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BreninTW
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Batteries Used On Previous Generation Aircraft

Thu Jan 17, 2013 5:03 am

I'm curious, it seems to me that the major problem with the 787 is the Li-ion batteries that have been used.

What type of batteries were used in previous generations of aircraft? I'm assuming they weren't lead-acid batteries, but were they Li-ion?

I work in the computer industry, so I'm fairly familiar with the problems encountered with shipping Li-ion batteries ... it seems counter-intuitive to me (as a rather ignorant outsider) to use the same type of battery on a passenger aircraft when the jolly things are are not allowed to be transported on passenger flights.

I understand that aviation-grade Li-ion batteries are almost certainly more thoroughly tested and manufactured under much stricter oversight than computer-grade batteries, but it's still surprising to me.

EDIT: Grammar correction.

[Edited 2013-01-16 21:36:47]
 
fr8mech
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RE: Batteries Used On Previous Generation Aircraft

Thu Jan 17, 2013 5:11 am

Batteries used on transport category aircraft (B787 aside) are almost exclusively Ni-Cad.

Quoting BreninTW (Thread starter):
it seems counter-intuitive to me (as a rather ignorant outsiders) to use the same type of battery on a passenger aircraft when the jolly things are are not allowed to be transported on passenger flights.

Not a rare issue on aircraft. O2 bottles, fire bottles, batteries and a few other things can't be shipped, but are installed on aircraft.
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BreninTW
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RE: Batteries Used On Previous Generation Aircraft

Thu Jan 17, 2013 5:35 am

Quoting fr8mech (Reply 1):
Batteries used on transport category aircraft (B787 aside) are almost exclusively Ni-Cad

Thanks for that.

Any chance of the 787 switching back to Ni-Cad?
 
Mir
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RE: Batteries Used On Previous Generation Aircraft

Thu Jan 17, 2013 5:36 am

We've got a lead-acid on ours (a Citation). There's also an option for a NiCad battery.

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1337Delta764
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RE: Batteries Used On Previous Generation Aircraft

Thu Jan 17, 2013 5:51 am

So, what about NiMH? They offer somewhat more capacity than NiCad, though not as much as Li-ion.
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tdscanuck
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RE: Batteries Used On Previous Generation Aircraft

Thu Jan 17, 2013 12:43 pm

Quoting BreninTW (Thread starter):
I work in the computer industry, so I'm fairly familiar with the problems encountered with shipping Li-ion batteries ... it seems counter-intuitive to me (as a rather ignorant outsider) to use the same type of battery on a passenger aircraft when the jolly things are are not allowed to be transported on passenger flights.

The major difference between transport and use is the conditions of the installation...for installed stuff, you can put on containment, isolation, detection, and sometimes supression. For the cargo holds (i.e. shipped) you can only do detection and, maybe, suppression. You have a lot less control over what happens in the event of a failure, so the safety fault tree is a lot different.

Quoting BreninTW (Thread starter):
I understand that aviation-grade Li-ion batteries are almost certainly more thoroughly tested and manufactured under much stricter oversight than computer-grade batteries, but it's still surprising to me.

It's similar to how you can't ship jet fuel but you can stuff the airplane full of it.

Tom.
 
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RE: Batteries Used On Previous Generation Aircraft

Thu Jan 17, 2013 1:53 pm

Quoting 1337Delta764 (Reply 4):
So, what about NiMH? They offer somewhat more capacity than NiCad, though not as much as Li-ion.

From Wikipedia, which I know can be a problem on some subjects, but is usually very good with actual facts.

Quote:
The significant disadvantage of NiMH batteries is the high rate of self-discharge; NiMH batteries lose up to 20% of their charge on the first day and up to 4% per day of storage after that
 
nomadd22
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RE: Batteries Used On Previous Generation Aircraft

Thu Jan 17, 2013 2:47 pm

NiMh are also harder to properly charge, particularly that last 10%. We regret getting them because of the self discharge problem. We either have to pull out and charge hundreds of them every month, or they're useless when we need them.
They're not anywhere near as bad as Wiki says, but a lot worse than other types.
NiCads have the same problem with swelling and overheating when you overcharge or overuse them, but they don't go nuclear like Lithiums can.
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AirframeAS
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RE: Batteries Used On Previous Generation Aircraft

Thu Jan 17, 2013 4:38 pm

Quoting BreninTW (Reply 2):
Any chance of the 787 switching back to Ni-Cad?

