I’ve been pretty quiet about the 787 as airplanes continue to sit on the ground, collecting dust, waiting for a fix to that nasty “battery catching on fire” problem. It’s primarily because I didn’t have much to add to the discussion. But now that we have a fix, I thought I’d put a post together.
As we all know by now, the Boeing 787 has been more Nightmareliner than Dreamliner these last few weeks. For over two months, the 787 has been grounded because of problems with batteries.
The issue at hand is not necessarily a huge surprise. Historically, airplanes have used batteries to power a variety of systems, but they’ve used older technology batteries. In the 787, Boeing decided to get fancy and use lithium ion batteries because it was relying on batteries to power much more than in previous airplanes. And lithium ion sounded like the best answer.
There’s a good news/bad news situation with those batteries. First, they are awesome at providing power. Boeing chose them because they can pack a ton of power into a small space, and space is at a premium on airplanes. This is particularly important on the 787 where more battery is needed in general.
The bad news? They like to catch on fire. Seriously, they’re not the most stable things around, and that’s why there are even restrictions on bringing spare batteries in your luggage. (You can’t.)
Think this isn’t a big deal? It is. It’s suspected that a UPS 747 was brought down by a lithium ion battery fire, though that hasn’t been made official. But there have been other accidents as well and it’s a huge concern.
Right now, you might be thinking Boeing is insane for trying to put lithium ion batteries on the 787, but that’s not really the case. Boeing knows the dangers involved in using those batteries, and it prepared a system that it thought would be adequate to mitigate the risk to a level where it wouldn’t be an issue. Apparently the government agreed when it signed off on the aircraft. If there’s one thing the government needs to do well, it’s regulate safety issues. Oops.
That didn’t work out so well. We know that there have been multiple battery-related fires on the 787 and it was so concerning that the airplane was grounded worldwide until a fix could be put out. Blame certainly lies both on Boeing, on its suppliers, and on regulatory bodies, but that doesn’t matter. We just needed a fix. In particular, Japanese airlines ANA an JAL really needed a fix since they had taken delivery of so many of the early airplanes.
Now, it looks like we have a fix from Boeing. Here is what’s happening.
- Better quality control procedures and testing to make the battery so that it behaves as it should
- Reducing the level considered to be a full charge and raising the level at which recharging begins
- Additional insulation between battery cells and between the battery and battery case to prevent fires from spreading
- New wiring and wire-sleeving inside the battery that will be more heat and chafing-resistant
- New fasteners that connect the metallic bars between cells that will have a locking mechanism
- Changes to the battery case that will now allow for better heat-venting and moisture-draining
- The battery case will now sit in a new enclosure that will isolate the battery further and provide direct venting outside the aircraft. This enclosure will deprive the battery of oxygen and will prevent a fire in the enclosure.
That’s a lot. So is this overkill? Probably, and I’m glad. The point here is to reduce the chance the battery will explode into a ball of fire, and then if it somehow does, reduce the chance that the fire can damage the airplane. I want this thing to be overbuilt because we don’t really know everything about lithium ion batteries and how they’ll behave in all situations. This is probably more than needs to be done, but that’s good. Load it up, make it safe. People are going to be watching closely.
Now the hard part is waiting… going through the testing process so that the 787 can fly again. As someone with no engineering background, this looks like a really solid solution, but what the heck do I know? Now it’s up to the authorities to do some serious testing. And you know that they will be looking at this VERY closely this time. According to Boeing, it’s just a matter of weeks before this is up and running. I just wonder how many weeks we’re talking about here.
I also find myself wondering how much more this new enclosure will weigh, and how much will it hurt the aircraft’s performance? At this point, that’s a secondary concern, but airlines are not going to be happy if it cuts range too much. On the other hand, Boeing just needs to get this thing back in the air again. And when that happens, I’ll gladly fly one.
It seems like a reasonable solution, but short of the “1000% Confidence” the government spoke of for knowing why the problem happened and ensuring it will never happen again.
I hope the plane gets in the air quickly, even at reduced ETOPS to give carriers the capacity back and get some cycles/hours in for data collection
Several Points. I think it is a safe bet that the modifications will add less weight than the switch back to Nickel-Cadmium (NiCd) battery technology. The weight savings was originally about 60 pounds. That’s the good news.
The bad news is that I am no longer convinced that Li-Ion cells are a good fit for long haul aircraft. While they have very attractive energy density relative to NiCd’s, by comparison, they are very ‘delicate’. NiCd technology tolerates what most would regard as extreme abuse without batting an eye lash. For example on a Beechcraft King Air, a 24V/45Ah NiCd has to put out about 1000 amps (same as required to turn over the 787’s APU) to spin up the PT6 engine. Fortunately you don’t have to provide 1000 amps for very long. The faster the starter spins, the less current is required (that’s a basic fact of DC Motors). Once the first PT6 is started, the battery is then recharged at 200-300 amps for a few minutes, and then it repeats the process with the other PT6 engine.
