MAIN BATTERY DISCH
π Sources: QRH 6.6 (R53), FCOM 6.30.1
1. QRH Reference & Condition
- QRH Section: 6.6
- EICAS Level: Advisory
- Condition: One of these occurs:
- The main battery is discharging
- The hot battery bus is not energized
CAUTION
The main battery can power the standby system for a minimum of 5 minutes. (QRH 6.6, FCOM 6.20.13)
2. Non-Normal Checklist
This is a condition awareness checklist β no specific crew reset actions.
The crew must assess the cause of battery discharge:
- Is the main battery charger receiving AC power? (ground service bus powered?)
- Are additional loads drawing battery power?
- Has the hot battery bus lost its normal power source?
3. System Explanation
The main battery is the last line of defense for standby power. It directly powers: (FCOM 6.20.13)
- Hot battery bus
- Battery bus
- Captainβs flight instrument bus (via C1 TRU when on standby)
- L and C flight control PSAs
- Standby inverter (β AC standby bus)
If discharging, battery life is limited to minimum 5 minutes. This is the time available to:
- Deploy RAT (auto-deploys if both transfer busses lost)
- Restore normal AC power (APU start, generator reset)
Battery Status on Synoptic Display
| Display | Meaning |
|---|---|
| DISCH (amber) | Battery is discharging (supplying power) |
| CHG (green) | Battery is charging normally |
| VOLTS / AMPS | Battery voltage and current |
4. Cross-References
- Electrical System β Standby power architecture, battery description
- RAM Air Turbine (RAT) β Emergency power when battery depleting
- ELEC AC BUS L, R β AC bus unpowered (may cause battery discharge)
- ELEC BACKUP SYS β Backup system failure