Series vs. Parallel Battery Wiring Explained

Despite what you might think, you don’t have to be an expert to go off-grid. You do, however, need some technical know-how for safe and efficient travel. One of those must-knows is understanding series vs. parallel battery wiring. In this blog, we’re breaking down circuit theory, why it’s important, and how these different configurations impact overall system capabilities. 

Why is Proper Battery Configuration Important? 

Proper battery configuration is key to lithium battery safety and optimal performance. In fact, we consider it a foundational skill for anyone wanting to pursue off-grid travel or power appliances while venturing out in their van, RV, or boat. By understanding series vs. parallel wiring—and circuit theory as a whole—you can determine how each configuration affects voltage, current, and capacity. 

Without the proper battery configuration for your particular application and device needs, you can cause batteries to become overworked, discharged at a higher rate, and overcharged. Not only can this scenario lead to your battery failing prematurely. It can also cause an unstable and unsafe situation. 

First: Circuit Theory Defined 

Circuit theory refers to the understanding of how electrical circuits work. It analyzes the network of devices or equipment needed to connect the source of energy to power devices, process information, or transmit signals. 

Understanding Series vs. Parallel Battery Wiring 

Whatever your experience level is for off-grid travel and lithium battery usage, understanding the practical applications of parallel and series configurations provides you with solid knowledge for smooth travels.

Let’s get into it. 

Series Wiring 

In a series wiring configuration, the individual battery terminals are connected positive to negative in strings of up to four batteries. The basic principle for series is that the voltage increases, but the capacity remains constant. For example, if you have two 100 Ah batteries wired in series, you’d get a total of 100 Ah at 24 volts direct current (DC). 

Series configuration effects include: 

• Energy (measured in watt-hours) will increase incrementally by the amount held in each battery. 
• Capacity (measured in Ah) will remain the same as the individual battery rating. 
• Volts (measured in volts DC) will increase incrementally by the individual battery rating. 
• Current (measured in amps) will maintain charge or discharge rates by the amount held in each individual battery.

Parallel Wiring

In a parallel wiring configuration, the individual battery terminals are connected positive to positive and negative to negative in strings of up to four batteries. The basic principle for parallel is that the voltage remains constant, but the capacity increases. For example, if you have two 120 Ah batteries wired in parallel, you’d get a total of 240 Ah at 12 volts DC. 

Parallel configuration effects include: 

• Energy (measured in watt-hours) will increase incrementally by the amount held in each battery. 
• Capacity (measured in Ah) will increase incrementally by the amount held in each battery. 
• Volts (measured in volts DC) will remain the same as the individual battery rating. 
• Current (measured in amps) will increase charge or discharge rates incrementally by the amount held in each battery. 

Of note in parallel: it’s best to pick up the positive terminal at one end of the single parallel string and the negative terminal from the opposite end. This will help balance the current and voltage running through the string during charge or discharge.

A Side Bar on Bus Bars 

Bus bars are the preferred connection method for both series and parallel wiring configurations. In contrast, wire interconnections are susceptible to loose connections, loose lugs, and unequal length, all of which can add additional resistance to the wiring configuration. 

Applications and Series Configurations 

Deciding to wire in series or parallel depends on your application and device needs, whether higher voltage, increased capacity, or a combination. For optimal setup, you need to consider factors like battery chemistry, available space, balancing, and application requirements. 

We’ve broken it down into three common applications: RV, marine, and off-grid solar systems. 

Pros and Cons of Series Wiring 

Pros: 

• More voltage to power larger applications like air conditioning units, navigation equipment, and high-voltage connections and inverters. 
• Allows for quicker voltage charges and fewer losses with cabling. 
• Ideal for high wattage demands. 
• Optimal for systems with specific voltage requirements. 

Cons: 

• Need to consider battery balancing for even charging/discharging.  
• Series wiring takes up more physical space.
• Need to ensure all solar panels or batteries have similar characteristics. 
• More susceptible to reduced output if there’s shading on one of the panels (specifically for solar systems). 

Pros and Cons of Parallel Wiring

Pros: 

• Longer battery runtime for RV electrical systems, marine vessels, or off-grid solar setups. 
• Less concern with battery balancing, but still need batteries of the same capacity. 
• More space efficient. 
• Extends the battery runtime for onboard equipment. 
• Can be used as a backup power source. 
• Increases the overall capacity of off-grid systems 

Cons: 

• May not be the best option for applications with higher voltage requirements. 
• Need similar characteristics to maintain balance. 

Although series and parallel wiring can be used for any of these applications, your configuration choice ultimately depends on what type of voltage your system requires to run optimally. Understanding the difference between the two ensures the safest, most reliable setup for your system. 

Empowering You to Explore More 

No matter how long you’ve been doing it, off-grid travel usually requires trial and error. Having foundational knowledge and being as prepared as possible ensures the smoothest adventuring possible. With a solid understanding of series vs. parallel battery wiring, you can choose the optimal configuration to power the pursuit—wherever the wanderlust takes you. 

Explore the entire Expion360 lithium battery line here.