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1505

Generac Standby Generator

Severity: Moderate

Source: OnlyErrorCodes.com — Every error code. One place.

Generac Generator 1505 — Battery Charger Warning

What Does This Error Mean?

Alarm 1505 on a Generac standby generator means the battery charger has no AC input — the generator's battery cannot be maintained from utility power. The generator still runs from battery start, but the battery will eventually go flat without charging. Restore AC power to the charger to clear 1505.

Affected Models

  • Generac Guardian 22kW
  • Generac Guardian 26kW
  • Generac PowerPact 7.5kW
  • Generac EcoGen 15kW
  • Generac Protector RG022

Common Causes

  • Tripped breaker on the charger circuit at the home electrical panel
  • Charger AC wire disconnected at the generator junction box
  • Failed battery charger module
  • Power outage at the time the alarm set (clears after power returns)
  • Loose connection at the charger AC input terminals

How to Fix It

  1. Check the charger breaker.

    Find the breaker at your home's electrical panel that supplies the generator's battery charger (typically a 15A breaker labelled GEN BATTERY or GENERATOR). If tripped, reset to ON.

  2. Confirm utility power is present.

    If the home is currently in a power outage, alarm 1505 may be set because there is no AC anywhere. The alarm clears when utility power returns. Wait for the outage to end before troubleshooting.

  3. Inspect the charger AC wiring at the generator.

    Open the generator's electrical compartment (with the unit OFF and battery disconnected for safety). Check the charger AC input terminals are firmly connected. Loose connections cause 1505 even when the breaker is on.

  4. Test the charger output.

    With AC restored and breaker on, the charger should output 13.5–14.4V to the battery. Use a multimeter on the battery terminals (engine off, charger on). Voltage outside this range with breaker on means the charger has failed.

  5. Replace the charger if failed.

    Generac battery chargers cost USD 80–180. Replacement is moderate DIY for those comfortable with mains wiring inside the generator. Otherwise book a Generac dealer — typical cost USD 250–400 fitted.

Frequently Asked Questions

How long can my Generac run on battery without 1505 being fixed?

Standby generators only run their battery during the start cycle (a few seconds per start) and a few hours per month for exercise. A healthy battery can last 4–8 weeks without charging before becoming too weak to crank. Fix 1505 within a couple of weeks to be safe.

Why did 1505 appear during a power outage?

Alarm 1505 is set whenever the charger has no AC input — including utility outages. The generator is correctly running from battery and powering your home. The alarm clears automatically when utility power returns.