the Buick comes to a stop, its Maneuverability reduced to zero and unable to drive on. The car battery is completely dead and it won’t start.
This completely broke me out of immersion, and as a player I'd be wanting to argue with the GM that that makes no sense.
The problem is this. Once a car is started it doesn't need the battery any more. The power comes from the alternator. After ignition the battery's power is only used if the alternator has died. In that case the car will suck power from the battery until there's none left, and then die. However, in that scenario replacing the battery would get your car running, but you wouldn't make it far before the new battery was also drained.
I understand that later on it's semi-explained via the not-quite-magic of the entity sucking power, but the player doesn't know that until near the end of all this. This completely broke immersion for me. As I read on I kept thinking about how the entire reason we're stopped here makes no sense.
I'm not sure what a good solution to making the car stop in a way that can be easily repaired, but anyone who knows anything about how a car works electrically is likely to be tripped up by this. Even knowing the cause I'm still wondering if that would actually stop the car, because you can bump-start many cars with dead batteries so, even if the being sucked ALL the power for a moment and caused the car to die, it'd probably start right back up because it was in gear AND in motion at the time.
Once you get past that there's also the question of what happens to all the other battery powered things the players might be carrying, including (i assume) drones. The way its described it's like some sort of proximity field, so it wouldn't be able to target only car batteries, and not phone batteries, or calculator batteries, or whatever.