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787 Batteries and Chargers - Part 1

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787 Batteries and Chargers - Part 1

Old 23rd Jan 2013, 18:19
  #101 (permalink)  
 
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Wasn't the Boeing PR about "not overcharged" BEFORE their "visit" to securaplane (funny in context BTW)?

So if no overcharge, why talks/inspections with the manufactor of the chargers?
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Old 23rd Jan 2013, 18:22
  #102 (permalink)  
 
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Don't Securaplane supply the integrated system/monitoring?

hetfield, I don't know about you, but the name "Securaplane" makes me think of a chain and padlock on the Nosewheel?


Last edited by Lyman; 23rd Jan 2013 at 18:24.
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Old 23rd Jan 2013, 19:12
  #103 (permalink)  
 
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Quote from Bsieker:

“They are all variable frequency AC, depending on generator rpm, so I guess it's not a good idea to try to power one bus from two different sources at the same time.”

Thanks for that, and the list of 4 AC distribution buses. No constant-speed drives (reminiscent of the B707). Sounds like a flight-engineers dream, so they must have a very good automatic load-transfer system to do the job for mere pilots...

sb_sfo,

Can you confirm you are saying that the R/H APU starter/generator (as well as the L/H) can receive 115Vac from either the ship’s or external? So would it be true to say that the R/H APU starter/generator can receive 115Vac from any of the 3 potential power sources, including the APU battery (via its Start Power Unit), but the L/H one can only get it from ship’s or external?

I wonder what the initial load is on the 28Vdc APU battery, and if it is modulated. As I’ve noted elsewhere, the initial (28Vdc) load on the A320 starter (for example) is about 1000 amps, which is shared between two NiCd batteries if the TRs are not powered.

Can you tell me the possible source(s) of power to the APU battery charger? And please confirm that the APU battery is able to power lighting for towing and maintenance purposes, but otherwise is dedicated to APU start?

Sorry for such a lot of questions!
Chris
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Old 23rd Jan 2013, 19:19
  #104 (permalink)  
 
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"Securaplane" makes me think of a chain and padlock on the Nosewheel?
lol, me too....

In context with burning batteries it's kind of sarcasm
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Old 23rd Jan 2013, 19:28
  #105 (permalink)  
 
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IAM WAGing, the APU starter motor draws 25-30 amps, at 115vAC, 2-3 horsepower?

The DC cables at the APUBATT are copper braid (for surface area) and perhaps ten times the weight of indexed AC wires? I saw similar cabling on automobiles from the thirties and forties.

Dinosaur. At least in that position.

Last edited by Lyman; 23rd Jan 2013 at 19:31.
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Old 23rd Jan 2013, 19:35
  #106 (permalink)  
 
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Cell phone battery test

Salute!

Well, I didn't die and sure enough the battery got hot.

I wimped out and cracked the case and then used a garden hose from 15 feet away ( 3 meters for you other guys).

It started to smoke about a minute into the run. And then it stopped smoking and cooled down in about 3 more minutes.

Only conclusion I can justify from the rough test is that a mechanical crack and exposure to high humidity could cause the Li-ion to get real hot. this was only a 1 amp-hour doofer, but I couldn't hold it in my hand.

Anyway, was fun to run a test, however ill-conceived and planned.
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Old 23rd Jan 2013, 19:39
  #107 (permalink)  
 
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Sorry all but can not stop myself from posting this clip from the current "google ads" at top of the page:

Energizer® Batteries
Everyone Needs a Battery They Can Rely On. Find Yours Today.
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Old 23rd Jan 2013, 19:47
  #108 (permalink)  
 
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gums

15 feet = 3 meters (for the rest of us guys......)


How are things working in your world?

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Old 23rd Jan 2013, 20:13
  #109 (permalink)  
 
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Cascading failure scenario

It was reported that no overcharging of the battery as a whole may have occurred. This may have been derived from FDR recording of the bus voltage.

A weight loss of 4kg of (one) of the batteries was also reported. This amount is indicative of substantial loss of electrolytic and insulator material of multiple cells.

