[function_seven]

I remember my surprise when I learned EVs have regular car batteries in them.

The funny thing is, I can imagine a future where "jumper cables" isn't a hefty set of thick wires intended to supply the current needed for a starter. Instead, people will have a 20' long cable with cigarette lighter plugs on both ends. The HV relay can't require that much current to close, right?

[sandworm101]

Maybe, but the dead battery is still in the circuit. So a tiny wire won't provide enough current to raise the voltage enough across the entire circuit. (I assume that it requires something akin to a the solenoid of a IC car.) You don't need the cranking amps, but you will still need something thicker than a USB cable.

[function_seven]

Ah, good point. I guess it matters whether your battery is drained, or dead. Sometimes the battery just doesn't have the juice to turn the starter (you hear the clicking of the solenoid when trying to start, but no cranking). Other times it's so depleted that an external current supply will be sucked up by the thirsty battery.

[hanche]

It probably won’t take a large current, but I expect you need more than just enough to close a relay. Most likely, you’ll need enough to power some CPUs and data buses as well. That’s still tiny compared to the current required to run a starter motor, though.

[amluto]

There’s a different problem with your scheme. Tesla doors won’t unlock if the 12V system dies.

[8note]

I could see it being a push button switch instead, manually closing the relay.

But if the 12V is dead, the stuff running off of it will also be out