagram, Delong’s 12.8V lithium iron phosphate battery pack is composed of 4 cells connected in series, each with a voltage of 3.2V. 3.2V * 4 = 12.8V.

12.8V Lifepo4 Battery

Advantage

• Increase Voltage

The greatest benefit of connecting batteries in series is that it can increase the circuit’s voltage, which is also the main reason why we choose series connection. When we power devices that require higher voltages, series connection is the preferred method.

• Current Remains Unchanged

When batteries are connected in series, the total voltage of the circuit is the sum of the voltages of all the batteries, but the current remains the same, still being the current of a single battery. In other words, the battery pack obtained by connecting batteries in series does not change the continuous power supply time of the equipment. For example, when 4 pieces of 12V 7Ah lithium batteries are connected in series, you can obtain a 48V 7Ah lithium battery pack.

• Without Converter

When the voltage required by the device is higher than the voltage of a single battery, series-connected batteries can be directly connected to the device without the need for a booster converter.

• Simple Circuit

The circuit for connecting batteries in series is relatively simple and easy to implement. In addition, the wires used for series connection are relatively thin, which can save on wiring expenses. Furthermore, when a circuit malfunction occurs, the problem can be quickly detected.

Disadvantage

To connect in series, it is important to ensure the consistency of each battery’s parameters, such as the same voltage and rated capacity.

If any one battery malfunctions, the entire circuit will be affected, such as voltage drop or the entire battery pack becoming unusable.

When connecting to low-voltage devices, a converter should be used.

What Is a Parallel Battery?

Connecting the positive poles of two or more batteries and the negative poles together to form a closed circuit is called a parallel circuit. Parallel batteries can increase capacity and extend the time for supplying current to a device while keeping the circuit voltage constant. For example, home energy storage systems often connect batteries in parallel to extend your system’s usage time. As shown in the example Delong HS51200-10.

Five packs of 51.2V 200Ah 10kWh lithium batteries are connected in parallel to achieve 51.2V 50kWh.

Advantage

• Increase Current

Parallel batteries can increase the output current of a circuit, meeting the needs of devices that require large current. The increase in current means that the storage capacity also increases, which can extend the continuous working time of the batteries.

• Voltage Remains Unchanged

Parallel batteries will not change the overall voltage of the circuit and will not affect devices with low voltage.

• Service Life

In a parallel battery pack, even if one of the batteries fails, the remaining batteries can still continue to output power, making it suitable for use with devices that cannot afford any power interruption.

Disadvantage

Parallel-connected batteries require high consistency. If the parameters of a battery deviate significantly from the overall standard, it can easily affect the lifespan and performance of the entire battery pack. When a circuit failure occurs, it takes longer to detect the source of the problem.

Comparison: Series vs Parallel Battery

The simple description above roughly explains the meanings of series and parallel connections. Next, let’s list the differences between them in a straightforward manner.

• Connection Method

Series connection is to connect the positive and negative terminals of the batteries in sequence.

Parallel connection is to connect the positive terminals together and the negative terminals together.

• Current

In series connection: The total current of the circuit remains consistent with the value of a single battery.

In parallel connection: The total current of the circuit increases and is the sum of the currents of all individual batteries.

• Voltage

In series connection: The total voltage of the circuit is the sum of the voltages of all individual batteries, resulting in an increased output voltage of the circuit.

In parallel connection: The circuit voltage remains constant and is equal to the value of a single battery.

• Resistance

When batteries are connected in series, the voltage of the entire circuit increases, and the internal resistance also increases. The total internal resistance is the sum of the internal resistance of all the batteries.

When batteries are connected in parallel, the output voltage of the entire circuit remains unchanged, but the internal resistance decreases.

• Energy

Assuming the parameters of the batteries are the same, it is known that when batteries are connected in series, the voltage increases while the current remains the same; when connected in parallel, the voltage remains the same while the current increases. Therefore, in ideal conditions:

The total energy of batteries connected in series basically remains unchanged.

The total energy of batteries connected in parallel increases.

• Wire

In series connection: The cables used are relatively thin.

In parallel connection: Large-capacity cables are required.

• Life

The lifespan of a series-connected battery pack depends on the battery with the weakest performance. When this battery reaches the end of its lifespan, the entire battery pack cannot function. The battery pack and the single battery are inextricably linked in terms of damage.

Conversely, if a battery in a parallel-connected battery pack fails, it will not cause the entire circuit to stop working, as the other batteries will continue to function normally. Although the overall performance is affected to some extent.

In other words, the lifespan of a parallel battery pack is longer than that of a single battery as well as a series battery pack. Of course, this is under ideal conditions, as actual application will be influenced by various factors such as temperature, battery chemistry, and charging habits.

• Safety

When the consistency of the batteries used is poor, connecting them in series can easily cause battery imbalance. Weaker performing batteries are prone to over-discharge or reverse charging, leading to battery damage. Additionally, if any one battery fails, the entire circuit will shut down. For certain devices that cannot tolerate power outages, this would be a significant blow.

