It's pretty clear now that lithium batteries are molotov cocktails waiting to light off. The anode and the cathode are separated by merely a sheet of plastic. Any flaw, crack, or pin hole in the plastic and the electrodes touch, a dead short, and they get hot. The lithium melts at only 350 some degrees, and molten lithium is as reactive as sodium. Sodium is so reactive that it will burn underwater.
So what to do? In the real world, the fix is straightforward, replace the lithium batteries with Nicads or nickel metal hydride, or even plain old lead acid. And replace the battery charging unit with one designed for the new battery chemistry. A few days of design work, run off some CAD drawings, write up change instructions, email them out to the field.
In the FAA and airline world, nothing is that simple. At a guess, the FAA paperwork, reviews, design studies, test procedures, parts lists, and plain old stuff, could take half a year. Leaving the 787's,. Boeing's world beating new product, grounded for half a year. It's already years behind schedule, and another 6 months delay might be more than Boeing and Boeing's customers can stand. Watch for cancellations in Boeing's 800 airplane backlog. And watch for new orders for the Airbus 350, which competes with the 787 even thought it hasn't flown yet.
Clearly FAA is hoping that something will turn up that will allow the 787 to keep flying with the existing lithium batteries. Could be anything, a defect in the battery charger, a manufacturing flaw at the battery maker, an extra inspection every flight, some extra insulation installed somewhere, anything. Otherwise, FAA will be under intense pressure to get the paperwork done and let the plane fly again. FAA (any any other bureaucrats) hate that. Plus remember that FAA is the outfit that OK'ed use of the lithium batteries in the first place, and nobody likes to admit they made a mistake.
2 comments:
My problem with the whole "it's the Li-Ion batteries at fault" issue is that there has been little in the way of details.
What kind of Li-Ion technology was used - LiMgO2 or LiFeO4 chemistries? (I doubt they used LiCoO as it's too unstable.)Did the batteries include some kind of temperature control (heating/cooling) as they do have a relatively narrow discharge/charge temperature range? Did they properly limit the charge rate to 0.7C which gives the maximum possible cycle lifetimes while subjecting the cells to minimal 'stress'?
All of these issues need to be addressed as I doubt it was the mechanics of the cells themselves that caused the issues. The level of testing to which the cells are subjected are mind-boggling. Unless Boeing used some no-name cheap knockoffs (highly unlikely), I doubt it was the cells.
Could be. But lithium batteries have burst into flames inside laptop computers, Chevy Volts, and while in transit aboard cargo aircraft. It's a bad history.
Neither Aviation Week nor the Wall St Journal has mentioned specific battery chemistry, they just say lithium or lithium ion. Little has been said about the charging circuitry, but I cannot imagine that it wasn't state of the art and monitored every battery parameter and followed the manufacturer's recommended charging cycle. Of course, despite all sorts of clever electrical design, the charger could have suffered electronic failure and overcharged the batteries. The battery maker was Yuasa in Japan.
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