Series, Parallel, and Series-Parallel Connections of Batteries
Introduction
Individual batteries are typically too small in terms of either storage capacity or voltage. Storage capacities often need to be increased to deal with battery maintenance issues or to extend operating times for attached loads.
Voltages may need to be increased to reduce system amperage through various components or to meet charge controller requirements. Reaching the necessary electrical system requirements can be easily accomplished by connecting the batteries in the appropriate manner.
Battery Connection Types
You can connect your batteries in either of the following:
- Series connection
- Parallel connection
- Series-parallel connection
Series connection results in voltages adding and amperage remaining the same while parallel connection results in amperages adding and voltages remaining the same. Series-parallel connection results in both voltage and amperage adding.
Precautions & Rules
Rule #1: Safety First
Avoid short-circuiting the battery terminals to prevent irreversible damage to the system and battery caused by current bursts.
Verify polarity before wiring to avoid irreversible battery damage due to polarity reversal.
To ensure safe and reliable operation of the system, please follow the manufacturer’s recommended torque specifications when securing cable connections. Over-tightening can result in terminal breakage, while loose connections can lead to terminal meltdown or fire.
Rule #2: Balance Batteries Prior to Connection
Before connecting batteries in series or parallel, it is important to balance them to reduce voltage differences and optimize their performance. For lithium batteries, visit Lithium Battery Balancing.
Rule #3: Maintain All Components to Be as Identical as Possible
Wiring the batteries up to achieve the necessary capacity is akin to the internal battery wiring used to create the battery itself from the individual cells. Special consideration must be paid to this external interconnection however. A key design goal for battery banks is to maintain all components to be as identical as possible so as to reduce wear on the batteries. This includes:
- Interconnection cable length
- Battery capacities
- Interconnection fuse ratings
Addressing the above concerns, variation in cable length will cause different resistances between batteries. This will lead to disproportionate charging between bank members. Likewise, differing capacities will cause the batteries to constantly attempt to equalize with one another leading to early battery death.
Do not connect batteries with different chemistries, rated capacities, nominal voltages, brands, or models in parallel, series, or series-parallel. This can result in potential damage to the batteries and the connected devices, and can also pose safety risks.
The cables between each connected battery should be of equal length to ensure that all batteries can work equally together.
Series Connection
Connecting batteries in series adds the voltage without changing the amperage or capacity of the battery system. To wire multiple batteries in series, connect the negative terminal (-) of one battery to the positive terminal (+) of another, and do the same to the rest.
Take Renogy 12V 200Ah Core Series LiFePO4 Battery as an example. You can connect up to 4 such batteries in series.
In this system, the system voltage and current are calculated as follows:
System Voltage = V1 + V2 + V3 + V4 = 12.8V + 12.8V + 12.8V + 12.8V = 51.2V
System Capacity = 200Ah
Parallel Connection
Connecting batteries in parallel adds the amperage or capacity without changing the voltage of the battery system. To wire multiple batteries in parallel, connect the negative terminal (-) of one battery to the negative terminal (-) of another, and do the same to the positive terminals (+).
For example, you can connect four Renogy 12V 200Ah Core Series LiFePO4 Batteries in parallel.
In this system, the system voltage and current are calculated as follows:
System Voltage = 12.8V
System Capacity = Battery 1 + Battery 2 + Battery 3 + Battery 4
= 200Ah + 200 Ah + 200Ah + 200 Ah = 800Ah
Series-Parallel Connection
Series-parallel connection is required when you need to increase both the system voltage and amperage. A series-parallel system is a combination of both series and parallel connections, forming a series-parallel circuit. Some components are connected in series, while others are connected in parallel, resulting in a complex circuit of interconnected devices and batteries.
For example, you can combine two pairs of batteries by connecting them in series, and then connect these series-connected pairs in parallel. This arrangement is referred to as a series-parallel connection of batteries.
In this system,
System Voltage = 12.8V + 12.8V = 25.6V
System Capacity = 200Ah + 200 Ah = 400Ah
FAQ
Q1: How Many Batteries Can You Wire In Series, Parallel, or Series-Parallel?
The number of batteries you can wire in series, parallel, or series-parallel depends on the specific application and the capabilities of the battery bank you are building. For details, refer to the user manual of the specific battery or contact the battery manufacturer if necessary.
For example, you can connect Renogy 12V 100Ah Smart Lithium Iron Phosphate Battery in parallel.
Q2: Does the Connection Method Affect the Lifecycle of a Battery?
It depends. When batteries are wired in series, their overall voltage increases, but they are limited by the weakest battery in the series, which can lead to reduced performance and lifespan if one battery fails prematurely. On the other hand, parallel connections can distribute the load among multiple batteries, but it also increases the risk of imbalances between batteries, affecting their capacity and potentially shortening their lifespan.
To ensure optimal battery performance and longevity, it is essential to properly match batteries with similar characteristics, including capacity, voltage, and chemistry, when connecting them in series, parallel, or series-parallel configurations.
Q3: How Should I Maintain a Series-Parallel Battery System?
Regular monitoring and maintenance are crucial for a series-parallel battery system. It is essential to ensure that all batteries are functioning properly and that there are no imbalances in voltage or capacity. Periodically checking individual battery performance and replacing any faulty batteries promptly can help prolong the overall lifespan of the battery system.
Additionally, follow the manufacturer's guidelines for charging and discharging to optimize battery performance and longevity.
