Yes, lead-acid batteries of different capacities can be connected in series, but there are important considerations and potential issues to be aware of.
- Imbalance in Charging and Discharging:
- When batteries of different capacities are connected in series, the battery with the lowest capacity will reach its full charge or discharge state first. This can lead to overcharging or over-discharging of the lower capacity battery, which can damage it and reduce its lifespan.
- Voltage Differences:
- In a series configuration, the total voltage is the sum of the voltages of all batteries. Batteries of different capacities might not have the same voltage characteristics under load, which can create imbalance issues.
- State of Charge Monitoring:
- It becomes more challenging to monitor and manage the state of charge (SoC) and state of health (SoH) of each individual battery. Without proper monitoring, some batteries might be stressed more than others, leading to premature failure.
- Equalization Needs:
- Regular equalization charges may be required to balance the state of charge among the batteries. This process can help mitigate some of the imbalances but cannot entirely eliminate the inherent issues of connecting different capacities in series.
- Performance and Safety:
- The overall performance and safety of the battery bank might be compromised. Imbalances can lead to reduced efficiency and potential safety hazards, such as overheating or thermal runaway.
To mitigate these issues, it’s generally recommended to:
- Use batteries of the same capacity, age, and type in a series configuration.
- Implement a battery management system (BMS) to monitor and balance the state of charge of each battery.
- Regularly perform maintenance and equalization charging to ensure all batteries are balanced.
While it’s technically possible to connect lead-acid batteries of different capacities in series, it’s not ideal and should be done with caution and proper management systems in place.
