Originally Posted by Gumbyfan
When the time machine was struck by lightning in 1955, the direct overload in the flux capacitor created TWO cars. One landed in the end of the first movie with Marty. The other was flung 70 years into the future.
Doc's referring to the 1955 lightning at the Lyon Estates sign, that sent Doc 70 years into the Past to 1885. The other one appeared 70 years into the Future, in 2025. He didn't have to re-add Mr. Fusion, just repair the Time Circuit Control microchip and, possibly, the flying circuits.
Now, lucky it didn't land on somebody's home