How to Connect Batteries in Series vs Parallel - Ultimate DIY Guide
Wondering whether to connect your batteries in series or parallel to give your battery bank a little boost? In this post we’ll walk you through each so you know the difference and can connect batteries the way you want them.
If you're thinking about adding more than one battery to your house battery bank, then you've likely come across the idea of connecting batteries in series vs parallel. The way batteries are connected together can dramatically influence the performance and efficiency of the devices they power.
Both configurations have unique attributes and are suited to different types of circumstances. Through this post, we will help you understand how they differ, their implications on battery performance and where each configuration is most appropriately used.
This understanding can equip you to make informed decisions and optimize your devices' performance, ensuring that you truly harness the power within your batteries.
Whether you want to increase the capacity of your RV, fishing boat or golf cart battery bank, you’re going to want to make sure you know the pros and cons of each and which wiring situation is best for your application.
- Wiring your batteries in series vs parallel can have positive benefits for your power system depending on your device operating voltage requirement.
- Wiring batteries in series will increase the system voltage while keeping both the amp hours and current (amps) the same. You achieve this by connecting the positive terminals of one battery to the negative terminals of the other, and vice versa. This is common with trolling motors and golf cart applications.
- Wiring batteries in parallel will increase the battery bank capacity (amp hours) while keeping the voltage in the electrical system them same. You achieve this by connecting both batteries’ positive terminals together and likewise with the negative terminals. This is common in RV applications.
- In large electrical systems you may combine both parallel connected batteries that are also connected in series. This is more common in larger RVs and trailers.
What’s the difference between wiring batteries in series and parallel?
Wiring batteries in series involves connecting them end-to-end, effectively boosting the overall voltage while maintaining the same capacity. Conversely, wiring batteries in parallel means connecting all positive terminals together and all negative terminals together, which increases the total capacity while keeping the voltage constant.
The choice between series and parallel configurations ultimately depends on whether your power system requires a higher voltage or you want to have longer battery life, respectively.
So let's get into what each type of wiring can do for your power needs.
Wiring Batteries In Series
Wiring batteries in series is a technique used to increase the total voltage output of a battery system, while maintaining the same capacity (also known as ampere-hours or Amp Hours, abbreviated Ah).
This is really only advised when you know that your RV, fishing boat or golf cart requires higher voltage and you only have access to lower voltage batteries.
For example, many of the best trolling motors are 36V. As such, you can purchase one of our 36V batteries specifically designed to power your trolling motor.
Or you could take three 12V batteries and connect them in series to create a larger battery bank that has voltage required by the device operating at 36V.
12V + 12V + 12V = 36V (@100 Ah)
When batteries are connected in series, it means the positive terminal of a battery is connected to the negative terminal of the next, creating a chain or series of batteries. Depending on how many batteries you have in your battery bank, this increases the battery bank’s voltage while keeping the total battery capacity the same.
For instance, if you wire three 12-volt batteries rated at 100 Ah in series, the total voltage output becomes 36 volts, while the capacity remains at 100 Ah.
This configuration is beneficial for devices or applications that require a higher voltage to function efficiently. This is why you often see batteries in series in devices like trolling motors, golf carts and larger RVs.
An advantage of this, aside from ensuring you have the device operating at its required voltage, is that series connections reduce the current, or amps, that flow through the wires. Thus you can use thinner wires between your electronic devices in your power system.
However, there is a key limitation to consider with this configuration. Since the batteries are connected like dominoes in a chain, if one battery fails or gets disconnected, it interrupts the entire circuit, and the device stops working.
So, while series configuration effectively boosts voltage, it's essential to ensure that all batteries in the chain are in good condition to prevent a total system shutdown.
Further, when wiring batteries in series you must ensure that all of the batteries connected are of the same voltage. In other words, do not try to connect a 12V battery in series with a 24V battery to attain 36 volts.
And you must also be sure that the battery chemistry of all batteries in the series connections are the same. So you cannot wire a flooded lead acid battery in series to an AGM or lithium battery.
Advantages of wiring batteries in Series
There are several key advantages to wiring batteries in series:
- Increased Voltage: Wiring batteries in series results in a higher total system battery voltage, which is essential for powering devices that require more electric force.
- Lower current: Wiring batteries in series will increase the voltage while keeping the total current lower. This will allow you to use thinner wiring throughout the power system.
- Utilization of Smaller Batteries: By wiring smaller batteries in series, one can achieve the desired voltage without needing to source a larger, potentially more expensive, battery.
- Flexibility in Design: Using a series configuration allows for more flexibility in designing the power source for a device, especially when space is a constraint. Batteries can be arranged in different ways as long as they maintain the series connection.
- Cost Efficiency: It can sometimes be more cost-effective to wire multiple lower-voltage batteries in series to achieve the required voltage rather than purchasing a single high-voltage battery.
