New Boeing 787 Dreamliner Battery Incident - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: January 15, 2014, 09:24:12 pm
content: More problems:http://www.reuters.com/article/2014/01/15/us-japanairlines-787-battery-idUSBREA0E0O020140115

author: Phaedrus
author_rank: Frequent Contributor
timestamp: January 15, 2014, 09:30:24 pm
content: What is this battery made of, gasoline and tinder?There's Li-ion battery flammability, and then there's this...

author: rdl
author_rank: Super Contributor
timestamp: January 15, 2014, 10:01:06 pm
content: Apparently they only improved the containment system, but never really fixed the actual battery problem?

author: digsys
author_rank: Unknown
timestamp: January 15, 2014, 10:03:30 pm
content: Tesla DID offer to fix it for them !! Events like these, out of arrogance or stupidity, just give EVs "bad" points.

author: rolandpenplotter
author_rank: Regular Contributor
timestamp: January 15, 2014, 10:04:13 pm
content: I thought aeroplanes ran on jet fuel...

author: johnboxall
author_rank: Unknown
timestamp: January 15, 2014, 10:08:00 pm
content: Quote from: rdl on January 15, 2014, 10:01:06 pmYeah, a really thick metal box with external ventilation -http://www.boeing.com/787-media-resource/docs/787-battery-certification.pdf

author: tom66
author_rank: Super Contributor
timestamp: January 16, 2014, 12:25:43 am
content: Boeing should use NiMH in an application this critical. I don't want to be on a plane which has a generator failure only to find that battery is the last line of power for instrumentation, and has just died.

author: TerraHertz
author_rank: Super Contributor
timestamp: January 16, 2014, 12:38:33 am
content: Quote from: tom66 on January 16, 2014, 12:25:43 amBoeing should talk with TEPCO. They're the experts in PR obfuscation when dealing with power system melt downs.Because never mind the potential for catastrophe, it's public face that matters most.Oh wait...

author: EEVblog
author_rank: Unknown
timestamp: January 16, 2014, 12:45:26 am
content: Quote from: tronixstuff on January 15, 2014, 10:08:00 pmHey, that dude with the cool moustache looks like he knows what he's doing, she'll be right.

author: staxquad
author_rank: Frequent Contributor
timestamp: January 16, 2014, 07:41:29 am
content: Quote from: tom66 on January 16, 2014, 12:25:43 amThe Yuasa LiIon used by the 787 can recharge at a 1C rate (recharge at a rate of 65 amps for one hour), discharge at a 5C rate and has a 65Ah capacity.Boeing designed the 787 around the current draw, weight, size and recharge time of the LVP-65 LiIon batteries.(edit requested by johansen: the LVP-65 LiIon batteries fit the requirement for the current draw, weight, size and recharge time required by the Boeing 787)If a match is required for a current draw of 150A (for airplane powerup), they would need 9x the batteries used by the 777, with a resulting weight of 436kg compared to 28kg.Other batteries do not fit into the 787's current design.

author: hiddensoul
author_rank: Regular Contributor
timestamp: January 16, 2014, 07:44:19 am
content: Quote from: tom66 on January 16, 2014, 12:25:43 amIt is much worse then instrumentation.... Think control as well as the dreamliner is fly by wire so a complete power fail means no control of the control surfaces of the plane, ailerons Rudder etc

author: EEVblog
author_rank: Unknown
timestamp: January 16, 2014, 07:48:22 am
content: Quote from: staxquad on January 16, 2014, 07:41:29 amI can understand the weight optimisation here, but looking at the big picture, that's less than 5 average passengers and their baggage.

author: hiddensoul
author_rank: Regular Contributor
timestamp: January 16, 2014, 08:01:20 am
content: Quote from: EEVblog on January 16, 2014, 07:48:22 amYeah true and if the dreamliner is anything like the 747 there is a huge weight in the tail to balance the aircraft. In the case of a 747 it is depleted Uraniumhttp://en.wikipedia.org/wiki/Depleted_uranium#Trim_weights_in_aircraft

author: Rerouter
author_rank: Super Contributor
timestamp: January 16, 2014, 09:53:19 am
content: From a quick glance, wouldn't external ventilation expose the battery the wider temperature and pressure swings than what it was experiencing inside the cabin? thus increasing the rate of failure.

