Multiple batteries in the same bank – what needs to match?

All guides · Batteries and charging

Series and parallel yield different results

The example explains the principle using nominal rated values. The specific battery model must explicitly permit the desired connection. A lithium battery approved for parallel connection is not necessarily approved for series connection.

Check this before an expansion

• Model and chemistry: Is the combination permitted by the manufacturer?
• Age and condition: Is the existing bank suitable for expansion, or should it be evaluated first?
• Quantity: What is the permitted number of batteries or strings?
• Preparation: What charging and voltage balancing does the manual require before interconnection?
• Protection: How should each branch, the main connection, and the disconnection be implemented?
• Space: Are the mounting, terminal protection, temperature, and service access adequate?

Connections affect current distribution

In its installation guide, Victron emphasizes that the resistance in connections affects current distribution between parallel batteries. A planned setup with balanced current paths is therefore important. Random extra cables to the nearest battery can result in a different distribution than expected.

I would have a complete schematic drawn up including busbars, fuses, switches, and monitoring. This is especially relevant when the bank is also intended to supply a larger inverter.

More Ah also requires more charging

Write down the purpose of the expansion: longer time at anchor, higher peak load, or both. More capacity does not automatically provide a stronger charger or more hours of sunlight. Use your daily consumption and available charging time to determine if the expansion solves the right problem.