Serial Battery Connection | How to Connect Batteries in Series, Parallel

A Battery is a device that converts Chemical Energy into Electrical Energy. You might have come across different types of batteries in cars, bikes, flashlights, mobile phones, UPS, and Inverter systems. There will be a situation where you want to connect some batteries in Series for a specific purpose or application. But what is the need for connecting batteries in Series? How to make a Serial Battery Connection? What are the requirements for connecting batteries in Series? What is the outcome of batteries connected in series? In this article, we will understand the importance of a series battery connection.

Battery and its Applications

Batteries are amazing little devices. They are chemical devices that convert chemical energy into electrical energy. It is one of the easiest ways to store indirect electrical energy as it is very difficult to store it directly (except supercapacitors, but they are on a different economic scale).

The best thing about batteries is that they are available in different shapes, sizes, capacities, and types. There are Primary Batteries, which are one-time use batteries, and Secondary Batteries, which are rechargeable for using multiple times. You can select the right style of battery depending on the application.

Speaking of applications of batteries, initially, they were used in flashlights and toys. But the growth in the automobile industry led to the development of an auto cranking system, which required a starter motor and a battery. Hence, the usage of batteries in cars increased quite exponentially.

The next important thing that led to battery-operated devices is the invention of Transistors and subsequently transistor radios. This made the large tube based radios into small pocket-sized portable radios that run on batteries.

Today, the battery has become a very important part of the economy and it is more essential than ever. Smartphones, laptops, tablets, emergency lamps, smoke detectors, etc. are some of the popular household applications that use batteries.

Automobiles continue to use batteries for starting them as well as powering some essential electrical circuits such as lighting, audio, remote locking, etc. To reduce the carbon emissions from automobiles, manufacturers started developing hybrid electric as well as fully electric cars and bikes. Hybrid vehicles use small batteries to aid the internal combustion engine. Fully electric vehicles on the other hand completely run on batteries.

The importance of renewable energy has also seen significant growth in the last decade. Using solar energy as an alternative to the regular grid led to the usage of a battery-based energy storage system.

Different Ways to Connect Batteries

Whenever you are working with batteries, you will come across a situation where you have to connect multiple batteries in series, parallel, or a combination of series-parallel.

These are the three common ways to connect batteries depending on the application.

• Series
• Parallel
• Series – Parallel

But what is the use of such connections? What are the applications for Serial Battery Connection or Parallel Battery Connection? What is the advantage of Series – Parallel Battery Connection? Let us try to understand all the different types of battery connections one by one.

How to Make a Serial Battery Connection?

Let us start with the concept of “connecting Multiple Batteries” with a series connection. Assume you have two batteries. If you connect the positive terminal (+) of the second battery to the negative terminal (-) of the first battery, then the batteries are said to be connected in series.

In Serial Battery Connection, we take the output at the positive terminal (+) of the first battery and the negative terminal of the second battery (-). The following image shows the electrical symbol for connecting two batteries in series.

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We can apply this method to any type of battery, provided both the batteries are of the same type (same voltage, capacity, and size). The following image shows a series battery connection of similar batteries.

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Although the above example shows only two batteries connected in series, you can connect any number of batteries in series.

Important Notes Related to Series Battery Connection

• When we connect two batteries in series, the output voltage is double that of the individual battery. For example, if you connect two 12V batteries in series, the output voltage becomes 24V. Similarly, for three batteries in series, it is 36V and for four batteries in series, it is 48V, and so on.
• In general, if V₁ is the voltage of the first battery, V₂ for the second, and V_n for the nth battery, then the output voltage when n similar batteries are connected in series is

• Another important specification of batteries is their capacity, which is rated in mAh (Milli Ampere-hour) for small batteries and Ah (Ampere-hour) for larger batteries. For serial battery connection, the overall capacity of the system remains the same as the individual capacity of a battery.
• For example, if we connect two 12V batteries in series which are rated for 150Ah capacity each, then the effective capacity of the series connection is still 150Ah. Only the voltage is added in the series connection.
• As we saw from the above calculations, connecting batteries in series will add the individual voltages but the overall capacity remains the same. So, if you need a higher voltage system in your application, such as in solar or inverter applications, you can connect multiple batteries in series. 24V and higher voltage systems are common in high-power solar installations. 48V system is becoming extremely popular in electric vehicles, especially bikes.
• Another important thing about the serial battery connection is the wire gauge. As we are doubling the voltage with the same capacity, you can use a thinner wire (higher AWG number).

