And when you're sued and/or criminally charged, your lawyers can bring that up that your vehicle passed inspection (unless it was still being built in your garage), before the lithium battery fire that involved the "ZombieVerter that you built from plans you found on the Internet".

Even if it can eventually be proven (to the judge/jury) that the ZombieVerter performed perfectly, and that you were not at all negligent or reckless, that's going to be drawing suspicion and blame.

While defense costs bankrupt you.