Energy Storage & Batteries

Battery C-Rate & Motor Surge Power Matching

Core Question: How do you determine if a home battery can start a central air conditioning compressor or well pump during a grid blackout?

Governing Physics Formula / Design Rule
Continuous_Power_kW = Capacity_kWh * Continuous_C_Rate | LRA_Surge_kVA = Inrush_Current * Volts

Executive Technical Summary

A 10 kWh battery with a 0.5C rating can only deliver 5 kW continuous power. Induction motors (HVAC, well pumps, heat pumps) require Locked Rotor Amps (LRA) surge power 3 to 6 times higher than running watts.

Detailed First-Principles Explanation

For example, a 3-ton central A/C compressor drawing 3.5 kW running power can draw an instantaneous starting surge of 18 kW (75A LRA for 150ms). If your battery and hybrid inverter peak surge rating is under 15 kVA, the battery protection BMS will instantly trip on over-current.

Critical Field Pitfall & Safety Warning

Never assume a 15 kWh battery can power a whole house; always check the instantaneous peak kW surge rating and install a soft-starter on central A/C units.

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