Originally Posted by Guy..
I don't see the issue in intentionally breaking the circuits again when he puts it back. Afterward he can then just hop back in his train and head to whatever time period he wanted. Bear in mind he built that train in the 1880's with Clara.
There's also the fact that the car would need to be in the exact condition it was in when Doc put it in the mine in the first place. That means intentionally shorting out the time circuits with lightning.
Why is the given explanation so hard to swallow? If you listen to the letter, Doc refers to a "gigawatt overload" that was what activated the flux capacitor. If you think about it, the raw lightning probably sent way more than 1.21 gigawatts into the car, and might even have hit double that. That, I think, would be enough to make the flux capacitor double the DeLorean. And since it was sent 70 years forward and back through time, there's a nice symmetry. And Doc was probably glad to find the second DeLorean, the train can't be a great way to time travel. It's not exactly quiet.