The reality is you can discharge a NiCd to zero volts, and as long as you don’t ‘reverse charge’ the NiCd cell, it will not be damaged. At the other end, these cells tolerate overcharing quite well, in fact most NiCd’s can be recharged almost indefinitely as long as the charge rate doesn’t exceed 10% of the Amp Hour rating. By contrast both over discharging and overcharging cause VERY BAD things to happen to Li-Ion cells.
As far as the impact on range, the additional 60 pounds wouldn’t be easily measured. It is on the order of 1 mile. There is more variation than that in the OEW of individual aircraft and the Specific Fuel Consumption (SFC) of the engines.
In terms of cost. That can be thumbnailed. If you assume the aircraft is operated on average 12 hours per day, and has a 20 year life you can estimate the extra fuel burn. If you assume L/D (Lift divided by Drag) is 17, and the Specific Fuel Consumption on the engines at cruise is about .48 . So you can calculate the fuel burn:
60/17=3.52, so the extra weight will require 3.52 pound extra thrust to carry.
3.52 x .48= 1.69 pounds of fuel burned per hour for the extra weight
20.28 pounds per day
7402 pounds per year
148,000 pounds over the life of the aircraft.
67,280 Kilograms, which is about 81,000 liters or about 21,430 gallons
If you assume an average cost of Jet-A/A1 to be about $4/gallon, the total
cost over the life of the Aircraft is about $85,700.
It just isn’t big money, and in fact if the life of the Li-Ion cell is substantially shorter than NiCd, much of the savings will be eaten up by the cost of battery replacement and labor required. As airplane parts go NiCd batteries are relatively inexpensive. However in the airline business, the margins are so thin that they worry about every cent.
If this is the case why is Boeing dead set on keeping Li-Ion in the 787?
Will there be an airline driven mod to put a NiCd battery into the 787 in place of the Li-Ion one?
Agreed. If this is the case, a few weeks out of service eats all the benefit. Though you haven’t spoken about size differences. As I understand it, the NiCd batteries would take a lot more space, but I don’t know in context how much space that would be
I remember reading that Airbus has recently decided to go with Nickel Cadmium batteries on the A350, in part because of its problems on the 787.
Edit: Should read because of the lithium ion bettery problems on the 787.
You are right DesertGhost!!!
I think so….
Smokey the Bear just doesn’t look the same like he did when I was a kid….lol
Amazing how before the 787’s rolled off the assembly line people were worried about it being made from so much plastic, but it’s a battery that is causing problems.
At least this planes problems were caught before any accidents and is being addressed before they fly again. The DC10’s problems caused hundreds of lives, but that airplane went on to have a long history. The 787 will rise again and have a long history I’m sure.
Another person commented that the cell life of Li-ion is shorter than NiCad. Actually the projected battery life for Li-ion is double that of the NiCad.
NiCad batteries have had their issues too. I have personally seen two separate NiCad installations that exhibited a “China Syndrome” (they burned through the hull of the aircraft) after they exhibited thermal runaways.
Another important design characteristic of the Li-Ion battery is the high conductance (very low internal resistance). This allows the battery to provide very high currents without experience the voltage drop that you see with other battery types.
I am not confident that the root problem is “solved” (was a root cause determined?). However, it appears that Boeing is implementing a design solution that will help prevent cascading thermal runaways within the battery, and providing a means to this type of battery failure from affecting other systems or aircraft structure.
I do think that the root cause of the problems is the choice for the Li-ion chemistry variant that provides the best power densities, at the cost of being the most sensitive to thermal runaway. And to get the best performance requires tight mechanical tolerances during manufacturing of the cells. A tiny manufacturing defect may grow into an electrical short and trigger the thermal runaway.
I predict that the battery enclosure will be the best risk-reducing measure of the batch that Boeing presents and that 787 battery overheats will remain regular events.
Elon Musk was right! http://www.forbes.com/sites/businessaviation/2013/02/05/is-boeings-787-battery-design-flawed-ask-elon-musk/
Lithium based batteries certainly can be nasty little things. I was part of an unmanned aircraft competition in college. I’ll never forget the first year we competed, one of the other universities left their Lithium Ion batteries charging in their hotel room and went to dinner. They returned to find their hotel room, including their aircraft, going up in flames.