Disadvantages of wiring batteries in Series
There are also a few disadvantages of wiring batteries in series.
- Failure of One Battery: If one battery in a series configuration fails or becomes disconnected, the entire chain breaks and the device stops working, similar to a broken link in a chain.
- Uneven Discharge and Recharge: Over time, slight differences in battery capacity, resistance, or self-discharge rates can lead to uneven discharge and recharge among the batteries in a series, potentially reducing overall performance.
- Complex Charging: Each battery in a series configuration might not receive equal charging, due to variations in internal resistance, age, or capacity, leading to some batteries being overcharged while others may be undercharged.
- Balancing Issues: To ensure that each battery in a series chain is charged and discharged evenly, a battery management system (BMS) is often required, adding to the complexity and cost. Our lithium batteries have these built into them.
- Increased Risk: The higher battery voltage output from a series configuration could pose a greater risk of electrical shock or fire if not properly managed. While significantly less voltage than your standard 110 V power outlet, 36V or 48V battery voltage can still be dangerous.
- Mismatched Batteries: It's essential to use identical batteries (same type, capacity, charge level, brand, and ideally from the same production batch) in a series configuration. Using mismatched batteries can lead to premature failure or decreased performance.
Wiring Batteries in Parallel
Wiring batteries in parallel is a common configuration that serves to increase the total amp hour capacity, or longevity, of a battery bank while maintaining the same voltage level. When batteries are connected in parallel, the positive terminal of a battery is connected to that of the next, and the same goes for the negative terminals.
This arrangement can be thought of as a team of rowers in a boat, each rowing at the same pace (voltage), but the more rowers there are, the longer they can keep rowing (increased capacity).
100 Ah + 100 Ah = 200 Ah (@12V)
For example, if two 12V batteries, each with a capacity of 100 Ah, are wired in parallel, the resulting configuration will remain at 12 volts, but the capacity will double to 200 Ah.
This means the device will operate at the same voltage but for a longer period, making the parallel configuration ideal for devices requiring extended operational time, like some power banks required for trolling motors, golf carts and larger RVs.
An additional advantage of the parallel configuration is its inherent redundancy. If one battery fails or is disconnected, the other batteries in the parallel connection can still provide power, albeit with a reduced total capacity.
Therefore, wiring batteries in parallel can be a way to enhance the durability and reliability of a device's power source.
As with battery banks with series connections, it is important to ensure that each battery in your battery system is of the same chemistry (all lithium batteries, for instance), preferably with the same brand and battery capacity and parallel connections require batteries of the same voltage.
Parallel battery banks that violate any of these principles will lead to performance issues over time.
Advantages of wiring batteries in parallel
There are several key advantages of wiring batteries in parallel:
- Increased Capacity: Wiring batteries in parallel increases battery amp hour capacity, allowing devices to run for a longer time at the same voltage.
- Redundancy: If one battery fails in a parallel configuration, the device can still operate, but with a reduced overall capacity. This provides a level of redundancy not present in a series configuration.
- Flexibility in Design: Parallel configurations offer flexibility in device design. Different arrangements can be created based on the device's form factor and capacity requirements.
- Cost Efficiency: It might be more cost-effective to wire multiple smaller-capacity batteries in parallel to achieve the desired capacity, rather than purchasing a single, larger-capacity battery.
- Balanced Charging: When correctly configured, all batteries in a parallel setup can be charged simultaneously from a single source, which can simplify the charging process.
- Less Voltage Safety Concerns: With voltage remaining the same across all batteries, there are generally fewer safety concerns related to high voltage.
- Versatility: A parallel configuration can be used to power a wide variety of devices that require extended operational times at a consistent voltage.
Disadvantages of wiring batteries in parallel
There are also several disadvantages of wiring batteries in parallel:
- Balancing Issues: The batteries in a parallel configuration need to be balanced correctly. If not, one battery could end up discharging into another, potentially causing damage or reducing the overall lifespan of the batteries.
- Uneven Discharge and Recharge: Despite being in parallel, batteries may not charge or discharge evenly due to variations in internal resistance, age, or capacity, which can affect overall performance.
- Complex Charging: A parallel setup might need a more complex charging system to ensure all batteries charge at the same rate, adding to the overall cost and complexity.
- Mismatched Batteries: As with series configurations, it's essential to use identical batteries (same type, capacity, charge level, brand, ideally from the same production batch) in a parallel configuration to avoid premature failure or decreased performance.
- Lower Voltage: A parallel configuration maintains the same voltage as a single battery. Therefore, it cannot be used to increase voltage for devices that require a higher voltage.
- Space Requirements: Depending on the number of batteries used, a parallel configuration could require more physical space, which might not be ideal for compact applications.
