Parallel and Series – What’s Best? When Connecting Lithium Batteries

Parallel and Series connections in lithium batteries has been a tricky debate to choose from for various applications. Lithium Batteries are a clean energy source for present and future generations. Despite the advantages they offer, the users are still not completely aware of their usage and management. If the users educate themselves to effectively use the Li-ion batteries, they can gain more power from them.

Getting to know the basics can help you in understanding your battery issues well. Eventually, you can not only manage your batteries but also optimize their usage. Connecting two or more components allows you to create a circuit.

There are two basic ways to connect individual cells into a battery that is Series and parallel.

Basic types of Battery Connections

We use three basic types of batteries connections as below:

• Parallel Connection
• Series Connection
• Series-Parallel Connection

Series Connection:

Every cell has two ends i.e., positive and negative. In a series connection, the positive end of the 1^st cell is connected to the negative end of the 2^nd cell. Similarly, the positive end of the 2^nd cell is connected to the negative end of the 3^rd cell as shown in the figure.

In series, connection voltages will add and the current will be the same. For instance, if we connected 3 cells in a series having the parameters of 3.2v and 5000mah then the output will be 9.6v (3.2+3.2+3.2) and the current will be 5000mah.

The batteries would be configured in series if the positive (+) and negative (-) terminals of the battery were connected, as indicated in the below diagram.

When batteries are connected in series, the current through each wire or segment is the same, but the voltage is different, meaning that the voltages are additive.

Two 12V, 200Ah batteries, each, are connected in series then the voltage is cumulative, and the total effective Ampere-hour (Ah) would remain constant.

i.e.

12V + 12V = 24V, 200Ah

Parallel Connection:  

If the positive of the 1^st cell is connected to the positive of the 2^nd and 3^rd cells and the negative of the 1^st cell is connected to the negative of the 2^nd and 3^rd cells then it is called a parallel connection

In a parallel connection, the voltage remains the same and current will add, for example, if we connect 3 cells in parallel having the parameters of 3.2V and 5000mah each, then the output will be 3.2V and 15000mah (5000+5000+5000).

If we connect the battery’s positive (+) and negative (-) terminals, respectively as shown in the above figure. The batteries would then be set up in parallel.

While the voltage of each wire or piece of a parallel connection will be the same, the current, which is addictive, will vary.

If two batteries, each rated at 12V and 200Ah, are linked in parallel then amps-per-hour is cumulative, and the total effective voltage would remain constant.

i.e.

400Ah, 12V = 200Ah plus 200Ah.

When and how should batteries be connected in parallel and series?

When you need to double the battery’s ampere hours (Ah) rating and voltage to meet your system’s requirements.

For instance, if you need a 600Ah capacity and 24V system for installation and you have six batteries, each of which is 12V and 200Ah. Now that you have two sets of three batteries, you can connect them in series and then in parallel (as shown in the diagram above), giving you a total battery capacity of 600Ah and a level of voltage of 24V.

You can use any number of batteries to achieve various voltage levels and to improve the battery’s ampere-hour capacity.

Instructions & caution when connecting batteries in parallel and series:

• To prevent a short circuit, damage, injury, explosion, or fire, never short a battery’s Positive (+) or Negative (-) terminals together.
• To prevent charging issues and limited battery life, always connect the same voltage level and battery capacity.
• Avoid confusing the complicated wiring and connecting of batteries in series and parallel (as it may be dangerous). To be safe, always perform accurate calculations and create schematic and sketches of battery bank connections before putting them into practice.
• To prevent short circuits and potentially dangerous conditions, special attention should be paid to polarity when charging secondary batteries.
• Remove the charger once the battery is fully charged to prevent overheating (In case of a charge controller or non-automatic charger).
• The battery should always be charged at a normal temperature.
• The main cells should not be charged. In other words, avoid charging non-rechargeable batteries.
• If the battery is not being used, disconnect it from the associated load to prevent corrosion and leaking.
• Before connecting or detaching terminals, disconnect the load and the source of the battery’s charging.

Frequently Asked Questions (FAQ)

What is the purpose of connecting batteries in parallel and series?

It all depends on the system’s needs, such as whether to increase voltages by connecting batteries in series, measure battery ampere-hours (as batteries are rated in Ah rather than Amperes), or simply maintain the system as per your requirements by connecting the batteries in parallel or series-parallel.

When and how should batteries be connected in parallel?

It is useful when maintaining the same level of voltages but needing to double the battery’s ampere hours (Ah) rating or capacity.

For instance, if you need a 12V system for installation and you have two 12V, 200Ah batteries. Simply connect the two batteries in parallel so that they have a combined 400Ah capacity and the same voltage level, or 12V.

Remember that parallel battery connections deplete batteries more quickly than series battery connections.

You can achieve the same level of voltage while increasing the battery capacity in ampere-hours by connecting any number of batteries in parallel.

When Should Batteries Be Connected in Series, and How Do We Do It?

When you need to maintain the same capacity or ampere-hour (Ah) rating of batteries while doubling the voltage level to meet the demands of your system.

For instance, if you need a 24V system for installation and you have two 12V, 200Ah batteries. Simply connect the two batteries in series to obtain 24V and the same 200Ah ampere-hour rating.

Remember that series connections to batteries deplete batteries more slowly than parallel connections.

By connecting batteries in series, you may do it with any number of batteries, generating 36V, 48V, 72V DC, and so on.

Summary

While making a Lithium battery this calculation of series and parallel connections is very important. Hope you understood the parallel and series connection easily through this article. This article aims to give you a broader perspective of what you are dealing with when referring to the terms parallel and series concerning batteries.