Boeing made a bold move with the 787 Dreamliner. The aircraft was long overdue when it finally began flying last year, but it was not the victory Boeing was hoping for. From the outset there were issues with the plane’s lithium-ion batteries. After a series of fires, the FAA grounded all 787 until a fix could be found. As of Friday, the FAA certified Boeing’s proposed solution. The 787 is returning to the skies soon, but how was it done?Boeing will swear up and down that the battery issue was a minor one. However, the January action by the FAA marked the first time since 1979 that an entire fleet of planes was grounded — it was serious enough. Most aircraft rely on hydraulics or pneumatics to operate on-board systems, but the Dreamliner had a pair of big honking lithium-ion batteries instead. These cells were the focus of 300,000 hours of engineering time to come up with a fix.The old batteries were extremely prone to thermal runaway — a type of battery failure characterized by steadily increasing temperatures that eventually cause one or more cells to rupture and spill flammable materials (like lithium) into the battery’s internals. This usually leads to other cells being ruptured, and that’ll ruin your day.Boeing worked on the problem from three different angles. First, the cell and battery build process has been enhanced. This should prevent cells from breaking open as easily if things get a little toasty. The testing procedure for manufactured cells has also been revised. The design of the complete battery pack has been altered to operate in a narrower voltage range to reduce heat. Additionally, a new charging system was developed to prevent over-charging damage. Lastly, Boeing developed a battery enclosure to protect the aircraft in the event of a failure.In order to convince the FAA that the new battery was safe, Boeing did extensive testing where the batteries were intentionally driven to failure. The original packs failed in about an hour under the stressful test conditions. When they failed, they failed big. All the cells vented, the casing was breached, it caught fire, and things reached nearly 300 degrees C. The new battery never came anywhere close to those temperatures, and when it did eventually fail, only two cells vented. There was no fire, and things were brought under control easily.Boeing has put together teams to do on-site modifications of existing planes, and all new aircraft will have the updated battery. Even with custom installation kits, it will take five working days to upgrade and test each plane.While Boeing might have found a solution, there is no telling what this episode has done to the Dreamliner’s reputation.The root cause of the failure is still not completely understood, but the new, more hearty battery seems unaffected by the issue. The company claims airlines are still interested in buying the 787, but rival Airbus has backed off plans to use lithium-ion technology in its next generation planes.If you find yourself in a 787 in the future, rest assured a lot of work went into making it safe. Hopefully this is the end of Boeing’s Dreamliner headaches.