author: Psi
author_rank: Super Contributor
timestamp: January 16, 2014, 09:57:24 am
content: I bet if you turn over one of their lipo cells you will find the word "Turnigy"

author: BravoV
author_rank: Super Contributor
timestamp: January 16, 2014, 10:09:01 am
content: Quote from: Psi on January 16, 2014, 09:57:24 amNope ... there is no "fire" word in there, must be using those xxxx-"FIRE" cells similar to these ...

author: Psi
author_rank: Super Contributor
timestamp: January 16, 2014, 10:30:13 am
content: SURE-FIRE is the funniest name ive seen on those AA style lipos.

author: Wytnucls
author_rank: Super Contributor
timestamp: January 16, 2014, 11:00:40 am
content: Quote from: EEVblog on January 16, 2014, 07:48:22 amThere is no way the aircraft draws 150A from the batteries for ground operation. In fact, the batteries are never connected to the system in normal operation, except for intermittent charging and aircraft braking.If external power is not available for aircraft APU (auxiliary power unit) start, it can be started from a dedicated APU battery, while the aircraft main batteries power a minimum of instruments to monitor APU start. Once the APU is on line, the batteries are automatically removed from the network.In an emergency, if all 6 generators are offline, the RAT (Ram Air Turbine) will deploy, providing electricity and hydraulic pressure to the aircraft. if that fails, the batteries should provide power to the emergency busses, for about 30 minutes of flight.AFAIK, there is no balancing weight in the tail of the 787. Every kilogram matters in aviation these days. Even the aircraft water tank quantity is now optimized, depending on flight time. On the Airbus A340 and A330, extra fuel tanks are installed in the horizontal stabilizer.

author: johansen
author_rank: Super Contributor
timestamp: January 16, 2014, 11:13:14 am
content: Quote from: staxquad on January 16, 2014, 07:41:29 am1C charge rates on ni-mh simply aren't possible, because the battery is only 66% efficient on cell recharge.they are however possible with nickel cadmium, and it will maintain 80% charge efficiency.so you would be looking at a 5 fold weight increase for ni-cd, but not nimh (3 fold perhaps, but it can't handle the power without an active cooling system.)for the amount of trouble this battery has caused boeing, they could have installed nickel-hydrogen cells...also, who told you Boeing designed the airplane around a 28 kilogram battery?

author: tom66
author_rank: Super Contributor
timestamp: January 16, 2014, 11:18:22 am
content: Most consumer NiMH can charge and discharge at 2C. I'm pretty sure the Prius battery, rated at 201V 6.5Ah, and 30kW continuous discharge, is modified NiMH technology:http://en.wikipedia.org/wiki/Toyota_Prius#Batteriesi.e. ~23C discharge.Yes a NiMH would weigh more but it would be much safer.In an EV, LiIon is acceptable, because in the absolute worst case, you get a slow burning battery fire the passengers can escape from.In a plane, you don't have that luxury.

author: Corporate666
author_rank: Unknown
timestamp: January 16, 2014, 02:06:53 pm
content: Quote from: hiddensoul on January 16, 2014, 07:44:19 amBut there are numerous backup systems - like quadruple redundancy - to prevent that from ever happening. One could also say "in a 747, a complete engine failure means you can't do anything". You can't safeguard against any possible eventuality, but the 787 is very, very good in terms of electrical redundancy.

