About the BESS Cable Route

BESS cable routing plans the DC interconnection cables between battery racks and the PCS, and the AC cables from the PCS to the step-up transformer — optimising cable lengths for minimum resistive loss, ensuring adequate separation, and meeting fire-rating requirements for battery enclosures.

How to calculate it

1. 1DC cables (battery rack to PCS): high-current, low-voltage runs. Keep as short as possible — typically < 10 m inside the container. Use flexible copper cables rated for the maximum DC string voltage and current.
2. 2AC cables (PCS to transformer): sized for the PCS rated AC current. Voltage drop limit: 0.5% maximum for the PCS-to-transformer run.
3. 3Cable sizing: use the same voltage drop formula as solar DC cables (ΔV = 2 × I × L × ρ ÷ A for DC; ΔV = √3 × I × L × ρ ÷ A for 3-phase AC).
4. 4Fire rating: cables inside BESS enclosures must be FRLS (Flame Retardant Low Smoke) or XLPE rated; LSZH (Low Smoke Zero Halogen) required in confined spaces per IEC 60332.
5. 5Segregation: DC battery cables must be segregated from AC PCS output cables — separate conduit or tray with physical divider.

Worked example

A 500 kW PCS at 400 V, 3-phase, PF 0.98. AC output current = 500,000 ÷ (√3 × 400 × 0.98) = 736 A. Cable run to transformer: 8 m. Voltage drop at 0.5% limit = 0.005 × 400 = 2 V. Required cable area = √3 × 736 × 8 × 0.0175 ÷ 2 = 89 mm² → use 95 mm² XLPE FRLS aluminium cable (3 parallel runs of 95 mm²).

What you can calculate

• Cable length m
• DC tray route
• AC feeder
• BOQ estimate

Frequently asked questions