SMA Sunny Island SI4.4M-12 (used, well looked after, excellent condition) — A 4.4 kW off-grid/battery inverter from SMA that manages energy between batteries and AC loads for off-grid systems, self-consumption setups, or battery backup. It runs on 48 V battery input and outputs 230 V AC, supports both lead-acid and many lithium-ion batteries, and includes built-in communication (WLAN/LAN) for monitoring and control. This unit is rugged, reliable, and ideal for smaller off-grid or backup solar systems.