Modular battery systems face cell compatibility risks

Modular home battery systems face potential compatibility issues that may limit their long-term expandability. While marketed as stackable units that allow users to add capacity over time, changes in manufacturer supply chains can create technical mismatches.

Many systems, such as Sungrow’s SBR and SBH series, connect modules in series, requiring all cells to share consistent charge states, ages, and chemical batches. Because manufacturers often qualify multiple cell suppliers to meet demand, newer modules may not be compatible with older ones in the same stack. In one documented case, adding new modules to a 25.6kWh stack caused the usable capacity to drop to approximately 13kWh because the new cells failed to balance with the existing ones.