Maximum current from the main battery on B777?
Thread Starter
Joined: Apr 2007
Posts: 15
Likes: 0
From: Zagreb, Croatia
Maximum current from the main battery on B777?
Hello!
What's the maximum allowed current from the main battery on B777?
I can't find that information in the training manual.
Thanks in advance!
What's the maximum allowed current from the main battery on B777?
I can't find that information in the training manual.
Thanks in advance!
Joined: May 2005
Posts: 187
Likes: 0
From: Standing at P37
This is from the APU section of 747 manual. Apu and main batteries are the same. Obviously the main battery will not be subjected to the enormous current drain of a starter motor but this should give you some idea of what the battery is capable of.
"The Starter Motor is powered from an APU battery. It is rated at 7
HP at 4,500 rpm. Current drain is approximately 500 amps (1,000
amps momentarily) tapering to approximately 200 amps at starter
cutout."
"The Starter Motor is powered from an APU battery. It is rated at 7
HP at 4,500 rpm. Current drain is approximately 500 amps (1,000
amps momentarily) tapering to approximately 200 amps at starter
cutout."
Thread Starter
Joined: Apr 2007
Posts: 15
Likes: 0
From: Zagreb, Croatia
These 75 amp... did you get it from some manual, or did you just have a look at real CB?
I'd be more interested in finding out the manual which has this kind of data.
Joined: Dec 1998
Posts: 3,038
Likes: 52
From: .
BATTERIES - MAIN AND APU BATTERIES
Purpose
When ac power is not available, the main battery does these functions:
Supplies power to dc loads that are necessary for ground operation
Supplies power to all the components that deploy the RAT
Supplies standby system power until the RAT generator starts to supply power.
The main battery can supply standby system power for at least five minutes.
The APU battery supplies electrical power to start the APU.
Physical Description
The main battery and the APU batteries are rechargeable. They are fiber nickel-cadmium (FNC) batteries. Each battery weighs 106 lb (48 kg).
Each battery has two sets of ten FNC cells. The battery case is green. The case has two mounting flanges and two lifting handles. Bolts attach the mounting flanges to the airplane. The lifting handles help you connect ground support equipment (GSE) to the battery when you move it.
The battery has a terminal block and an electrical connector. The terminal block connects the high power output. The electrical connector connects control and status signals.
The battery has a temperature sensor and an overheat switch (not shown).
The battery has both ambient and battery temperature sensors, and an overheat switch (not shown). The battery cooling fan comes on when the battery gets hot.
Training Information Point
WARNING:
BE CAREFUL WHEN YOU MOVE THE BATTERY. BECAUSE THE BATTERY WEIGHS 106 POUNDS (48 KG), INJURY TO PERSONS CAN OCCUR.
Use ground support equipment to lift the main battery. You install a rack and pulley between the floor beams above the battery to help you lift it.
The APU battery attaches to a tray that you can pull out to easily remove and install the battery. When you push the tray in, there are two captive screws you must tighten to prevent tray movement.
CAUTION:
DO NOT CHARGE THIS BATTERY WITH BATTERY CHARGERS WHICH ARE NOT APPROVED FOR THIS TYPE OF FNC BATTERY. OVER-CHARGING CAN OCCUR AND SERIOUSLY DAMAGE OR DESTROY BATTERY CELLS.
The capacity of each battery is 47 amp-hours. The main battery can supply the hot battery bus loads for 10 days.
The main battery and the APU battery are interchangeable.
No maintenance is necessary for FNC batteries.
When no other power is on the airplane, the hot battery bus supplies power to the static random access memory (SRAM) of the AIMS. If you disconnect the main battery with no power to the AIMS cabinets, you lose some data. See the AIMS section for more information
Purpose
When ac power is not available, the main battery does these functions:
Supplies power to dc loads that are necessary for ground operation
Supplies power to all the components that deploy the RAT
Supplies standby system power until the RAT generator starts to supply power.
The main battery can supply standby system power for at least five minutes.