Wiring Batteries in Series-Parallel Connection
In certain applications, it might be necessary to combine the advantages of both series and parallel configurations to meet specific power requirements. This leads us to a third configuration known as series-parallel wiring.
This wiring method is typically only possible in applications where large amounts of power are required over long durations and in vehicles with a lot of space for the battery bank, such as large boats, Class A motorhomes and large travel trailers and fifth wheels.
Connecting batteries in a series-parallel connection is essentially a combination of series and parallel connections, where batteries are grouped into sets wired in series, and then these sets are connected in parallel.
This configuration allows for both a boost in system voltage and an increase in amp hour capacity, providing greater flexibility to meet a wider range of power requirements.
Consider a setup where two sets of 12-volt batteries are wired in series, with each set having a capacity of 200 Ah. Each set would have a total voltage of 24 volts, as per the series configuration rules.
Now, if these two sets are wired together in parallel, the capacity would double to 400 Ah, while the voltage would remain at 24 volts.
This effectively gives you the best of both worlds — the increased voltage of a series configuration and the increased capacity of a parallel setup.
In practical scenarios, you can see series-parallel configurations in electric vehicles, golf carts, or trolling motors. These applications often require a high voltage to function effectively and a high capacity to ensure a reasonable operational time between charges.
The series-parallel setup ideally meets these requirements by providing a balance between the two.
However, similar to the series and parallel configurations, it's crucial to ensure that the batteries used in a series-parallel setup are identical (same type, capacity, charge level, brand, ideally from the same production batch).
Additionally, the wiring must be done correctly, and a capable battery management system is often necessary to ensure all batteries charge and discharge evenly.
While the series-parallel configuration brings more complexity to the table, it also opens up a world of possibilities in terms of power provision. By understanding the principles behind this setup, users can optimize the performance of their devices or systems, and you can design more efficient and powerful energy solutions.
How to Wire Batteries in Series
If you decide that it is best to wire batteries in series, then you will want to follow the instructions below.
Remember: Always take precautions when working with electrical components. Wear protective gear if necessary, and always follow manufacturer guidelines. If you're unsure, it's better to consult with a professional.
- Two or more identical batteries
- Connecting wire(s), lugs and heat-shrink wrap
- Tools for connecting wires (like wire strippers, crimpers, and soldering iron if necessary)
- Identify Your Batteries: Ensure all the batteries are identical — same type, brand, capacity, and state of charge. Using mismatched batteries can lead to underperformance or damage.
- Position Your Batteries: Arrange your batteries so the positive terminal of the first battery is near the negative terminal of the second battery. This arrangement will make the connections easier.
- Connect the Batteries: Take a connecting wire. Attach one end of the wire to the positive terminal of the first battery. Connect the other end of this wire to the negative terminal of the second battery. If you're using more than two batteries, repeat this process. Always connect the positive terminal of one battery to the negative terminal of the next.
- Check Your Connections: Make sure all the connections are secure. Loose connections can cause your battery setup to work inefficiently and can even be a safety hazard.
- Test Your Setup: Once everything is connected, you can measure the voltage across the whole setup using a multimeter. The voltage should equal the sum of the voltages of the individual batteries. If your measurements don't match up, double-check your connections.
- Complete the Circuit: Connect your series battery setup to your device or battery system. The positive terminal of the first battery in your series will be the positive connection to your device, and the negative terminal of the last battery in your series will be the negative connection to your device.
All of our lithium batteries are great for combining in either parallel or series.
How to wire batteries in Parallel
Wiring batteries in parallel is a similar process to that of wiring batteries in series. The most significant difference is in how you connect the two batteries.
Unlike batteries in series, wiring parallel batteries require that you connect the negative terminal of the first battery to the negative terminal of the second battery. And likewise, you connect the positive terminal of one battery to the positive terminal of the second battery.
Thus you will want to orient your batteries such that the positive terminal of the first battery is near the positive terminal of the second battery, and the same for the negative terminal.
Apply the same principles if adding a third battery.
Note that when connecting your parallel battery bank to your power distribution panel or devices you will want to take the positive lead from one battery and the negative lead from the other (or furthest battery away in the parallel circuit) to improve efficiencies in your system.
Charging Batteries in Series Vs. Parallel
Charging batteries, whether in series or parallel, requires a good understanding of the configuration and its unique characteristics. Both arrangements come with distinct advantages and challenges, especially when it comes to charging.
When batteries are wired in series, the total voltage increases while the capacity (Ah) remains the same. This higher voltage necessitates a charger with an output voltage equal to the combined voltage of the batteries.
However, a critical consideration when charging batteries in series is the potential for unequal charging. This can occur due to small differences in each battery's capacity, internal resistance, or self-discharge rates.
Over time, these differences may lead to some batteries being overcharged, while others may be undercharged, leading to reduced battery performance and lifespan.