All this happened very quickly, perhaps faster then thermal runaway by conduction of thermal energy amongst cells.

In a possible scenario, a single cell short would result in the battery voltage dropping, which would have to be detected and the battery quickly disconnected by a means in order to prevent the bus (or charger) driving remaining good cells into redline above 4.3V, which could result in a cascading increase of cell voltages as more cells reduce voltage and leading to the rapid destruction of all cells.

Thus it would be interesting to know whether some cells are shorted and how the battery is decoupled/protected from tied buses.
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Old 23rd Jan 2013, 20:18
  #110 (permalink)  
 
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It was reported that no overcharging of the battery as a whole may have occurred. This may have been derived from FDR recording of the bus voltage.
Yes, but this is just sugar for the public/press.

An individual overcharge MAY have occurred, 'cause every single cell (8) has to be charged and controlled seperatly. I'm afraid, this is not recorded...


Why is BOEING visiting secuaraplane......?

Last edited by hetfield; 23rd Jan 2013 at 20:21.
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Old 23rd Jan 2013, 20:31
  #111 (permalink)  
 
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Discharge limits

Cells are rated for max discharge at 5C, thus 325A. Inner resistance is 3milliohm, which seems a fairly high inner resistance for this capacity.

At 300A load, the internal voltage drop would be 900mV and the power dissipation 270W per Cell, or 2160W per battery. Thats really stressful.

At 1000A, power dissipation would be 3000W per cell.

It would be prudent for the starter not to pull more than 150A (5KW) sustained.
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Old 23rd Jan 2013, 21:06
  #112 (permalink)  
 
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Chris

The other specific answers are gonna have to wait a while- don't have the material handy. But I noticed one thing- you seem to be under the impression that 777s have more than one main battery. The ones I work on have a main and APU battery, and unless you want to count the fuel spar valve batteries, I know of no others.

As to the rest, yes the APU battery can only send power to the R/h ASG. The APU battery charger is powered through the F/O instrument bus, and the APU battery supplies lights when towing.

More later
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Old 23rd Jan 2013, 21:49
  #113 (permalink)  
 
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Critical battery

@ saptzae #109 and 111

Touching the core of the (probable) main issue.

I suspect they didn´t design means to "remove" the battery from the bus.

Important comments from HK!

Question: Who produces these big cells in China?

Last edited by RR_NDB; 23rd Jan 2013 at 21:56. Reason: Typo
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Old 23rd Jan 2013, 22:12
  #114 (permalink)  
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hetfield wrote:
Why is BOEING visiting secuaraplane......?
Do you mean rather than the NTSB or FAA?
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Old 23rd Jan 2013, 22:24
  #115 (permalink)  
 
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Individual cells monitoring (AND also CONTROL) during recharge

hetfield,

Ideally the charging would be controlled to each cell. (because they are not identical. And Temp and Aging are extra factors). In the config of the Thales battery the charging current SEEMS TO BE THE SAME* for all cells). The control of the voltage just allowing a derating during the charging (extending the time). But when discharging (APU start, etc.) voltage control is useless. Just for recording, if so.
If the internal data recorder is not properly designed we may never know what led to BOS and TAK incidents.

The plane FDR certainly is not used to look inside a battery. Should be. If airliners would use these batteries for HIGH CURRENTS. It´s relatively simple.

This comment is also to answer A33Zab question on my concerns on other Li Ion applications in 787 and 380. Problems are much likely with high current (specially charging). Trickle charging (to keep the cells "floating" to a safe value is not dangerous.

There are other considerations on the use of Li Ion on an airliner. Location can be critical, in case of a catastrophic failure.

I actually have objections on the positioning of them in the 787. Specially the APU battery. (Nearby electronics).

