In an RV solar system, it is generally not recommended to combine different types or sizes of batteries, but it depends on the specific situation. Here's why:
1. Different Battery Types (Lead-Acid vs. Lithium vs. AGM)
- Voltage Mismatch: Different types of batteries (like lead-acid, AGM, and lithium-ion) have different charge/discharge characteristics, and their voltage profiles might not match. For instance, lithium batteries usually have a higher voltage than lead-acid, and mixing them could lead to overcharging or undercharging.
- Charging Systems: Each battery type often requires a specific charging profile. Using mismatched batteries could cause issues with your solar charge controller, which may be optimized for only one type of battery.
2. Different Battery Sizes or Capacities
- Uneven Charging: If you combine batteries of different capacities, the larger batteries may charge or discharge more efficiently than the smaller ones, causing an imbalance. This can reduce the lifespan of the smaller batteries and cause them to overheat or degrade faster.
- Imbalanced Discharge: If you have batteries of different states of charge, they might not discharge evenly. This can also damage one or more of the batteries over time.
3. Battery Age and Condition
- Batteries that are of different ages or in different conditions can also lead to performance issues. Older batteries may not hold a charge as well as newer ones, leading to inconsistent charging and discharging cycles.
Best Practice
If you're looking to expand your RV solar system, it's usually best to use batteries of the same type, size, and age to ensure compatibility and efficient performance. If you need to add new batteries, try to match the existing ones as closely as possible.
If you really need to mix different batteries (e.g., combining lead-acid and lithium), make sure your charge controller is compatible with both types and capable of managing each type’s unique charging requirements. You might also need a battery management system (BMS) to help manage the different characteristics safely.