The APU battery supplies electrical power to start the APU.
Physical Description
The main battery and the APU batteries are rechargeable. They are fiber nickel-cadmium (FNC) batteries. Each battery weighs 106 lb (48 kg).
Each battery has two sets of ten FNC cells. The battery case is green. The case has two mounting flanges and two lifting handles. Bolts attach the mounting flanges to the airplane. The lifting handles help you connect ground support equipment (GSE) to the battery when you move it.
The battery has a terminal block and an electrical connector. The terminal block connects the high power output. The electrical connector connects control and status signals.
The battery has a temperature sensor and an overheat switch (not shown).
The battery has both ambient and battery temperature sensors, and an overheat switch (not shown). The battery cooling fan comes on when the battery gets hot.
Training Information Point
WARNING:
BE CAREFUL WHEN YOU MOVE THE BATTERY. BECAUSE THE BATTERY WEIGHS 106 POUNDS (48 KG), INJURY TO PERSONS CAN OCCUR.
Use ground support equipment to lift the main battery. You install a rack and pulley between the floor beams above the battery to help you lift it.
The APU battery attaches to a tray that you can pull out to easily remove and install the battery. When you push the tray in, there are two captive screws you must tighten to prevent tray movement.
CAUTION:
DO NOT CHARGE THIS BATTERY WITH BATTERY CHARGERS WHICH ARE NOT APPROVED FOR THIS TYPE OF FNC BATTERY. OVER-CHARGING CAN OCCUR AND SERIOUSLY DAMAGE OR DESTROY BATTERY CELLS.
The capacity of each battery is 47 amp-hours. The main battery can supply the hot battery bus loads for 10 days.
The main battery and the APU battery are interchangeable.
No maintenance is necessary for FNC batteries.
When no other power is on the airplane, the hot battery bus supplies power to the static random access memory (SRAM) of the AIMS. If you disconnect the main battery with no power to the AIMS cabinets, you lose some data. See the AIMS section for more information
Thread Starter
Joined: Apr 2007
Posts: 15
Likes: 0
From: Zagreb, Croatia
spannersatcx, thanks. However, notice that the excerpt you've quoted doesn't mention the maximum current which is allowed to be pulled from the battery.
I guess this question is not actually as relevant as I thought it was.
I've come to the conclusion that main battery overload cannot happen unless there is a short circuit somewhere, in which case its CB will react.
Main battery is not part of load-shedding scheme which is what I'm trying to simulate (among other things).
I guess this question is not actually as relevant as I thought it was.
I've come to the conclusion that main battery overload cannot happen unless there is a short circuit somewhere, in which case its CB will react.
Main battery is not part of load-shedding scheme which is what I'm trying to simulate (among other things).
Joined: Jul 1999
Posts: 134
Likes: 0
From: Big Sky Country
I think you may be looking at it from the wrong angle. the battery is rated at 47 amp hours.....therefore 94 amps for 30 mins, 188 amps for 15 mins etc....the only rating on the battery is the amp hour rating, the heaviest load on most aircraft will be the apu crank function. The 75 amp breaker is only for the battery charger (from the WDM). It doesn't limit the output of the APU.....hope this helps!
Thread Starter
Joined: Apr 2007
Posts: 15
Likes: 0
From: Zagreb, Croatia
I think you may be looking at it from the wrong angle. the battery is rated at 47 amp hours.....therefore 94 amps for 30 mins, 188 amps for 15 mins etc....the only rating on the battery is the amp hour rating, the heaviest load on most aircraft will be the apu crank function. The 75 amp breaker is only for the battery charger (from the WDM). It doesn't limit the output of the APU.....hope this helps!
Joined: Mar 2000
Posts: 8,571
Likes: 3
From: Arizona USA
Question please.
Scenario.
Stuck right and truly in Sokoto Nigeria, with a dead ships battery.
Only one fitted to this particular airplane (L1011).
No ground power available.
