Series Vs. Parallel Battery Connections Explained

Ever found yourself immersed in a weekend project, like setting up a backup power system for your business or setting up a solar power system, only to hit a roadblock when it comes to connecting batteries? The excitement of creating a reliable and efficient energy source can quickly turn into a maze of decisions when you encounter the dilemma of series versus parallel battery connections. As you strive to optimize your power setup, the need to understand the disparities between these configurations becomes apparent.

When connecting multiple batteries, you may have them placed in a series or parallel depending on the power and voltage needs of the application.

Key Takeaways

• Positive-to-positive connections (parallel) offer an increase in the overall output of power.
• Positive-to-negative connections (series) provide an increased voltage output.
• The number of batteries used for a series vs parallel connection is based on battery capacity, battery voltage, and the application.

Batteries in Series vs Parallel

Batteries serve various purposes, such as powering systems, offering backup during emergencies, or storing renewable energy like solar and wind power for grid use. In many cases, multiple batteries are required for these applications, with the batteries interconnected both among themselves and with the target device. Two common configurations for integrating these batteries are series connections and parallel connections, and the choice between them depends on how the positive and negative terminals are interconnected through the cable harness.

Using multiple batteries is ideal when the battery chemistry cannot be changed to offer higher power or voltage for the application. This configuration is also used when a larger battery cannot be placed in the device.

Batteries in Series: Pros and Cons

With batteries in a series, the voltage increases by double. So two 6-volt batteries will provide 12 volts while two 12-volt batteries will offer 24 volts. For a series configuration, batteries must have the same voltage for a safe connection to prevent damage. A 6-volt battery should never be connected to a 12-volt battery in a series placement. Also, keep in mind that even with the increase in voltage, the amp-hour capacity does not change.

There are various advantages to batteries in a series. Series configurations are necessary for high-voltage applications. The load on the batteries is spread across them equally, helping to reduce stress while providing an increase in overall battery efficiency. For alternative power storage or backup power, a series configuration can store more energy for extended periods of time.

Overcharging and undercharging are two types of disadvantages to a series configuration. If one battery cell is weaker in the series, charging may continue in the attempt to fill the weaker battery while the rest have full capacity. Another instance is when the charge is stopped when batteries with more capacity are fully charged without the weaker battery reaching its top level. So the weaker battery remains undercharged. Battery balancing is usually required to prevent overcharging or undercharging which can degrade the battery pack's performance.

Another disadvantage is that battery cells can discharge at different rates. Batteries can discharge quickly and die before others, as this problem may lead to the system shutdown. Only four batteries can be placed into a series unless the batteries have lead cell chemistries. There is no limit to the number of lead cell batteries in a series configuration.



Batteries in Parallel: Pros and Cons