It said the battery had expired 15 months prior to the Malaysia airliner's disappearance. The report also said there was no evidence the plane's crew acted abnormally ahead of the flight.
The cockpit voice recorder indicates the co-pilot appears to have deliberately crashed the plane carrying 150 people into the French Alps. A German tabloid reports he was being treated for depression.
His flying club says Lubitz "wanted to see his dream of flying fulfilled." Investigators say he appears to have deliberately crashed Flight 4U 9525 into the French Alps, killing 150 people.
Islamist insurgents have reportedly killed about 40 people, as the polling for a new president continued into Sunday. Voting was extended after technical problems kept some from casting their ballots.
But a prosecutor says "documents don't show any hints of [Andreas Lubitz] being suicidal or being aggressive toward other people." The plane crash last week killed 150 people.
Boko Haram extremists are being blamed for more than 40 deaths, including one lawmaker, as balloting continues in a closely fought presidential election.
With Tuesday's deadline for an international agreement on Iran's nuclear program approaching, foreign ministers from Iran and six world powers are trying to hash out a deal.
Francis noted that schoolchildren were aboard the aircraft thought to have been deliberately crashed by its co-pilot. The pontiff also paid tribute to "martyrs" killed for their faith.