Many users wonder whether lithium batteries with different capacities can be connected together. For example, can a 100Ah battery be connected to a 200Ah battery within the same energy storage system?

Technically, it may be possible under certain conditions, but it is generally not recommended for long-term operation.

Lithium batteries perform best when they share similar specifications, including capacity, voltage, age, and internal resistance. When batteries with different capacities are connected together, charging and discharging behavior can become uneven.

The larger battery may supply more energy, while the smaller battery reaches its charging or discharging limits sooner. Over time, this imbalance can affect system efficiency and increase stress on the battery management system (BMS).

Potential issues include:

• Uneven charging and discharging

• Reduced system efficiency

• Increased balancing requirements

• Possible BMS protection events

For users planning to expand an existing energy storage system, the safest approach is to use batteries with matching specifications from the same manufacturer whenever possible.

A properly matched battery bank improves reliability, simplifies maintenance, and helps maximize the overall lifespan of the system.