author: Corporate666
author_rank: Unknown
timestamp: January 16, 2014, 02:22:14 pm
content: Quote from: EEVblog on January 16, 2014, 07:48:22 amIf they change the batteries substantially (like to a completely different type/chemistry/topology), it would mean major engineering changes to the aircraft costing hundreds of millions, as well as re-certifying the aircraft costing as much or more, and delaying any deliveries for probably a year or more.It would be like changing the engine of a car from electric back to gasoline after a few electric fires occurred... not feasible.Every problem/failure on an aircraft is measured in likelihood per mile flown. Something might be "once per 100,000 miles" or "once per million miles", etc. The probability of anything happening is never zero, so even something like "structural failure of wing causing total loss of control" isn't something that can never happen, just rated by the likelihood.Same with the batteries failing or catching fire. People are looking for "never", which is a term that won't ever apply to aircraft systems. The problem wasn't so much that a battery failed, but that it happened much more frequently (by orders of magnitude) than it was supposed to.I think Boeing did the right thing... they saw an unexpectedly high failure rate, so they re-designed the system such that these failures are no longer threatening to the safety of the aircraft. The battery that just popped at Narita worked as intended. The overpressure valve opened and the liquid released was contained in the spill mechanism, and the gases were vented out the designated port. Whatever happened inside the battery remained contained by the containment box and didn't spread or cause a fire or cause any collateral damage.I think it is a bit strange that of the three 787 battery incidents, they are all with two airlines out of sixteen who have 787's, and both with Japanese carriers. There are about 120 of these aircraft in daily service right now and it's curious that the failures seem limited to a select few with the same carriers in the same country.

author: hiddensoul
author_rank: Regular Contributor
timestamp: January 16, 2014, 02:29:01 pm
content: Quote from: Corporate666 on January 16, 2014, 02:06:53 pmThe 747 still has physical steel cables (Non Electrical) that can pull on the control services with a real yoke and rudder pedals pulling those cables, yes they are power assisted but in a complete failure the vertical speed indicator, airspeed indicator, artificial horizon and VERY heavy manual flight controls all still work

author: SeanB
author_rank: Super Contributor
timestamp: January 16, 2014, 06:42:56 pm
content: At a wild guess the Japanese planes are higher along the take off/landing cycle curve than the other planes. doing mostly short haul flights from one end to the other, with the odd regular long multi hour flight as well to hold the cells at high altitude and low pressure for hours, making any marginal seals very stresses from both high pressure and cycling. Thus these are failing faster than the rest just from cycling.

author: staxquad
author_rank: Frequent Contributor
timestamp: January 16, 2014, 07:20:10 pm
content: Quote from: mojo-chan on January 16, 2014, 02:38:47 pmThey added insulation between each battery in last year's fix. Insulation isn't conducive to cooling. If they wanted to isolate the batteries, make a square donut enclosure and have the batteries single file inside the enclosure so the sides and center ventilates and one battery doesn't heat up the others.And surely they're accumulating DATA on EACH CELL while in use and during recharge to figure this out (logging the temperature, voltage, current draw, internal resistance ofeach cellover time, with an alarm when a parameter is out of whack).As for their problem, I would venture to guess it's the high current draw and subsequent fast recharge over time that unbalances the cells and their balancing circuitry can't handle the large discrepancies in voltage, so they end up with cells that go too low in voltage when in use and too high in voltage in recharge if they are testing the voltage in aggregate. I've got a $2 alarm that fits into the balance plug of a pack that displays the voltage of each cell and goes off when just one cell reaches 3.3V or whatever minimum I want to set it at. But surely Boeing checks individual cell voltages for high and lows and not the aggregate when in use and while recharging (my charger never goes past the set voltage, like 4.2V, even if the other cells are way less if irreversibly damaged. After recharging each and every battery, I always check each cell voltage and each cell impedance for battery health, so it's dumbfounding how Boeing can have their ongoing battery problem if they are logging relevant data on each and every cell and flagging bad packs for maintenance from the data).If the problem is the load, double the battery pack to lessen the load on the cells.(others have mentioned load spikes as the probable cause; well Boeing, log the data and find out)$1.88 shipped

author: RobinM
author_rank: Newbie
timestamp: January 16, 2014, 07:26:14 pm
content: Quote from: hiddensoul on January 16, 2014, 08:01:20 amThose trim weights aren't to balance the overall weight of the aircraft, but to counterbalance the weight of moving control surfaces. Seethis articlefor a brief description. Aircraft designers have always been militant about weight reduction, and deal with static balance issues by means other than huge weights.

