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ANA TAK model
Hi,
inetdog: ...a large part of the connector appears to be totally missing, not just cut. That is more consistent with a high amperage vaporization of the metal than with a gas jet cut... Screw just disappeared. Section of strap too. The model is: Short to ground (a fact) discharged (fortunately) the battery (reducing thermal runaway risks and duration) and this high (1,000 Amps +) current opened the battery (Voltage recorded, after fluctuation, went to zero) ...although both events may have occurred as slightly different times. |
Look more carefully to what i posted
Hi,
Bill, That is the current design. := Does nothing to prevent a thermal runaway. You will reduce drastically the likelihood of a DANGEROUS battery thermal runaway. BOS JAL was! ANA TAK, NOT!. A cell thermal runaway (with separated cells) is not a major problem. A noble attempt to.....what? To better "balance" charging? The BAD battery algorithm will be reviewed, right? Letīs improve it. The opportunity is now to even derate the battery, if safety is the goal. And if this derating is not possible, SWITCH to Ni Cdīs as most of us would like. :mad: Itīs an ABSURD whatīs happening. Itīs just a battery. :mad: All this does is underscore how badly Thales and BOEING designed the system in the first place. "INFLIGHT FIRE MANAGEMENT SYSTEM" |
Back-of-a-fag-packet calculation:
Cell voltage 3.7V, capacity 65Ah, mass 2.75Kg, specific heat capacity 1,000J/KgK (guess) (3.7 * 65 * 3600) / (1000 * 2.75) = 314K The energy stored is enough to raise the internal temperature 300+degs in self-discharge before you take all the subsidiary exothermic reactions that go with thermal runaway. Looking at videos of disrupted lithium cells it is enough in some cases to take them to white heat and melt metal casings. I can't see an obvious way to stop the heat bleeding through to other cells - the electrical bonding between them would carry significant flux even if the insulation of the walls was perfect. As it stands at the moment, my personal opinion is that it is possible to have a safe installation of li-ion batteries in an airliner but Boeing have chosen the wrong chemistry together with inadequate safeguards. I agree with the NTSB that fire on board is something that just isn't acceptable, even if you think it could be contained. :ugh: |
A backup that heats, smokes and expel fire? And not works as a backup?
Hi,
FullWings: I can't see an obvious way to stop the heat bleeding through to other cells - the electrical bonding between them would carry significant flux even if the insulation of the walls was perfect. As it stands at the moment, my personal opinion is that it is possible to have a safe installation of li-ion batteries in an airliner but Boeing have chosen the wrong chemistry together with inadequate safeguards. I agree with the NTSB that fire on board is something that just isn't acceptable, even if you think it could be contained. :ugh: Problem is. You need a dependable battery. Thatīs one (perhaps the more important) to switch now back to Ni cd. In the meantime a redesign would restore the confidence. ...even if you think it could be contained. |
re-design the batteries so they are round, take the reduction in cap, or make it a little bigger...the space between the cells could be filled with non-reactive material...(just like all the other LI systems out there!):{
the titanium shell cert would be 3 months....and it does not look like the FAA is even entertaining this... to redesign the battery/charging/electrical system will take how long to design and then cert? meanwhile, production rate is about what, 40 a month? at least 120 ac stored somewhere waiting for the temp fix... for 6 months, 240 ac that would then have to be re-fitted, not to mention the ac already parked.... looks like Boeing should have let them go on strike, just to save the parking space... |
"Convoluted mess"
Hi,
FlightPathOBN: to redesign the battery/charging/electrical system will take how long to design and then cert? meanwhile, production rate is about what, 40 a month? at least 120 ac stored somewhere waiting for the temp fix...for 6 months, 240 ac that would then have to be re-fitted, not to mention the ac already parked... looks like Boeing should have let them go on strike, just to save the parking space... |
from the coal face
Home - Boeing 787 Updates
Interesting link here. Quote:- When the going gets tough, program teams get going:ugh: |
from that site...
"No battery-related incidents occurred before January 2013, when the airplane experienced two events." Replacing over 100 of them so far is certainly an issue with the design and viability of the design. |
APU battery of ANA incident aircraft shows anomalies
Progress in pinpointing Primary failure.
