A330 battery check

[subria023]

Hi all,

Please go easy on me ! I have some questions regarding the battery check during A330 preliminary cockpit preparation.

1. When we check the battery above 25.5 V, after the check, the selector should remain on APU position to minimize discharge of BAT 1 and 2. What exactly does this mean? How does BAT 1 or 2 get discharged?

2. For the APU start, if one of the batteries is lower than 23.5V, there is a risk of aborted APU start. In my understanding, APU has its own dedicated battery in order to start. Why do BAT 1 or 2 voltages have effect on APU start?

thank you,

subria023

[ahramin]

Good questions.

1. The voltmeter itself uses current. If you leave the voltmeter on Bat 1 or 2 for long enough with the battery switch off it will discharge the battery. I believe the same thing can happen to the APU but it is preferable to discharge the APU battery over the main ship batteries.

2. I don't know what the main batteries have to do with the APU start except that in EMER ELEC CONFIG the APU ECB is gets power from the DC ESS BUS during APU start.

Just remember that the electrical system diagrams in the manuals are abstract simplifications of the actual electrical system. Just because a relationship isn't shown doesn't mean it isn't there.

[subria023]

Thank you very much ! That makes more sense now.

[spannersatcx]

To prevent excessive drain when on the ground the Batteries disconnect if voltage is < 23 V for 16 sec. So leaving them switched on should not flatten the BATT's. Main BATT's have not connection to the APU as far as I am aware.

If both Batteries are AUTO, then the Batteries will supply:
1. AC ESS BUS
2. AC ESS GND
3. AC LAND RECOVERY BUS
NOTE: AC LAND RECOVERY BUS ignores the position of the Land Recovery Switch.

NOT Supplied:
1. AC ESS SHED
2. DC ESS SHED
3. SHED LAND RECOVERY

[rick.shaw]

AHRAMIN

Your point number two correct and important.

For example, if your APU TR is u/s(MEL'able), then your APU battery is on it's own in starting the APU on the ground(e.g taxiing in). You'll get one, maybe two, start cycles out of a charged up APU battery in this case, before requiring a charge cycle for the APU battery. A charge cycle, in the case of APU TR fault, I think will not be possible without power through the APU TR. Sometimes a reset of the TR allows this - until it fails again. I'm happy to be corrected on this though.

In the air only, the DC ESS will allow you to start the APU; regardless of the APU battery state(emerg elec config).