Can I Combine 36V and 24V Batteries in Series?

When considering the combination of two battery packs with different voltages, such as a 36V and a 24V, you might wonder if it's advisable to connect them in series. This question is often raised in the context of building a higher-voltage battery pack, particularly for applications like electric vehicles or stationary power storage solutions. The answer is yes, but with considerations to ensure safety and functionality.

Understanding Voltage Addition in Series

The principle of adding voltages in series is a fundamental concept in electrical engineering. When two battery packs are connected in series, their voltages add together to form a higher overall voltage. In your case, if you connect a 36V battery in series with a 24V battery, you will achieve a nominal 60V system. This is a straightforward process adhered to by both novice and experienced users.

Ensuring Capacity and State of Charge Balance

While the basic principle of adding voltages holds true, there are important factors to consider to ensure the longevity and performance of your battery pack. One of the key points to address is the capacity and state of charge (SoC) of the batteries. It is crucial that the individual cell capacities and current capacities of the two batteries are as close as possible. If these capacities differ significantly, your system may not operate efficiently, and you might not achieve the desired voltage and current output.

State of Charge Considerations

Maintaining a balanced state of charge is crucial. Before connecting the batteries to a charger, make sure both batteries have approximately the same state of charge. If the SoC is not balanced, you risk creating an imbalance in the overall system, which could lead to issues such as uneven discharge rates, reduced performance, and potentially even damage to the batteries. This is especially important when working with electric vehicle batteries or any other system where consistent performance is critical.

Practical Application and Safety Measures

When combining batteries in series, consider the following practical steps:

Select compatible batteries: Choose batteries that have similar capacities and perform well within the same temperature range. Check for matching current ratings: Ensure that both batteries can handle the same current to avoid overloading the weaker battery. Balance state of charge: Equalize the batteries' SoC before performing the connection. Monitor the system: Continuously monitor the system for any signs of imbalance or overheating. Use protective measures: Incorporate fuses and BMS (Battery Management Systems) to protect against overloads and ensure safety.

By carefully adhering to these guidelines, you can successfully combine a 36V and a 24V battery pack to achieve a 60V system. This method not only provides the necessary voltage for your application but also ensures that your batteries operate efficiently and safely.

Conclusion

The combination of a 36V and 24V battery pack to achieve a 60V system is a valid approach, provided you pay attention to capacity and state of charge balance. With proper planning and safety measures in place, you can achieve the desired voltage and performance in your battery pack while minimizing potential risks.

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