GE says...not to worry, I have a fix.
He rounds up two diesel tractor 12v batteries, hooks 'em in series, and with vey long big electrical cables threaded up through the MESC exterior hatch, , holds these on the ships battery terminals,.
This takes three guys.
Senior GE directs.
Next most senior GE holds the cables outside the MESC.
Most junior GE actually holds the cables onto the battery terminals.
The APU is then started.
After this, the ships battery begins to charge, and after the pax are loaded, we depart.
This, to me looked like a very well thought out procedure.
Can anyone comment if, in their opinion, it was not?
Oh yes, forgot to add, during the flight, the number two engine has high vibs...just short of 2.5 units with reduced throttle.
Landing at destination, the most senior GE proceeds to trim balance the #2 fan.
Took him 1.5 hours.
After this...smooth as silk.
In my opinion, these are really resourceful folks.
As the Commander, I recommended these GE's receive a bonus after the contract was completed...and they got one...a big one.
Scenario.
Stuck right and truly in Sokoto Nigeria, with a dead ships battery.
Only one fitted to this particular airplane (L1011).
No ground power available.
GE says...not to worry, I have a fix.
He rounds up two diesel tractor 12v batteries, hooks 'em in series, and with vey long big electrical cables threaded up through the MESC exterior hatch, , holds these on the ships battery terminals,.
This takes three guys.
Senior GE directs.
Next most senior GE holds the cables outside the MESC.
Most junior GE actually holds the cables onto the battery terminals.
The APU is then started.
After this, the ships battery begins to charge, and after the pax are loaded, we depart.
This, to me looked like a very well thought out procedure.
Can anyone comment if, in their opinion, it was not?
Oh yes, forgot to add, during the flight, the number two engine has high vibs...just short of 2.5 units with reduced throttle.
Landing at destination, the most senior GE proceeds to trim balance the #2 fan.
Took him 1.5 hours.
After this...smooth as silk.
In my opinion, these are really resourceful folks.
As the Commander, I recommended these GE's receive a bonus after the contract was completed...and they got one...a big one.
Joined: Aug 2005
Posts: 182
Likes: 0
From: Birchington, Kent, England
Dead Battery - Dead Lucky
411A
That was quite a novel way of getting things running. I would not recommend beginning the flight until the battery is well charged after such an event. The battery is after all your last option in the event of a major electrical failure.
This is what happened when someone else did it :
http://www.easa.eu.int/doc/Certifica...%202007-08.pdf
That was quite a novel way of getting things running. I would not recommend beginning the flight until the battery is well charged after such an event. The battery is after all your last option in the event of a major electrical failure.
This is what happened when someone else did it :
http://www.easa.eu.int/doc/Certifica...%202007-08.pdf
Joined: Dec 2004
Posts: 733
Likes: 2
From: Andalucia
Got to agree with 411A here.
Remember there is a vast difference between being stuck in Nigeria with a widebody and being stuck in Europe with it's rules and a four seater.
Always remember "Happiness is V1 at Lagos" (or anywhere else in Nigeria!)
Remember there is a vast difference between being stuck in Nigeria with a widebody and being stuck in Europe with it's rules and a four seater.
Always remember "Happiness is V1 at Lagos" (or anywhere else in Nigeria!)
Joined: Nov 1999
Posts: 70
Likes: 0
From: UK
battery current
In a previous role i carried out a lot of research into aircraft batteries, and did a number of tests with various batteries and their performance at various temperatures during APU starts. The instantaneous current drawn the moment the starter is energised and the APU begins to turn during the start sequence will be around the 1200-1800amp mark. It will fall away fairly rapidly (2-5 secs) to around 400 amps and will continue to decrease as the APU accelerates towards starter cut-out. A typical APU start will draw about 4% of available battery capacity at 20 deg C.
I have some actual curves at home somewhere, but none for the 777 i'm afraid.
high-flyer
I have some actual curves at home somewhere, but none for the 777 i'm afraid.
high-flyer
