Hello gents.The ETOPS Battery option has been bugging me for a while because I don't know why, or when the second battery was added.We don't have the additional battery on our planes, yet, our NG's are all 180min ETOPS certified, as per Boeing Document D044A007 "737-600/-700/-800/-900/-900ER ETOPS Configuration, Maintenance and Procedures".So my question is this; why/for which airline/what country or countries has the second battery been added?Ash Frew.

its just another backup and can be used for apu start. i heard, that those 2 batteries are not the same.. might be wrong on this one. i dont know an airline with that option but you might check some island hoppers or maybe alaska.. they have pretty much everything on board i heard (might be wrong on this one as well)

Edited January 31, 201214 yr by A32X tebsu

You know, I think the two batteries option is legacy of the Classics/originals, where the APU needed 24V DC to start, rather than the 115V AC that most ground power units provided. Imagine the frustration where you could power up the aircraft no problem with external power, but couldnt start the APU to actually get going until the slow-as-**** battery charger got enough juice to start up the APU.The two battery option I think was part of the protection to avoid this, as well as a Ricky-dink DC external power plug located next to the battery (which I believe was an option as well). Cold weather and a cold soaked APU would take the amperage if two batteries pretty quick, especially if ya didn't get a good start the first couple times. With the NG's this is a non-issue as the APU had it's own power supply which can start either with DC or AC power...So in your case Avro I think it's quite acceptable to have the single battery with ETOPS aircraft, although it probably wasn't the case with the older -400's and such.Although I imagine the second battery is also great for airstair equipped A/C and such as well.

NGs and classics are different. On the classic the second battery was used for APU start, on the NGs the aux battery is used only to power the stby power helping the main battery.The dual battery configuration is certified to supply at least 60 minutes while the single battery configuration only 30 mins.But, as technology goes ahead, the battery capacity could be increased from the 48A/h rated batteries used by our planes.For example, on classics, we had 36Amps hour batteries. I hopefully think that someone could use a more capable single battery.

I must read the document, but, is it possible that the certification does not include only the batteries?The IFSD/FSOV battery pack are rated to 150mins, plus the 30 min of the single battery gives 180 minutes of flight.The IFSD battery charger is powered by battery bus, so it will be charged untill the battery is death. With dual battery configuration you can fly the plane with the ISFD for 210 mins.

Dual battery is standart with EASA certification:

This selection installs dual 48-amp-hourbatteries and battery chargers in the EEcompartment. Sixty-minute capability is aJAA/EASA certification requirement. Thisfeature is selected when the EuropeanCertification feature package is selected.

The document I have access to does not mandate dual battery requirement for ETOPS certification.

Thanks Fabo ;)

Thanks Fabo! You've just put my mind at ease now. Thanks everyone for your answers too.Ash Frew.