The plane's auxiliary power unit (APU) battery, which powers its systems when it is on the ground, was found to have swelling in two of its eight battery cells, the official said. |
From the Boeing website referred to above, my bolding:
"Matching the right battery to the requirements After extensive testing, Boeing ultimately selected the lithium-ion type battery because it has the right functionality and chemistry to deliver a large amount of power in a short period of time to do a high-energy task like start a jet engine. It then has the ability to recharge in a relatively short period of time so that it is available for the critical backup role that it plays during flight. Earlier commercial airplane models, such as the 777, 747 and MD-11, used nickel cadmium (NiCd) batteries, which are heavier, larger and less powerful. Surely the bit I bolded there would preclude just stuffing it in a box to contain the fire? |
There can be no conflict in the regulations. ICAO has ruled no large Lithium Ion batteries on board aircraft.
The DOT (Department of Transportation) ruled, hastily, to allow these batteries in cargo, just as Boeing was hurriedly shipping them to replace batteries in the field. That raises a flag. After the grounding, and an initial statement of support for Boeing, the chief, Ray LaHood, resigned the position. Part of politics is anticipation. NTSB are investigating the certification of the 787. To get fire acceptable in there, somewhere, will take some interpretation. What is the current status of this cargo/Battery? There is argument that since the FAA do not specify fire as disqualifying in their regulations, that it is allowed, if contained. To contain is to prevent from spreading.... It is the first step in fighting a fire. The second step is to extinguish the fire. As we see in Boston, extinguishing this type of fire is not generally possible. What are the regulations per the transport of a box of non-extinguishable fire, aboard a flammable airplane? In non accessible areas of the airframe? |
I'd be very wary of using a Ti alloy, just another lightweight solution to a bigger problem. 400 Degrees plus and you are in big trouble.
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Since entering service, Boeing 787 Lithium-Ion batteries, each with eight cells, have logged more than 2.2 million cell-hours on the ground and in the air during more than 50,000 flight-hours. No battery-related incidents occurred before January 2013, when the airplane experienced two events. Investigation into these events is in progress. Well! what a complete load of pseudo-engineering bollocks :yuk: 2.2 million "cell-hours" on the ground?-REALLY!(less 50,000 actual flight hours*) well, fxxk me with a fountain-pen, my Ford has had about 8 billion millilitres of Diesel through it's system, with NO "incidents"...keep changing the filter sees to that!:} (is that similar to "keep changing the batteries when they go T.U.?" Where they find these smart-ass political -spinner oil-slick smarmy bull****ters from, I've no idea. As a potential Boeing Pax. I won't believe another word from them,if this is how they patronise their market. So, let's do the sums...the "battery hours" are actually nearer 250,000(assuming that the quoted 50Khours was "battery time" and not "cell-time":} ) BUT WAIT!..each aircraft has 2 batteries....50 grounded,=100 batteries...add 150 changed-out....250 total used stock so the cumulative service life of these aircraft, (land and ground,-their figures) is 250,000 hours that means a total service-life of 1,000 hours per battery OR 16 dollars an HOUR ....32 DOLLARS an HOUR, EVERY hour per aircraft....remind me, how much is a Laptop battery? price? hours life? Oh! I see, I got it wrong! the cost doesn't matter as long as it's a good, reliable ,fit-for purpose system. WOT? NONE of the above?:O Some bean-counter's being grossly overpaid for a stupendous level of incompetence! * also back-of-a-fag-packet calculations. |
After extensive testing, Boeing ultimately selected the lithium-ion type battery because it has the right functionality and chemistry to deliver a large amount of power in a short period of time to do a high-energy task like start a jet engine. The main bat has nothing to do with engine start. A ni-cad will do the job of starting the APU. Someone at Boeing got their wires crossed. :suspect: |
Battery integration
I am joining late on this thread, but after reading through the 37 pages of posts. There appears to a lot of battery experts on this thread, discussing about temp sensors, cell separation etc.
