Batteries in Series vs Parallel: Which is Better for You?
To meet your power needs when you require more than one battery, there are two ways to set up your battery connection: a series connection or a parallel connection.
In a series connection, the positive end of a battery connects with the negative end of another battery. This positive-to-negative connection increases the total voltage but keeps the same current or capacity (amp hours).
In a parallel connection, the positive end of a battery connects to the positive end of another battery, while the negative ends connect to the negative ends. This increases the capacity or current but keeps the same voltage.
Choosing the optimal configuration will depend on your power needs and the system requirements.
Table of Content
Part 1. Wiring Batteries in Series
A series configuration links two or more batteries together to create a chain of positive-negative connections.
For example, three 12V batteries, each having a capacity of 200Ah can be connected to give: 12V + 12V + 12V = 36V
However, the total capacity or current will remain at 200Ah. This means the current of 200Ah is now shared between three batteries rather than just one.
If you want to power a 12V device with 2V batteries using a series setup, you will need six 2V batteries: (2V x 6 = 12V).
1.1 Benefits of Batteries in Series
- Higher voltage for powering high-wattage devices: You can easily increase your voltage for different devices.
- Potentially longer lifespan due to lower current: The current is now being split amongst the total number of batteries, reducing the strain on each battery.
- Simpler charging process: Since the same current is flowing through all the batteries, you'll be getting a uniform charging process.
1.2 Drawbacks of Batteries in Series
- Increased risk of imbalance between batteries: If one battery starts to degrade, it can create an imbalance between the batteries as one current flows throughout all of them. In other words, a series configuration is only as strong as its weakest battery.
- Requires a battery management system (BMS): A BMS helps monitor each battery. However, the system isn't cheap, and it adds to the costs of your battery setup.
1.3 Ideal Applications of Series Connections
Batteries in series work well where higher voltage is important. Here are some ideal applications:
- Electric Vehicles (EVs): Electric vehicles require large amounts of voltage to power their motors. By connecting battery cells in series, EV manufacturers can provide high voltages effectively.
- Laptops and Smartphones: Laptops and smartphones use series configurations to provide efficient high voltages and long usage times.
- Power Tools: Some power tools require high voltages when drilling or cutting. Series-connected batteries can ensure these high-performance tools operate effectively.
- Solar Power Systems: Solar panels often use series-connected batteries for their inverters. This setup allows efficient power conversion from solar energy to electricity.
1.4 How Many Batteries Can I Wire in Series?
The number of batteries you can wire in series will depend on the voltage limits of your system. For LiTime lithium batteries system, it's suggested not to over 48V.
Although there isn't any upper limit to how many batteries you can connect in series, especially if you are building a battery-powered device. You must take into account safety, voltage limits, and efficiency.
- Lithium-Ion Batteries: Laptops typically have four 3.6V Li-ion batteries in a series while electric vehicles can use 2000+ Li-ion batteries in a pack.
- Lead-Acid Batteries: A 12V car battery uses six 2V cells in series. In solar power systems, four 12V batteries are used in series to match the inverter's voltage requirements.
- Nickel-Metal Hydride (NiMH) Batteries: A power tool requiring 18V will need fifteen 1.2V NiMH batteries.
When wiring batteries in series, try to regularly balance the charge across all the batteries, which you can achieve with a battery management system (BMS).
A BMS will prevent overheating, overcharging, and over-discharging issues. Furthermore, use batteries of the same type, age, and capacity to avoid imbalances.
Part 2. Wiring Batteries in Parallel
A parallel configuration links batteries by connecting the positive terminals and the positive terminals.
For example, if you have three 2V AA batteries, each with 2000mAh, you will have a total of 6,000mAh. in this case, the capacity or current changes and the voltage stays the same.
2,000mAh + 2,000mAh + 2,000mAh = 6,000mAh
However, the voltage of 2V will stay the same.
Parallel-connected batteries work well when you need to run a constant voltage for a long time. The setup above will allow the device to run three times longer (due to an increased capacity) than if you used one battery.
Benefits of Wiring Batteries in Parallel
- Increased capacity for longer runtime: A higher capacity allows you to have longer runtimes for your devices without having to continuously recharge or replace your batteries.
- Better tolerance for battery imbalances: When batteries are connected in parallel, a weaker battery with a lower capacity won't affect the others.
- Easier to maintain: As it's not necessary to have perfectly matched batteries, a parallel configuration is easier to maintain.
Drawbacks of Wiring Batteries in Parallel
- Higher current, requiring thicker cables: Because parallel-connected batteries have a higher overall current, you will need thicker cables to handle the increased load efficiently. Thicker cables prevent overheating.
- More complex charging process: Charging parallel-connected batteries can be challenging as some batteries may overcharge while others may undercharge. The same goes for the discharge process. Some batteries may discharge faster than others.
Ideal Applications of Parallel Connections
Parallel configurations work well when extended runtimes are crucial. Here are some ideal applications:
- Portable Electronics: Portable electronics, such as radios and alarm clocks, need parallel setups as they offer small voltages but long usage times.