author: Corporate666
author_rank: Unknown
timestamp: January 16, 2014, 10:41:07 pm
content: Quote from: hiddensoul on January 16, 2014, 02:29:01 pmBut then if the rudder falls off, it doesn't matter if there are steel cables in addition to the electrical actuation.The point I was trying to get at is that people worry about the electrical nature of the 787. But designs, especially commercial aircraft, are always done to a failure rate. If you have three redundant control systems that have a failure rate individually of 1 in 1,000,000 flight hours each, and a control surface that has a failure rate of 1 in 100,000 hours... then it doesn't matter if you have a 4th and 5th redundant system on the control system, and spending time and money developing such would be foolish.On the 787, it has 3 redundant systems and no single points of failure. "Complete electrical failure" is another way of saying "three redundant non-interconnected systems all failing individually at the same time", which is not more likely than all three separate and individual control systems on a 747 failing together. It's statistically virtually impossible unless there was major damage to the aircraft (hit something mid-flight, wing fell off, etc type stuff) - and in those situations, additional redundant systems would fail also.

author: hiddensoul
author_rank: Regular Contributor
timestamp: January 17, 2014, 07:00:14 am
content: Quote from: RobinM on January 16, 2014, 07:26:14 pmYes Wytnucls, already commented to that effect earlier in the thread

author: amyk
author_rank: Super Contributor
timestamp: January 17, 2014, 11:56:36 am
content: It has occurred to me that the protection requirements have a very different characteristic in this application compared to e.g. a consumer device like a laptop, mobile, tablet, etc.In the latter, the priority is to stop a cell from venting/catching fire, even if it means cutting out the power from it.In the former, the priority is to keep the power available, even if it means the cell will be discharged to the point of being damaged, or discharged fast enough to cause it to vent or catch fire, and so it may make more sense to contain a fire if it does occur than to allow it to cut off power.

author: tom66
author_rank: Super Contributor
timestamp: January 17, 2014, 12:05:50 pm
content: From my experience at the point of venting a li-ion polymer cell has nearly zero volts across it. Li-ion may behave differently.

author: cimmo
author_rank: Frequent Contributor
timestamp: January 17, 2014, 02:30:30 pm
content: Quote from: hiddensoul on January 16, 2014, 02:29:01 pmYes, the 747 does have direct mechanical connection to the flight control actuators. But these actuators are hydraulically powered with NO manual reversion. Loose the hydraulics, loose the aircraft. The DC10 has similar topology (but only 3 hydraulic systems) and once, due to an uncontained engine failure that severed all three system hydraulic lines that were stupidly routed close together, all the fluid was lost and the aircraft was almost unflyable, differential engine power got them almost to a landing; Google United 232.FWIW, the DC10 had a lot of 'gotcha' design defects in the systems, responsible for several major accidents. Due to the merger of Mcdonnell Douglas and Boeing, it would seem that the McDD system design philosophy is now taking root at Boeing.Over the years several airliners have lost power from ALL engines (including APU) and still remained flyable (gliding) due to the necessary systems (hydraulic and electric) being powered from a Ram Air Turbine (RAT), a little propeller driven pump/generator that pops out into the airflow.FWIW, even though the 787 is very heavily dependent on the electrical system (1400 kVa of generators but no engine bleed air), there are still engine driven hydraulic pumps on each engine and one on the RAT. The engines have their own dedicated generator for their control units and the standby instruments have their own batteries, so even if the main busses fail the aircraft should be landable (soon).Having said that, IMHO the choice of battery chemistry was a mistake. Plenty of recent airliners are very electrically intensive, but they don't use LiCo. If Boeing had any sense, rather than make a bomb proof box for the existing batteries, they should have changed over to LiFePO. Airbus have even decided to revert to NiCd for the new A350.

author: cimmo
author_rank: Frequent Contributor
timestamp: January 17, 2014, 02:56:56 pm
content: Quote from: staxquad on January 16, 2014, 07:20:10 pmIt should be noted that the 787 has TWO basically identical batteries. One forward (main) and one aft (APU), only the aft battery is likely to be exposed to any serious discharge currents as it is used to start the APU when no ground power is available. The forward battery is purely a backup for inflight generating failures (and powers the brakes and lights while under tow on the ground).The forward battery has the easier life of the two as far as discharge currents are involved, and yet of the three battery 'thermal events' (as the PR people like to call them), two of them (including the most recent) have involved the forward (main) battery.