(*) There is a possible charger architecture with controlled currents (closed loop) for each cell. It allows quick charge "respecting the personality of each cell during her aging and under different temperatures". I will assembly it for my electric bike pack. I would like to know if what A33Zab commented on A350 was with this concept. We may find this in Patents Database. (USPTO, SPACENET, etc.) The concept is one charger for each cell. I assume the designers put everything possible (for safety) in the 787 subsystems design. The same i imagine in A380 Li Ion application and A350 (that will benefit from 787 teething issues).

Last edited by RR_NDB; 24th Jan 2013 at 00:20. Reason: Improved text after revision made
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Old 23rd Jan 2013, 22:46
  #116 (permalink)  
 
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Quote from sb_sfo:
"But I noticed one thing- you seem to be under the impression that 777s have more than one main battery. The ones I work on have a main and APU battery, and unless you want to count the fuel spar valve batteries, I know of no others."

You are right, I did post that the B777 had two main batteries, plus the APU one. My Google search for "B777 electrical system" had produced a nice clear schematic with two, which I now see is for a generic system. Thanks for setting me straight on that, and I look forward to more info on the B787 points.

(EDIT)
Have now found and amended my post. Looks like all currently-operating Boeing types have one main battery, plus a dedicated APU battery?

Last edited by Chris Scott; 24th Jan 2013 at 10:18. Reason: Added "EDIT"paragraph.
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Old 23rd Jan 2013, 23:04
  #117 (permalink)  
 
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My opinion of the APUBATT and EE bays location is that it is optimal. It cannot go in the tail cone (unpressurized), and would be too far from its best position, the forward most area of the cargo hold just aft of the wing box. This is equi-distant from the TWO main engines, and co locates generated and usable power. Wiring is resistance, so the APUBATT belongs closest to the APU but equidistant from #1 and #2 engines.

The Main battery serves systems that are closer to the cockpit, instruments and flight controls, so belongs just aft the cockpit and in the hold closest to the nose wheel structure. This affords best use of the hold's volumes, shortens conductor runs optimally, and affords accessibility from outside.

bear

Last edited by Lyman; 23rd Jan 2013 at 23:04.
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Old 24th Jan 2013, 01:38
  #118 (permalink)  
 
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Words on that graph

archae86:

My apologies for the delay in commenting.

I discussed it with him extensively a few hours ago.
Indeed, make us very interested.

The comparison curves were all measured on 18650 cells--a size and form factor often used inside those black brick laptop batteries we have all seen.
Did you use or tested the protected 18650´s?

The cells they use are small enough that the energy release from a single one should not endanger crew or vehicle.
The big adjacent cells in the Thales battery concerns me.

Looking at the Thales/Boeing design and the FAA special considerations, it appears that the approach was to assure cell failure would never occur--as it seems self-evident that no serious measures to avert propagation to adjacent cells were employed, nor were serious measures to contain damage to nearby systems.
TAK incident and specially BOS showed dramatically they failed.

...I wonder if all concerned will remain convinced that all other possible causes of cell failure are sufficiently unlikely to make this approach prudent.
This error is being paid by Boeing with threatening consequences.

Call this Tesla-like.
Tesla just used the perhaps the most important characteristic of a good design:

Fault Tolerance and Graceful Degradation.


It is awkward when "never" happens

...as happened with the IPT disc on a Rolls-Royce Trent 900 on Qantas flight 32, and has happened on these two 787 episodes. Examples everywhere.

Thanks again for excellent post and answer.
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Old 24th Jan 2013, 03:58
  #119 (permalink)  
 
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Originally Posted by Lyman
15 feet = 3 meters (for the rest of us guys......)
Now I understand how you guys are sooooo... tall.

Make Google your friend ....

"15 feet = meters" will get you down to size.
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Old 24th Jan 2013, 04:17
  #120 (permalink)  
 
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Originally Posted by mm43
:
Originally Posted by Originally Posted by Lyman
15 feet = 3 meters (for the rest of us guys......)
Now I understand how you guys are sooooo... tall.

Make Google your friend ....

"15 feet = meters" will get you down to size.
As I tell female acquaintances, this <------------------------>

is 8 inches or 300millimetres...

Ok, OK, I'll make sure the door doesn't hit it on the way out...
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