But no body seems to discuss why 1. Boeing never experienced this problem during 3 years of flight tests and ANA during nearly an year of operation. 2. Is it just a coincidence that we have 2 fire incidents in one month. 3. Surely the battery would have gone through a rigorous testing before manufacture and it is difficult to imagine that there were no problems at all with this compact design of a highly volatile chemistry. 4. What was the reason for 100 batteries removed before these incidents. No alarms were raised for a new aircraft. 4. From the data available with me, these batteries perform almost the same function as on Boeing 777, except for emergency breaks from Main battery, in case of a total loss of power landing. Then why B787 require a battery that can give 150 amps? Can some one with the required knowledge and info enlighten. It is sad to see Boeing fortify this volatile battery with thicker walls just to get the airplanes airborne again. You only need another incident, even if contained fully, for the travelling public horrified even to go near the aircraft. Remember the well engineered DC10 that disappeared along with the company. Boeing's venture on a bleed-less road was risky enough, but this route is a very risky for them and the airlines. I hope FAA and NTSB will think twice before they give the green signal. := |
Having read both threads on this issue there is a lot of good information being provided. The swelling of the packs is quite normal if you draw the maximum permitted C rating of the pack. Having experience in LiPo packs has shown that if the discharge current is over 50% of the maximum C rating they will swell and get very hot. I am sure that these issues were considered in Mr B's design, at the same the start upn surge current from any motor whether AC or DC is considerably more than the constant current and this is not going to help these packs survive a sensible reliable life if it is greater than the rated pack C. The pack also loses its storage capacity over time if this continually done.
One hopes that Mr. B has done all the calculations and checks on the discharge of the battery packs. |
@Hi_Tech
All I can contribute wrt your questions is that more than 100 Batteries were replaced, whereby one may speculate that it was bound to happen. The only hint of progress on Primary failures was today when anomalies were found by JTSB in ANA APU battery. (#729) @ITman My estimate for max charge current is 0.7C and for max discharge current 4C in case of APU battery and 2C in case of Main battery. These LiCoO2 cells are de-rated to 4.025V, and should not show any anomalies after a few months / a few hundred flight hours. Edit: Peak currents are a lesser concern these days as all heavy loads are inverter driven, and that with soft start, without which, an inverter driving a variable frequency load, such as a starter generator, would not survive. |
Here is the language from THE FEDERAL REGISTER....
. To address these concerns, these special conditions adopt the following requirements: Those sections of 14 CFR 25.1353 that are applicable to lithium ion batteries. The flammable fluid fire protection requirements of 14 CFR 25.863. In the past, this rule was not applied to batteries of transport category airplanes, since the electrolytes used in lead-acid and nickel-cadmium batteries are not flammable. The aircraft uses flammable electrolyte, it would seem the rule applies. So, what is the requirement....? Title 14: Aeronautics and Space CHAPTER I: FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION SUBCHAPTER C: AIRCRAFT PART 25: AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Subpart D: Design and Construction : Fire Protection 25.863 - Flammable fluid fire protection. (a) In each area where flammable fluids or vapors might escape by leakage of a fluid system, there must be means to minimize the probability of ignition of the fluids and vapors, and the resultant hazards if ignition does occur. (b) Compliance with paragraph (a) of this section must be shown by analysis or tests, and the following factors must be considered: (1) Possible sources and paths of fluid leakage, and means of detecting leakage. (2) Flammability characteristics of fluids, including effects of any combustible or absorbing materials. (3) Possible ignition sources, including electrical faults, overheating of equipment, and malfunctioning of protective devices. (4) Means available for controlling or extinguishing a fire, such as stopping flow of fluids, shutting down equipment, fireproof containment, or use of extinguishing agents. (5) Ability of airplane components that are critical to safety of flight to withstand fire and heat. (c) If action by the flight crew is required to prevent or counteract a fluid fire (e.g., equipment shutdown or actuation of a fire extinguisher) quick acting means must be provided to alert the crew. (d) Each area where flammable fluids or vapors might escape by leakage of a fluid system must be identified and defined. [Amdt. 25-23, 35 FR 5676, Apr. 8, 1970, as amended by Amdt. 25-46, 43 FR 50597, Oct. 30, 1978] |
RR NDB,
Here is my suggestion, from a completely different engineering point of view.... In the re-design, go back from 32V to 24V.. the would allow the room for round cells, and some space between them, in the same box. This would also negate the need for the stepdown transformers for the voltage.... |
The 787 uses starter generators for engine start, not pneumatic starters like other Boeings.
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