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Dead Acft Batteries

Posted: Thu Mar 15, 2012 7:44 pm
by 744lover
Hi there,

Watching "Airplane Repo" yesterday when they repoed 2 ex-T4 A320 there was a moment when they couldn't connect the batteries since they were completely drained. Their solution was to fly another battery in and replace it.

My question is if connecting external power (AC or DC) shouldn't start charging the batteries. I think renting a GPU just to be able to start the APU would be much cheaper..



Thanks!
744lover

RE: Dead Acft Batteries

Posted: Thu Mar 15, 2012 8:20 pm
by BE77
Generally, if a battery is well and truly 'dead', including shorted out plates, then all the external power in the world isn't going to get it to come to life. Even if plates are not shorted, there might be no hope for getting the battery going again.

If it is only nearly dead (dating myself, but I am now reciting the 'Dead Parrot' Monty Python skit in my head), then yes applying external power might get you going.

RE: Dead Acft Batteries

Posted: Thu Mar 15, 2012 8:52 pm
by tdscanuck
Quoting 744lover (Thread starter):
My question is if connecting external power (AC or DC) shouldn't start charging the batteries. I think renting a GPU just to be able to start the APU would be much cheaper..

How will power get to the batteries? You need something to close the external power stinger contactors and get the transformer/rectifiers going (the batteries need 28 VDC, the stingers provide 400 Hz AC).

On a modern aircraft, without the hot battery bus powered, you're not going to be able to even get power flowing. It's a bootstrap problem.

Tom.

RE: Dead Acft Batteries

Posted: Thu Mar 15, 2012 9:09 pm
by KELPkid
Quoting tdscanuck (Reply 2):
How will power get to the batteries? You need something to close the external power stinger contactors and get the transformer/rectifiers going (the batteries need 28 VDC, the stingers provide 400 Hz AC).

Don't modern airliners still have an industry standard 3-pin power connector (14V/28V DC) for the batteries? We used to have GPU's at the FBO that had the 3-pin external power connector, you could use it on most GA planes (except Piper, who had their own, nonstandard single pin design) up to bizjets, and even some bigger birds like Merlins and Metros...for GA planes, you could also use a set of jumper cables that had the 3 pin on the other end and a ground vehicle battery (in which case you only got 14V power).

RE: Dead Acft Batteries

Posted: Thu Mar 15, 2012 11:29 pm
by tdscanuck
Quoting KELPkid (Reply 3):
Don't modern airliners still have an industry standard 3-pin power connector (14V/28V DC) for the batteries?

Maybe on the battery itself, but not on the outside of the airplane. To get access to it I think you'd have to remove the battery from the aircraft, at least for the big stuff.

Tom.

RE: Dead Acft Batteries

Posted: Fri Mar 16, 2012 10:58 am
by Tristarsteve
The B737-200 has a DC 28V socket in the E and E bay near the battery. If the battery is flat you can plug in a DC ground power unit and use it to power the DC, charge the battery, and start the APU.
Later aircraft with battery chargers do not have this facility.
But the few times I have arrived in the morning and found the battery left on overnight (A320 and B757), I have plugged in AC ground power and the battery has started to charge. There was enough volts left to make it all work.

RE: Dead Acft Batteries

Posted: Fri Mar 16, 2012 12:44 pm
by vc10
If I remember correctly back on the old VC-10 the power to pull in the battery contactor was obtained from the battery bus so if the battery was dead you could not pull in the contactor. So the down the route solution was [ ground power in and on line] to take a supply off the the live side of the contactor to the contactor's control terminal which allowed you to close the contactor. Once it was closed the battery bus would be powered from the GPU and so the contactor would remain closed and the battery would be charged.

Note, I am not suggesting that you short across the main terminals, as all you get is a flash and burns. Best to not leave the battery on line overnight or to fit a new batery but this was not always available away from base

littlevc10

RE: Dead Acft Batteries

Posted: Fri Mar 16, 2012 1:03 pm
by DashTrash
I took a Dash 8 from a crew one night with a deferred APU. The GPU failed before I got there, and I didn't know anything was out of the ordinary until I went to turn the batts on and the switches didn't move. They had been left on, discharging the batts when the GPU quit. I don't remember who, but someone decided to reset the GPU, which restored power of course, AND caused both batts to start a thermal runaway. They got hot enough to set off the caution lights a short time after the power was restored. I shut them off before we got the warning light.

RE: Dead Acft Batteries

Posted: Sat Mar 17, 2012 1:10 am
by dairbus
Quoting KELPkid (Reply 3):
Don't modern airliners still have an industry standard 3-pin power connector (14V/28V DC) for the batteries?

The CRJ200 has a 3-pin DC power connector under the right engine in addition to the normal 6-pin AC external connector in the nose. It's used to start the APU and provide power to the fueling panel if the APU battery and/or battery charger is on MEL. I'm not sure if external DC charges the batteries if left plugged in. Maybe someone with a little more CRJ systems knowledge can say.

RE: Dead Acft Batteries

Posted: Mon Mar 19, 2012 7:54 am
by HAWK21M
Quoting 744lover (Thread starter):
My question is if connecting external power (AC or DC) shouldn't start charging the batteries.

depending on how drained the battery really is....If its totally drained....aircraft battery charging might be ineffective or longer duration & a shop charge.
It could also be a reason to check the condition of the battery before putting it in service.....Better to replace the spare & send the u/s unit to the battery shop.

Quoting Tristarsteve (Reply 5):
The B737-200 has a DC 28V socket in the E and E bay near the battery. If the battery is flat you can plug in a DC ground power unit and use it to power the DC, charge the battery, and start the APU.
Later aircraft with battery chargers do not have this facility.

Battery cart is Very usefull on the B732s to start the APUs in case the battery is low & no GPU exists.

RE: Dead Acft Batteries

Posted: Mon Mar 19, 2012 1:37 pm
by nomadd22
I took off on a DC-3 in Brazzaville 20 years ago started by an old man pulling a cart of batteries and jumper cables. The pilot took up a collection from the passengers to pay him. I tried not to think of the plane needing to restart the engines in flight.