author: SeanB
author_rank: Super Contributor
timestamp: January 18, 2014, 07:30:21 am
content: At a guess the aft battery having a regular high current test ( APU start) quickly weeds out the failing units as a failure imminent warning while the front one will slowly degrade. I agree a different battery chemistry would be better, along with better monitoring systems.

author: Wytnucls
author_rank: Super Contributor
timestamp: January 18, 2014, 09:06:54 am
content: APU start is seldom done on batteries. APU usage is confined to the bare minimum, because it gobbles precious fuel and also because of noise considerations at most airports. 99% of the time, APU start will be done with ground power connected to the aircraft. I'm not familiar with the intricacies of the 787 electrical system, but it would be surprising if the APU battery is used for APU start, when an alternate power source is available.

author: staxquad
author_rank: Frequent Contributor
timestamp: January 18, 2014, 06:24:55 pm
content: from Boeing (the how and why):http://787updates.newairplane.com/787-Electrical-Systems/Batteries-and-Advanced-AirplanesBatteries and Advanced AirplanesElectricity has been used in powered flight since the pioneering days of aviation. Orville and Wilbur Wright used an electrical spark to ignite the fuel mixture in the engine that powered the Wright Flyer off the ground and into the history books. Today’s jet airplanes have much more demanding requirements and consequently more advanced electrical systems, of which batteries are an integral component.The 787 Dreamliner has two primary rechargeable batteries – the main and auxiliary power unit (APU). While identical part numbers, they serve separate purposes.The main battery “powers up” aircraft systems, bringing the airplane to life before the engines have been started.Once the engines are started, the electrical energy to run the systems comes from generators.It also is used to support ground operations such as refueling and powering the braking system when the airplane is towed. The main battery also provides backup power for critical systems during flight in the extremely unlikely event of a power failure.It is located in the forward electronics equipment (EE) bay, which is under the main cabin floor at the front of the airplane.The APU battery supplies power to start the APU, which in turn can start the airplane engines. The APU, and its battery, also serves as part of the multiple layers of redundancy that would ensure power in the rare possibility of a loss of primary sources of power.Matching the right battery to the requirementsAfter 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.Batteries, like other technologies, have advanced significantly, and lithium-ion type batteries match up with the unique requirements of advanced aircraft.Lithium-ion batteries have other key advantages that suit it for modern jet application:The required high voltage and high current productionImproved power qualityAn ability to recharge quicklySimilar functionality to that of NiCd batteries while weighing 30 percent lessCompact – about the size of the average car batterySince 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.Boeing has been using lithium batteries for decades safely and successfully in other demanding aerospace applications. For instance, they have been successfully used in the satellite industry.Closer to home, lithium batteries are being used safely to power everything from consumer electronics, household power tools and many other applications.Boeing design philosophyBehind the selection of any individual component is a deep commitment and philosophy about airplane design. Boeing designs airplanes with two key objectives in mind: design to prevent failures, and design in protections in case they do. Above all, the goal is to ensure that no single failure will ever prevent safe operation of the aircraft. This philosophy is integral to the battery design, which includes multiple independent protections to the battery.Aviation pioneers Orville and Wilbur Wright had a mission: Fly forward for as long as possible, maintain speed, land at a point at least as high as the takeoff point and carry one pilot. In December 1903, the Wrights did just that, flying 852 feet (260 m) in 59 seconds.Today, expectations are much higher. For example, as the world’s most advanced family of jetliners, the 787 Dreamliner is designed to carry as many as 290 passengers as far as 8,500 nautical miles (15,750 km) — a third of the way around the Earth.So it’s no surprise that to meet today’s missions, airplane electrical systems have been transformed from the single electric spark the Wright Brothers needed to the highly engineered, redundant systems that make modern jet travel possible.Airplane power basicsOn an airplane, the electrical system produces, controls and distributes power to all the other systems that need it — flight deck displays, flight controls, in-flight entertainment and more. It’s much like the