What bothers me is that the problem is chemistry related, not design related. Li-Ion isn’t stable at high altitude, it’s a proven fact. What’s even more alarming is that the compound can combust on its own with a minimal catalyst. But for reasons related to profit, engineers are putting a compound in an environment they know to be unstable for that compound with the justification that they can mitigate a volatile reaction by over-engineering the problem. It’s stupid. If you know a compound can combust on its own at high altitude, and you have a proven track record of that happening, don’t put it in an airplane.
Cranky there is a big catch 22 that you did not mention. Boeing is going to retest the 787 batteries using a standard it helped create but did not use on the 787. Sounds to me like someone overrode an engineer. How long till the emails leak?
I wonder if Airbus should put a new slogan on its airplanes. “Tested to a higher standard”
There is a long tradition of respect regarding safety issues in the airline business. When there is a crash all airlines pull their advertisements, not just the airline that suffered the crash.
I haven’t seen Boeing nor Airbus trash talk each other on safety, they both have enough courtsey not to do that.. (Now Branson at VA is a completely different ball of wax..)
Let’s hope the 787 battery fix is a good one. I read the FAA is furloughing all 2800 of their safety inspectors who, in the interest of public safety, are the professionals that are (were?) supposed to make sure it works during actual passenger operations – not just in a laboratory. Honestly, you can’t make this stuff up.
I don’t think your last bullet is correct: “This enclosure will deprive the battery of oxygen and will prevent a fire.”
Li-ion does not need an outside source of oxygen to burn.
Jeff, to be pedantic, a fire is an exothermic reaction of combustible matter with oxygen. The chemicals in a Li-ion can react exothermically without a supply of oxygen, creating all of the nasty aspects of a fire (heat and flames) while one of the mechanisms of extinguishing the fire is inoperative. This makes battery “fires” more nasty than an ordinary fire.
Jeff – Thanks. I updated the bullet point to use Boeing’s wording at the end – no fire in the enclosure. In other words, I assume that means that while the battery burns, nothing else will inside the enclosure because they can cut off the oxygen to limit the damage. At least, that’s how I’m interpreting what Boeing is saying.
There are a number of types of Li-ion batteries which have been in successful use for years. It appears that the particular type and design of the Boeing selection is the most likely to have a problem.
Leeham News quote
Special ?task force? studied lithium-ion batteries long before JAL 787 incident
March 13, 2013 31 comments
A special task force was studying issues relating to the use of lithium-ion batteries in airliners long before the January 2013 Japan Air Lines fire. The effort began in 2008 and it met in December 2012, one month before the JAL fire.
Boeing, the FAA, Embraer, Airbus, GS Yuasa, American Airlines and ALPA are just a few who participated in these meetings, according to documents.
Randy Tinseth, VP Marketing for Boeing, referred to the group when he discussed the FAA approval to proceed with the Boeing plan to fix the 787 battery issues in his blog, here.
The certification plan calls for a series of tests that show how the improved battery system will perform in normal and abnormal conditions. The test plans were written based on the FAA?s standards as well as applicable guidelines published by the Radio Technical Commission on Aeronautics (RTCA), an advisory committee that provides recommendations on ways to meet regulatory requirements. The RTCA guidelines were not available when the original 787 battery certification plan was developed.
We asked Boeing what the document was that Tinseth referred to above: it is a document numbered DO-311. There are a number of documents at RTCA containing the reference to DO-311.
DO-311 is described by RTCA as:
I would have loved to have been a fly on the wall during the battery discussions when they designed the plane. I can’t imagine it was a unanimous decision. I’m not sure if they thought they had no other reasonable options or someone presented a strong enough argument and persuaded most of the critics.
I would definitely avoid the aircraft. Not necessarily because I think a crash will occur but I do think further issues will occur and would rather not deal with flight delays/cancellations.
I’m not really sure how much stock I would put in the fact that the government signed off on the original design. Having had a lot of government experience the thought process the government gives items tend to vary greatly. Often with aircraft they tend to rely on Boeing/Airbus expertise IMO.
Good start, But Boeing and this article have missed a few things, firstly that Boeing understood this to be a problem dating back to 2010 and has been less than 100% with FAA and passengers, lets get all the data from Boeing everything from initial testing to maintenance records concerning the failed batteries. Next some core information about Li-Ion, how it functions and how other industry have overcome failings inherent in product, like simply adding a temperature gauge to the outside of the battery, if battery reaches a specific temperature, battery is cut off. Next Li-Ion has major issues with charging and ambient temperature, if environment where battery lives and is charged is above 77F overheating is morel likely to happen and charging current must be reduced , so compartment should be temperature controlled, monitored and tied into charging circuit . and the number one basic thing Boeing should be doing is to monitor the float current, if current goes above 3.27V then battery is being overcharged and meltdown is imminent.