When sourcing a 5kW lithium battery, prioritize LiFePO4 (Lithium Iron Phosphate) chemistry due to its superior thermal stability and safety. Key specs include Cycle Life (look for ≥6,000 cycles at 80% DoD), Maximum Continuous Discharge Current (typically 100A for a 48V/51.2V system), and BMS (Battery Management System) integration which protects against overcharge, deep discharge, and short circuits. Ensure the battery supports RS485/CAN communication protocols to sync seamlessly with your specific inverter brand.