electrical system in your house, which carries electricity throughout the rooms to power your lights, television and so forth.Unlike your house, though, the airplane generates electricity as it flies. Airplanes don’t fly on battery power. Generators on the engines make power in flight.The traditional airplane: electrical and pneumatic systemsOn a traditional airplane, power is extracted from the engines in two ways to power other airplane systems:Generators driven by the engines create electricity.A pneumatic system “bleeds” air off the engines to power other systems (e.g., hydraulics).Modern jet engines are very efficient, but removing that high-energy air robs them of some energy. A pneumatic system means that the engines produce less thrust, so they must be bigger, work harder and use more fuel. The system also means more weight, fuel burn and maintenance due to the heavy ducts and equipment needed to manage that hot air.The 787: A more-electric systemThe 787 Dreamliner uses more electricity, instead of pneumatics, to power airplane systems such as hydraulics, engine start and wing ice protection. Benefits of the 787’s innovative, more-electric design include:More efficient power generation, distribution and use — including new remote power distribution units, which reduce wiring and save weight (approximately 20 miles, or 32 km, less wiring than on the 767).Better fuel efficiency — better for airlines and the environment.Lower maintenance costs and fewer maintenance tasks.Less drag and noise.Because the 787 uses more electricity than do other Boeing airplanes, the 787 generates more electricity, via six generators: two on each engine and two on the auxiliary power unit (APU, a small turbine engine in the tail).On the ground, the 787 can be started without any ground power: The APU battery starts the APU generators, which start the APU to power the engine generators, which then start the engines.In flight, the four engine generators are the primary sources of electrical power; the APU generators are secondary. Power runs from the generators to four alternating current (AC) buses, where it is either distributed for use as is (235 V AC) or converted to what other systems need.Other power sources for the 787 includethe main battery, used primarily for brief ground operations and braking; the APU battery, which helps start the APU;and ground power, which can connect through three power receptacles. The main battery, APU battery and ram air turbine also are available as backup power in flight in the unlikely event of a power failure.As with every Boeing airplane, the 787 includes many layers of redundancy for continued safe operation, and the electrical system is no exception. For example, Boeing has demonstrated that the 787 can fly for more than 330 minutes on only one engine and one of the six generators and land safely.Safety is designed inThe Boeing Company works to a specific design philosophy so that designs meet or exceed federal regulations.Boeing designs to preclude failure — that is, so that systems won’t fail. Then Boeing goes further, assuming failure will occur and designing for the proper protections. Boeing also designs so that no single failure will cause an accident; for example, by including redundant systems, separating systems in space and functions — so that the loss of one doesn’t cause the loss of another — and providing standby and protective systems.The 787 completed 5,000 hours of flight testing and an equal amount of test time on the ground. That testing demonstrated that the airplane performs as designed. The 787 successfully completed the Boeing program to test and validate the design as well as the most robust certification program ever conducted by the U.S. Federal Aviation Administration. The 787 electrical system was certified along with the airplane on Aug. 26, 2011.

author: cosmos
author_rank: Regular Contributor
timestamp: January 18, 2014, 07:03:52 pm
content: Quote from: amyk on January 17, 2014, 11:56:36 amThis hits the nail on the head.The trick is then of course to not continue operating (take off again) after the system has been compromised, it needs to be replaced and entering the unsafe state (become airborn) again should be blocked until this has happened ...Safety in planes have an interesting duality, (simplifying a bit to make a point here, and it is not only about the batteries)on the ground you want to be paranoid and detect faults and block operation so you do not take off with known faulty systems, once in the air you suddenly only want best effort...just keep it flying.With redundant systems you look for common failure mechanism, in IEC61508 this is expressed as the beta factor.Beta factor depends on how unrelated the redundant functions are... from 30% down to 1% in most cases where 1% is hard to reach.If you have two redundant functions each with 1000 faults per 1e9 hours, the result of a 5% beta means the combined fault rate is 50 per 1e9 h (only a 20x factor improvement over having 1 function).