How to Make a Parallel Battery Connection?

The next important multiple battery connections is the parallel connection. Let us understand this directly with an example. Assume you have two batteries with similar ratings. To make a parallel connection, we have to connect the positive terminal (+) of the first battery with the positive terminal of the second battery.

Similarly, we have to connect the negative terminal (-) of the first battery with the negative terminal of the second battery. The following image shows the electric symbol representation of two batteries connected in parallel.

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Just like the series connection, the batteries in parallel connection must also have the same ratings (same type, voltage, and capacity). The following image shows parallel battery connection for similar battery types.

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If you want to connect more than two batteries in parallel, you can do provided they are of the same type.

Important Notes Related to Parallel Battery Connection

• When we connect two batteries in parallel, the effective voltage of the system is the same as that of the individual battery. For example, if we connect two 12V batteries in parallel, the output voltage is still 12V.
• Even if we connect ‘n’ number of batteries in parallel, the overall voltage will still be the same as that of the individual battery.
• But what adds up in parallel battery connection is the current or the capacity of the battery. If we connect two 12V batteries in parallel which are rated for 150Ah capacity, the overall voltage remains 12V but the effective capacity of the system becomes 300Ah.
• But where is parallel battery connection useful? If you want to have a large battery capacity to drive loads for a longer time, then you can connect batteries in parallel. For example, if a 12V 150Ah battery can last for 1hr when connected to a load, connecting two in parallel will essentially double the capacity and hence it can last for 2hrs.
• As we are doubling the capacity of the battery in a parallel connection, you have to use a thicker wire (lower AWG number) to support the increased current capabilities.

What is Series – Parallel Battery Connection?

Is it possible to mix the series and parallel battery connections? Absolutely yes. With a combination of series – parallel connection, you can effectively add up both the voltage as well as the capacity.

For example, if you have four 12V – 150Ah batteries, you can connect the first two batteries in series and also the third and fourth batteries in series respectively. This will essentially make two 24V systems with 150Ah capacities.

Now, we can connect these two systems in parallel to add their capacities. So, the final values of the system are 24V and 300Ah.

Such series – parallel connections of batteries are extremely common in solar energy storage banks and large inverter systems.

Important Tips and Tricks Connecting Multiple Batteries

As mentioned earlier, batteries are chemical devices that can convert chemical energy into electrical energy. Similar to any other chemicals, you have to be extremely careful when working with batteries and any mishandling will be very dangerous.

So, here are some important tips and tricks for you if you are working with batteries in general.

• Every battery has two terminals: positive (+) and negative (-). We connect the load across these terminals. Never short the positive and negative terminals of the battery. This is extremely dangerous and might even cause a fire or explosion.
• Whenever you are connecting multiple batteries in series or parallel connection, always select similar batteries with identical voltage and capacity. Never connect two batteries with dissimilar voltage or Ah ratings.
• Almost all batteries will have a marking for the positive and negative terminals with ‘+’ and ‘-’ signs. Take a note of these polarities while making series or parallel battery connections.
• Primary batteries are non-rechargeable. They are good for one-time usage and after that, you have to properly dispose of them (preferably with a recycling facility). Do not try to recharge primary batteries. They are not designed for recharging and can cause a fire if recharged.
• Secondary batteries are rechargeable. Make sure that you select an appropriate charger for recharging such batteries. Disconnect the charger once the batteries are fully charged.
• If you connect batteries in series or parallel, make a note of the effective voltage and capacity. These numbers will come in handy while selecting the charger.
• When you are not using the system, you can disconnect the load from the batteries so that they don’t get discharged due to leakage charge and also stop corrosion.
• While connecting multiple batteries in series, parallel, or a combination of series – parallel connections, it is better to make a proper schematic of the connection before proceeding. You can double-check all the connections in the schematic for any wrong connections or short circuits.

Conclusion

Batteries are quite essential devices to store energy. An extremely useful point about batteries is that you can connect them in series or parallel depending on your application. We have seen how to make a serial battery connection and some important points related when connecting batteries in series. We have also seen how parallel battery connection works. The beauty of batteries is that you can combine the series and parallel connections if you need them.