On the other hand, when batteries are wired in parallel, the capacity increases while the voltage remains constant. This configuration requires a charger with an output voltage equal to that of the individual batteries.
A significant advantage of charging batteries in parallel is that all batteries tend to receive an equal charge, as long as the batteries are matched and the connections are properly made.
However, parallel charging can be more complex if one battery becomes discharged more than the others. The more charged batteries can discharge into the less charged battery, leading to potential imbalance and inefficiencies.
Regardless of whether batteries are wired in series or parallel, it is crucial to use a compatible and high-quality charger. A battery management system (BMS) is often employed to monitor and control the charging process, ensuring each battery charges safely and evenly.
A BMS can help mitigate the challenges associated with both series and parallel configurations, contributing to improved battery performance and longevity. All of our lithium batteries have built-in BMS that can handle both series and parallel connections effectively.
The Bottom Line
The decision to wire batteries in series vs parallel largely depends on your specific power requirements. Wiring batteries in series increases the total voltage, which is suitable for devices needing a higher operating voltage, while wiring in parallel increases battery capacity in amp hours, allowing for longer operation time at the same voltage level.
Both configurations have their unique advantages and potential challenges, particularly when it comes to charging and maintaining balance.
Remember that mismatched batteries can lead to imbalances and inefficiencies, which can affect performance and lifespan, whether you're wiring in series or parallel. Also, when dealing with battery configurations, safety should always be a top priority.
If not using our lithium batteries, employing a battery management system can help monitor and maintain optimal performance.
Understanding the fundamentals of series and parallel battery configurations will empower you to make the right choice for your specific power needs and ensure you maximize the potential of your battery bank.
Frequently Asked Questions
How many batteries can I connect in series or parallel?
The number of batteries you can connect in series or parallel largely depends on the specific requirements of your device or system, as well as the batteries' specifications. However, in theory, there is no hard limit to the number of batteries you can connect in either configuration.
You can continue adding batteries to increase the total voltage (in series) or total capacity (in parallel) until you meet your system's requirements.
However, while there isn't a theoretical limit, real-world applications often require a balance between the number of batteries and the manageability of the setup.
Do Batteries Last Longer When Wired in Series or Parallel
The longevity of batteries wired in series vs parallel is contingent upon the definition of 'lasting longer'. If 'lasting longer' refers to the time the batteries can power a device before needing a recharge (i.e., the capacity), then batteries wired in parallel would last longer.
This is because wiring batteries in parallel increases the total capacity of the battery setup, allowing the device to run for a more extended period at the same voltage. Therefore, if you need a device to operate longer between charges, a parallel configuration would be more appropriate.
However, if 'lasting longer' refers to the overall lifespan of the batteries, it's more complicated. The lifespan of batteries in both series and parallel setups can be affected by numerous factors, including charge and discharge rates, balance of charging, quality of the batteries, and more.
In a series configuration, the failure of one battery affects the entire chain, while in a parallel setup, a failing battery can be bypassed, but it can cause balance issues that can affect the overall lifespan. Hence, proper management and maintenance are crucial in both configurations to maximize battery lifespan.
How Do I charge Batteries in series vs parallel
Charging batteries wired in series versus parallel requires understanding the unique characteristics of each configuration. For series configurations, the charger's output voltage needs to match the combined voltage of all batteries.
For instance, if you have four 12V batteries wired in series, resulting in a 48V configuration, you'd need a 48V charger.
It's important to note that charging batteries in series can sometimes lead to imbalance, with some batteries possibly overcharging while others may undercharge. Therefore, using a balanced charger or a battery management system (BMS) can be beneficial for equal charging and enhancing battery life.
Conversely, when charging batteries wired in parallel, the output voltage of the charger should equal the voltage of the individual batteries, as the total voltage in a parallel configuration remains constant.
For example, if you have four 12V batteries wired in parallel, you'd use a 12V charger.
An advantage of parallel charging is that all batteries tend to receive an equal charge. However, regular monitoring and employing a BMS can be beneficial for parallel configurations as well.
Can I connect 2 different size batteries in series or parallel?
Technically, it is possible to connect two different size batteries in series or parallel. However, it's generally not recommended, as it could lead to poor performance and potentially damage the batteries.
When you connect batteries in series or parallel, they should ideally be the same type, brand, model, capacity and state of charge. Mismatched batteries can cause imbalances in charging and discharging, reducing efficiency and battery life.
For example, if you connect two batteries of different capacities in series, the voltage across each battery will be the same when charging or discharging, which can lead to overcharging the smaller capacity battery and undercharging the larger capacity one.
Similarly, if you connect different capacity batteries in parallel, the higher capacity battery can end up discharging into the lower capacity battery, which can cause damage or inefficiency. Therefore, for best results and safety, it's always recommended to use matched batteries when connecting them in series or parallel.
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