How to determine the matching battery capacity based on the rated power of the

Take 48V Lithium Iron Phosphate Battery as example.

Assumptions: DOD=0.8, inverter efficiency=0.92, overall efficiency factor≈0.7

1. Two mandatory requirements (both must be satisfied)
① Inverter determines minimum discharge current
Full-load DC current:I= Rated Power（kW）× 1000/(48 × 0.92)
3kW ≈ 68A｜5kW ≈ 113A｜6kW ≈ 136A
Maximum continuous discharge current of battery ≥ above value
> Max discharge current = Battery Capacity(Ah) × Discharge Rate (C)
② Power consumption determines battery capacity
Quick estimation: Required Ah ≈ Daily energy consumption(kWh) × 30
- Off-grid system: Increase result by 20%~40% for bad weather reserve
- Backup power for grid outage: Ah ≈ Inverter kW × Backup Hours × 30

2. Matching reference for standard 0.5C energy storage batteries
3kW inverter → Min. 48V150Ah, recommended 48V200Ah
5kW inverter → Min. 48V230Ah, recommended 48V250Ah
6kW inverter → Min. 48V300Ah, or adopt 0.6C+ high-rate batteries

3. Key pitfalls to avoid
（1）. Ignoring discharge rate while only checking capacity leads to power derating or shutdown under heavy load
（2）. Limit DOD within 0.8 for 48V LFP batteries; avoid deep discharge
（3）. Use thicker cables for high-current scenarios to reduce voltage drop