Mixing old and new deep cycle batteries

The age-old question (pun intended)!

Mixing old and new deep cycle batteries can be a bit tricky, as it's essential to ensure compatibility and optimal performance. Here's a breakdown of the considerations:

Why mixing old and new batteries might not be ideal:

  1. Different capacities: Old batteries might have lower capacities than new ones, which can lead to uneven charging and discharging.
  2. Differing internal resistances: Old batteries may have higher internal resistances, which can affect the overall performance and lifespan of the new batteries.
  3. Incompatible chemistries: If the old batteries are lead-acid and the new ones are AGM (Absorbed Glass Mat) or gel, there might be compatibility issues.
  4. Different maintenance requirements: Old batteries might require more frequent maintenance, such as equalization, which can be challenging with new batteries.

When mixing old and new batteries might be acceptable:

  1. Similar capacities: If the old and new batteries have similar capacities, it's more likely that they can be mixed without significant issues.
  2. Same chemistry: If both batteries are lead-acid or AGM/gel, the compatibility risk is lower.
  3. Minimal difference in internal resistance: If the internal resistances of the old and new batteries are similar, it's less likely to cause significant performance issues.

Best practices for mixing old and new deep cycle batteries:

  1. Check the battery specifications: Verify the capacities, chemistries, and internal resistances of both old and new batteries.
  2. Monitor performance: Keep a close eye on the performance of the mixed batteries, as uneven charging and discharging can occur.
  3. Maintain the batteries properly: Regularly check and maintain the batteries according to the manufacturer's recommendations.
  4. Consider upgrading the entire system: If the old batteries are significantly outdated or have high internal resistances, it might be more cost-effective to replace the entire system with new batteries.

In summary, while mixing old and new deep cycle batteries is possible, it's essential to consider the potential compatibility issues and take steps to ensure optimal performance. If you're unsure, it's always best to consult with a professional or replace the entire system with new batteries.