I don't think the 787 ever had Ni-Cad batteries to begin with.
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Stitch
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RE: Batteries Used On Previous Generation Aircraft

Thu Jan 17, 2013 4:45 pm

Quoting BreninTW (Reply 2):
Any chance of the 787 switching back to Ni-Cad?
Quoting AirframeAS (Reply 8):
I don't think the 787 ever had Ni-Cad batteries to begin with.

Correct. The same Li-Ion battery is used for both the main and APU battery (so that if the main battery goes MEL, you can install the APU battery in it's stead).
 
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CALTECH
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RE: Batteries Used On Previous Generation Aircraft

Thu Jan 17, 2013 5:39 pm

As told to us, a NiCad battery with the power available to be used on the 787 would weigh 300+ lbs, a monster. Add the identical APU battery, as Tom/tdscanuck stated elsewhere, and that is some serious weight there. A 777 NiCad battery weighs about 106 lbs. The 787 LiIon battery weighs a mere 66 lbs. It more than likely that the LiIon battery is here to stay for some other issues as well. The APU battery is like a onboard spare for the main battery.
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kanban
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RE: Batteries Used On Previous Generation Aircraft

Thu Jan 17, 2013 6:12 pm

posted this question on the other thread.. maybe it more appropriate here

Yuasa makes these batteries for many land surface operations, trains, trucks, etc. and seem to have no problems. Possibly could the problem be related to the pressure differentials when flying... ie water boils at a lower temperature at elevation, so could the organic fluid in these batteries "boil" at altitude and leave the anodes/cathodes bare and in contact?
 
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CALTECH
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RE: Batteries Used On Previous Generation Aircraft

Fri Jan 18, 2013 3:15 am

Quoting kanban (Reply 11):
posted this question on the other thread.. maybe it more appropriate here

Yuasa makes these batteries for many land surface operations, trains, trucks, etc. and seem to have no problems. Possibly could the problem be related to the pressure differentials when flying... ie water boils at a lower temperature at elevation, so could the organic fluid in these batteries "boil" at altitude and leave the anodes/cathodes bare and in contact?

No, sure it was tested depressurized at altitude. And this electrolyte is more of a paste than liquid. But it probably does 'boil' during a thermal runaway.
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nomadd22
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RE: Batteries Used On Previous Generation Aircraft

Fri Jan 18, 2013 3:37 am

Anything on a plane needs to be rated for the pressure it's operated at. And, since all the 787 batteries aren't in flames, it's obvious something is different with the ones that were. I'd bet dollars to doughnuts that it turns out to be a Yuasa quality control issue. Something as simple as not having series cells well enough matched. Hopefully, something that can be temporarily fixed by a monthly PM or whatever until the permanent fix is in.
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prebennorholm
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RE: Batteries Used On Previous Generation Aircraft

Fri Jan 18, 2013 3:44 am

Quoting CALTECH (Reply 10):
As told to us, a NiCad battery with the power available to be used on the 787 would weigh 300+ lbs, a monster.
Quoting CALTECH (Reply 10):
The 787 LiIon battery weighs a mere 66 lbs.

There is something wrong with these numbers. Power density on Li-Ion compared to Ni-Cd is in the 2.5 to 3 factor frame. So a potential 787 Ni-Cd battery would be like 165 - 200 lbs. Still an unpleasant addition, which has to be multiplied by two since there are two batteries.

Quoting rfields5421 (Reply 6):
The significant disadvantage of NiMH batteries is the high rate of self-discharge; NiMH batteries lose up to 20% of their charge on the first day and up to 4% per day of storage after that

That disadvantage is in many cases compensated by the higher power density compared to Ni-Cd.

But for use on airliners Ni-MH is irrelevant because they perform extremely badly when cold. For starting an APU on a frosty morning they would have to be crazily oversized. All batteries perform worse at low temperature, but Ni-Cd and Li-Ion (also lead acid) lose performance at low temperature at a much lower rate than Ni-MH.

