Can we connect lead acid and lifepo4 batteries in parallel

Can We Connect Lead Acid and LiFePO4 Batteries in Parallel? Understanding the Risks and Strategies

The Challenges of Mixing Battery Types

1. Voltage Differences:
   1. Nominal Voltage Discrepancy: Lead acid batteries typically have a nominal voltage of about 2.1 volts per cell (12.6 volts for a 6-cell battery when fully charged), whereas LiFePO4 batteries usually have a nominal voltage of 3.2 volts per cell (about 12.8 volts for a 4-cell configuration). This slight difference can create imbalance during charging and discharging.
2. Charging Characteristics:
   1. Charge Voltage: Lead acid and LiFePO4 batteries require different charging voltages, which complicates the charging process when connected in parallel.
   2. Charging Curve: LiFePO4 batteries charge differently than lead acid, often requiring a constant current/constant voltage (CC/CV) charge method which doesn’t align with the typical constant voltage charging of lead acid batteries.
3. Discharge Rates and Capacity:
   1. Different Discharge Profiles: The batteries discharge at different rates. When connected in parallel, this can lead to one type discharging faster than the other, potentially leading to ‘voltage dragging’ or over-discharging of the slower-discharging battery.
   2. Capacity Variation: If the batteries have different capacities, it can further complicate the energy balance between them.
4. Age and Condition:
   1. Battery Health: Mixing old and new batteries, or batteries in different states of health, can lead to reduced performance and lifespan.

Risks Involved

• Safety Risks: Imbalances in charging and discharging can lead to safety issues such as overheating, which may result in battery damage or failure.
• Reduced Efficiency: The overall system efficiency may be compromised due to the energy losses from managing imbalances.
• Shortened Lifespan: Each battery type could degrade faster due to stress from operating outside optimal conditions.

Best Practices and Alternatives

• Separate Battery Systems: Instead of connecting them in parallel, maintaining separate systems for each battery type is usually safer and more efficient.
• Use of a Battery Management System (BMS): For setups that must mix battery types, using a sophisticated BMS can help manage the charging and discharging processes to minimize risks.

How Himax Electronics Can Help

• Custom BMS Solutions: Himax designs BMS solutions that can handle complex scenarios, including mixed-battery setups, ensuring each battery operates within its safe parameters.
• Expert Consultation: Himax offers expertise in energy storage solutions, helping clients design systems that are both safe and efficient, tailored to their specific needs.
• Safety Enhancements: By implementing Himax’s cutting-edge technology, users can mitigate the risks associated with connecting different battery types in parallel.

Conclusion