- Power Banks: Portable power banks use parallel-connected batteries to provide extended charging times to multiple devices.
- Electrical Panels: The wiring of your home uses a parallel configuration, supplying the home with one voltage. If one light or appliance goes off, the current still flows to the other appliances.
How Many Batteries Can I Wire in Parallel?
The number of batteries you can wire is limited based on the the system and the need for balanced charging. However, there are factors to consider, such as the amount of physical space you have and the design of the system you intend to power.
- Lead-Acid Batteries: Off-grid solar setups typically use a 12V system consisting of four 12V 100Ah batteries, providing a total current of 400Ah.
- Lithium-Ion Batteries: Connecting 3.7V cells in parallel can increase the battery of your laptop without changing the voltage.
- Nickel-Metal Hydride (NiMH) Batteries: NiMH batteries can be connected in parallel to power tools to provide longer usage times.
When using batteries in parallel, try to balance the charge/discharge cycle across all your batteries. This can extend the lifespan of your battery system.
Part 3. How to Choose the Right Configuration: Parallel vs Series Batteries
Choosing the right configuration for your batteries, whether series or parallel, will depend on a few factors.
1. Power Requirements
Determine how much voltage your device will need and how many batteries it will take to meet that requirement. In addition, assess how much current your device will draw.
If your device needs a high current, a parallel configuration may be more suitable. In some cases, you may need a series-parallel configuration to meet both your current and voltage requirements.
2. Desired Runtime
If you need long run times, consider a parallel setup. In a solar power storage system, long run times can ensure that your system provides power when there is no sunlight. If your device doesn't need to run for long periods, a series configuration may suffice.
3. Battery Time
Another factor to consider is the battery time. In a series configuration, the battery time will remain the same, but the battery pack will have a higher voltage. In a parallel configuration, the battery time increases. This means your device can run longer before needing to recharge.
4. Available Space and Weight Limitations
In a series configuration, the batteries can be stacked on top of each other, reducing the amount of space needed. A parallel configuration requires the batteries to be laid out side by side. As a result, this setup requires more space.
In both cases, adding more batteries means adding more weight. If you have weight limitations, you may have to think about how many batteries you will need in total to meet your voltage and current requirements.
5. Safety Concerns
Higher currents in parallel configurations can quickly lead to overheating. If this is a concern, use thicker cables and provide proper insulation. You can also implement a BMS to monitor your charge/discharge cycles for both a series and parallel setup.
6. Maintenance
Parallel configurations require less maintenance as one weak battery won't affect the rest of the system. Series configurations need more monitoring as the system is only as good as its weakest battery.
7. Budget
Series configurations tend to be simpler as less wiring is required. If budget is a concern, then a series setup may be the best choice. Parallel configurations are more expensive upfront, but they require less maintenance and can provide longer runtimes.
Part 4. The Final Verdict: Parallel vs Series Batteries
The final configuration you choose for your battery connection will depend on your scenario.
The series configuration is best for:
- High-voltage systems
- High-voltage systems where you shouldn't increase the current
The benefits of this setup are that you'll have an efficient, simple, and safe system. The drawback is that this configuration isn't always as durable. A failure in one battery affects the entire setup.
The parallel configuration is best for:
- Long runtimes
- Increased capacity while maintaining the same voltage
The benefits of this setup are a durable system that has better tolerance and the ability to provide longer than normal runtimes.
Safety issues are a drawback as the system can easily overheat. Another drawback is the complexity of the system. You will need thicker cables and a Battery Management System (BMS).
Both configurations have their strengths, so your best choice depends on whether you choose to prioritize voltage (series configuration) or current (parallel configuration).
Can You Wire Batteries in Series and Parallel Simultaneously?
Yes, it's possible to wire batteries in series and parallel simultaneously. This is often done when you need to meet specific capacity and voltage requirements. The combined configuration is called a series-parallel connection.
For example, you can connect three 12V 100Ah batteries in series and connect that series configuration to three 12V 100Ah batteries in parallel.
Series Pack + Parallel Pack = Series-Parallel Connection
Precautions to notice when wiring batteries:
- Identical batteries with the same battery capacity (Ah) and BMS (A);
- Batteries are from the same brand ( as different lithium batteries from different brands have their special BMS)
- Purchased in near time (within one month)
FAQs on Series vs Parallel Connections
1. Do batteries last longer in series or parallel?
The lifespan of batteries, whether connected in series or parallel, largely depends on the type of battery, the quality of the batteries, the load they are powering, and how well they are maintained.
In many cases, a combination of series and parallel connections is used to achieve the desired voltage and capacity for a given application. The key to maximizing battery lifespan in either configuration is proper management, maintenance, and matching of batteries in terms of capacity and charge state.
What's the difference between batteries in series vs. parallel configurations?
Batteries in series connect the positive end of a battery to the negative end of another battery. This increases the total voltage and keeps the capacity the same. Batteries in parallel connect the positive end to a positive end and a negative end to a negative end. This keeps the voltage the same and increases the capacity.
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