Ni-MH still maintains the capacity at low temperature. But it has a very high voltage drop when high power output is required at low temperature.
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rwessel
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RE: Batteries Used On Previous Generation Aircraft

Fri Jan 18, 2013 7:51 am

Quoting prebennorholm (Reply 14):
There is something wrong with these numbers. Power density on Li-Ion compared to Ni-Cd is in the 2.5 to 3 factor frame. So a potential 787 Ni-Cd battery would be like 165 - 200 lbs. Still an unpleasant addition, which has to be multiplied by two since there are two batteries.

I don't understand the application well enough, but Li-Ion's have a rather flatter discharge curve down to their "knee" and the knee tends to happen a bit further down the discharge graph. You might need ~20% more nominal capacity in a NiCd if you need to keep the voltage up.
 
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CALTECH
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RE: Batteries Used On Previous Generation Aircraft

Fri Jan 18, 2013 2:49 pm

Quoting prebennorholm (Reply 14):
There is something wrong with these numbers. Power density on Li-Ion compared to Ni-Cd is in the 2.5 to 3 factor frame. So a potential 787 Ni-Cd battery would be like 165 - 200 lbs. Still an unpleasant addition, which has to be multiplied by two since there are two batteries.

What's wrong with the numbers told to us by the manufacturer ? A 777 battery weighs in at 106 lbs and the 787 needs a battery that has approximately 3 times the stored power of the 777 as relayed to us by the manufacturer.
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Starlionblue
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RE: Batteries Used On Previous Generation Aircraft

Sat Jan 19, 2013 12:30 am

Quoting CALTECH (Reply 16):
What's wrong with the numbers told to us by the manufacturer ? A 777 battery weighs in at 106 lbs and the 787 needs a battery that has approximately 3 times the stored power of the 777 as relayed to us by the manufacturer.

That's because the 787 is "all electric" with no bleed air system. It needs way more battery power as backup.

BTW does the 787 have electric engine start since it has no pneumatics?
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Fabo
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RE: Batteries Used On Previous Generation Aircraft

Sat Jan 19, 2013 1:48 am

Quoting Starlionblue (Reply 17):
BTW does the 787 have electric engine start since it has no pneumatics?

Yes.
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Starlionblue
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RE: Batteries Used On Previous Generation Aircraft

Sat Jan 19, 2013 2:26 am

Quoting Fabo (Reply 18):
Quoting Starlionblue (Reply 17):
BTW does the 787 have electric engine start since it has no pneumatics?

Yes.

Run by the APU I guess. But still explains the beefy batteries.
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CALTECH
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RE: Batteries Used On Previous Generation Aircraft

Sat Jan 19, 2013 1:50 pm

Quoting Starlionblue (Reply 17):
BTW does the 787 have electric engine start since it has no pneumatics?

Yes, and as we are told, one can start both engines at the same time unlike most 'bleed air' transport aircraft.
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Tristarsteve
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RE: Batteries Used On Previous Generation Aircraft

Sat Jan 19, 2013 5:38 pm

Quoting CALTECH (Reply 20):
Yes, and as we are told, one can start both engines at the same time unlike most 'bleed air' transport aircraft.

Who told you that?
To start a B787 engine you need all the power from both APU generators, or Three Ground Power Units.
I suspect there is some way you can isolate this so that the APU supplies one side, and the 3 GPUs supply the other, but I wouldn't expect anyone to do it. Mainly because that when the engine is running, you then have to go and remove the GPU that is plugged into the AFT EE bay, behind the engines.
Not something I would recommend.
 
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CALTECH
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RE: Batteries Used On Previous Generation Aircraft

Sun Jan 20, 2013 2:04 am

Quoting Tristarsteve (Reply 21):
Who told you that?.

Our glorious Training Instructors as told from Boeing.

Quoting Tristarsteve (Reply 21):
To start a B787 engine you need all the power from both APU generators, or Three Ground Power Units. I suspect there is some way you can isolate this so that the APU supplies one side, and the 3 GPUs supply the other, but I wouldn't expect anyone to do it. Mainly because that when the engine is running, you then have to go and remove the GPU that is plugged into the AFT EE bay, behind the engines.
Not something I would recommend.

Incorrect.