Parallel-connected batteries require high consistency, and the performance of individual batteries is best kept at the same level. If a battery’s performance is weaker, problems with overcharging or discharging may occur.

Therefore, whether in series or parallel, it is essential to be extremely cautious about overcharging and discharging the batteries.

• Common use

Series batteries are usually used in devices and applications that require high voltage and low current, such as high-voltage portable electronic devices, electric bicycles, electric skateboards, specific voltage medical devices and scientific instruments, and backup energy systems for industrial and commercial use.

Parallel batteries are typically used in devices and applications that require low voltage and high current, such as mobile device chargers, emergency power supply systems, RV power supplies, home backup power sources, and portable power supplies.

Series vs Parallel Battery, Which is Best For You?

In fact, the above content has already provided the answer. Series and parallel connections have their own advantages and disadvantages, and the choice of which connection method depends on the needs of your devices. If your device operates at a higher voltage, a series connection can meet your needs. If you want the battery to run longer, then it is recommended that you choose a parallel connection.

12 100Ah Lifepo4 Battery Connection

How To Set Up Your Battery In Series？

1. Determine the voltage value required for devices or applications that need to be connected to the power supply; 
2. Select batteries of the same type with high consistency (such as voltage, current, charging and discharging rates, etc.); 
3. Arrange all the batteries in order, with the positive and negative poles close together; 
4. Use connecting wires to connect the positive pole of the first battery to the negative pole of the next battery, and repeat this operation; 
5. Check whether each battery is tightly connected to prevent short circuits and other situations; 
6. Test with a multimeter whether the total voltage of the entire battery pack meets the set value; 
7. Connect the positive and negative poles of the first and last sections of the battery pack to the positive and negative poles of the device, respectively.

Connect Batteries in Series Delong

How To Set Up Your Battery In Parallel？

1. Determine the current required by the device or application and prepare wires with a sufficient thickness.
2. Select batteries of the same type with high consistency in voltage, capacity, and degree of aging.
3. Connect the positive terminals of all batteries in sequence, and do the same for the negative terminals.
4. Check the tightness of each connection point to prevent short circuits.
5. Connect the positive and negative terminals of the first and last sections of the battery pack to the device.
6. Finally, check if the system is functioning normally.

Connect Batteries in Parallel Delong

Delong 51.2V Lithium Battery Parallel Diagram LVM101515L

Except Series or Parallel, Can I Connect Battery In Series-Parallel？

Of course. In addition to series and parallel connections, we can also choose to first connect in series and then in parallel. This way, not only can we achieve a specific voltage value, but we can also increase the capacity, achieving a “two-handed” effect. The series-parallel connection method is better suited to the practical needs for voltage and capacity in daily life, allowing devices to operate more stably. 

For example, the internal cells of the Delong 12Ah lithium battery are connected in a 4S2P configuration (S-Series, P-Parallel).

FAQ

How To Charge Batteries In Series Or Parallel Circuits?

Whether in series or in parallel, when charging the batteries, it is necessary to use a charger that matches the battery system. 

For example, when charging batteries in series, it is recommended to use a matched charger for constant current followed by constant voltage charging. It is best to charge each battery separately if possible. For batteries in parallel, it is important to maintain a uniform charging state. 

In addition, regardless of whether in series or in parallel, it is best to monitor the battery status at all times to avoid overcharging and over-discharging, which helps to extend the battery’s lifespan.

How Many Batteries Can Be Connected In Series Or Parallel At The Same Time?

Connecting batteries in series will increase the circuit’s voltage, so there is a certain limit to the number of batteries that can be connected in series. If you need to know the maximum number of batteries that can be connected in series, we recommend consulting the battery manufacturer and connecting within this range. 

For example, for the Delong 12V 100Ah lithium iron phosphate battery, currently up to 4 batteries can be connected in series to obtain a 48V 100Ah battery pack.

In theory, there is no limit to the number of batteries connected in parallel. However, in practical applications, you need to consider factors such as the type and capacity of the batteries, equipment requirements, application environment, and safety. If you are unsure, you can also contact your battery manufacturer for confirmation or seek assistance from experienced technical personnel.

Can Batteries Of Different Voltages Be Connected In Series Or Parallel?

Before connecting batteries in series or parallel, we generally check the voltage of each battery to ensure their consistency. The higher the consistency of the batteries, the better the safety performance and longer lifespan of the series or parallel battery pack. The greater the differences in the batteries, the higher the risk of overcharging or over-discharging in the series or parallel battery pack, and the greater the probability of battery damage.

Therefore, for safety reasons, we do not recommend connecting batteries with different voltages in series or parallel.

Can Batteries Of Different Capacities Be Connected In Parallel?

We do not recommend that you use batteries of different capacities in parallel. This is because batteries with different capacities have different internal resistances, current loads, charging/discharging efficiencies, and heat generation, leading to an imbalance. During parallel usage, it is difficult to ensure the stable performance of the battery pack as a whole. The lifespan of the lower capacity batteries is easily compromised, thereby affecting the lifespan of the entire battery pack.

Conclusion

The above is about the content of series vs. parallel. If you have different opinions, feel free to leave your comments!