Employees were replacing low batteries on a wind turbine. They replaced two battery racks, replaced the covers, and attempted to start the tower. The tower then faulted on a faulty pitch master, so they replaced the pitch master. They then started preparing to program the pitch master when the entire battery rack exploded, creating a large bang and flash and throwing the cover across the hub, striking the injured employee in the back. The employee suffered three fractured vertebrae in their lower back.