As from Boeing and my manuals,

http://www.boeing.com/commercial/airports/acaps/787sec5.pdf

"Normal engine start for the 787 uses the APU to provide electrical power. If the APU is inoperative or unavailable, an engine start can be accomplished using a minimum of two 90 kVA external ground power units connected to the two forward external receptacles. Boeing recommends using three 90 kVA ground power sources to minimize the effect on cabin load shedding of ventilation, In Flight Entertainment, and cabin lighting."

Minimum of 2 X 90 kVA power sources for 180 kVA per engine. The third External Power pickup is for faster starts and minimize load shedding. Simultaneous engine start needs minimum of 360 kVA. Each APU generator has a rating of 225 kVA for a total of 450 kVA, more than enough for a simultaneous engine start. Unless, of course, Boeing and our Training Instructors have it wrong.

http://www.boeing.com/commercial/aer...rticles/qtr_4_07/article_02_4.html

"The power source for engine starting may be the APU generators, engine-driven generators on the opposite side engine, or two forward 115 VAC ground power sources. The aft external power receptacles may be used for a faster start, if desired."

At about 1:35, both engines seem to be turning, simultaneously.

http://www.youtube.com/watch?v=hLummpF9DHo

This one shows it really good in fullscreen 1080P hd.

http://www.youtube.com/watch?v=2Q6AEkpNtiU

This passenger says it also on a United Flight,

http://forums.vwvortex.com/showthrea...First-flight-on-the-787&p=79998410

"We pushed back and started up. The start sequence is something I've never experienced. They start both engines simultaneously (like the 777) but there is a lot of vibration, I'm guessing with them being a little out of sync, that you get about a minute long full body massage. The engine noise is non existent though."

When I was checking out the 787 Simulator, we also did simultaneous engine starts. Would say my outstanding training is correct, both engines can be started simultaneously.   

[Edited 2013-01-19 18:21:44]
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tdscanuck
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RE: Batteries Used On Previous Generation Aircraft

Mon Jan 21, 2013 6:01 am

Quoting Starlionblue (Reply 17):
That's because the 787 is "all electric" with no bleed air system. It needs way more battery power as backup.

It's not directly because of the all-electric architecture, because the things that used to be pneumatic but are now electric aren't using battery power anyway. It's mostly because the 787 avionics and fans need more juice to run (this would have been true with or without the pneumatic system).

Quoting Starlionblue (Reply 17):
BTW does the 787 have electric engine start since it has no pneumatics?

Yes. The drive the generators backwards as starters.

Quoting Tristarsteve (Reply 21):
Quoting CALTECH (Reply 20):
Yes, and as we are told, one can start both engines at the same time unlike most 'bleed air' transport aircraft.

Who told you that?

Boeing. I've seen it many times, in both the sim and the real aircraft.

Quoting Tristarsteve (Reply 21):
To start a B787 engine you need all the power from both APU generators, or Three Ground Power Units.

No. To start one engine you need one APU generator or two GPUs. Having more will make the start go faster and cause less load shedding but it will start just fine. If you want a simultaneous start you need both APU generators (one to each engine).

Tom.
 
kalvado
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RE: Batteries Used On Previous Generation Aircraft

Wed Jan 23, 2013 12:26 am

Not exactly on topic - but are (were) there any plans to retrofit older types with Li batteries? I am thinking mostly narrow-bodies, where certification costs can be spread between many frames.
I can see that envisioned as a low-hanging fruit to save a few pounds of weight once first battery and enclosure design is certified with 787 and most issues are worked out. Apparently such projects would be put on hold with latest 787 problems, but would that make any sense to begin with?
 
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CALTECH
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RE: Batteries Used On Previous Generation Aircraft

Thu Jan 24, 2013 2:52 pm

Quoting kalvado (Reply 24):
Not exactly on topic - but are (were) there any plans to retrofit older types with Li batteries? I am thinking mostly narrow-bodies, where certification costs can be spread between many frames.
I can see that envisioned as a low-hanging fruit to save a few pounds of weight once first battery and enclosure design is certified with 787 and most issues are worked out. Apparently such projects would be put on hold with latest 787 problems, but would that make any sense to begin with?

Probably not as the certification costs probably outweigh the cost savings. These batteries are very expensive right now.
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