Path-Q Solar
How should a generator be sized if it will recharge a battery rather than power loads directly?
Answer
Size the generator for the battery charger's required input power plus any loads that must run while charging, while staying within the generator's continuous and surge ratings. The generator does not necessarily need to match the home's maximum load, but it must be compatible with the charger and controls.
Key points
- The charger input rating, charging efficiency, and desired recharge time determine the generator's charging requirement.
- Any simultaneous backup loads must be added to the charging load.
- Generator continuous capacity matters more than a short-term peak for sustained charging.
- The battery system may limit generator operation, charging current, or generator start and stop commands.
What it depends on
- Battery usable capacity and target recharge time
- Charger input power, efficiency, and power factor
- Loads operating during generator charging
- Generator continuous and surge ratings and control compatibility
Risks and trade-offs
- An oversized generator may operate inefficiently at light load.
- An undersized generator may overload, trip, or fail to charge reliably.
- Fuel availability, noise, ventilation, maintenance, and emissions affect practical backup duration.
Information you may need
- Battery and charger specifications
- Required recharge time and minimum reserve
- Loads that operate during charging
- Generator operating ratings and approved integration method
Your next step
What to do next
Obtain the battery inverter/charger's maximum input and control requirements, then have the generator and battery integrator calculate continuous and surge capacity together.
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SQ01981