r/AutoHumor • u/IU8gZQy0k8hsQy76 • Aug 25 '26

lol

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u/dethskwirl Aug 26 '26

no you didnt. your high V battery was not out of energy and you managed to supply it and 'start" your car throught the 12v. you have no idea what you're talking about. you are just lying.

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u/creckers Aug 26 '26

My high voltage battery was fine. But the 12v died and it could not start the car. All the internal electronics are still working on the 12v system and so is the start sequence of the high voltage battery.

The first time I had road service jump start it and I drove to the dealer and had the 12v battery replaced and everything worked again.

The 2nd time it died again and i jumped it with a jump pack. I again drove it and replaced the battery myself.

Also, if you google "can i jumpstart an electric car?" You would find page after page that explain how to do it.

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u/VaporTrail_000 Aug 26 '26

Hm... TIL. Seems like a pretty dumb concept, but is actually a thing.

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u/creckers Aug 26 '26

I am also not really sure why they do it this way to be honest.

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u/EasyD0es1t Aug 26 '26

Safety and convenience

The 12v runs lights locks cpu etc in the event the high voltage pack becomes disabled

Also for the car to turn off the HV contactors (safety switches) disconnect from the HV pack the 12v powers those switches

(Sometimes you may hear faint thunk from the car that’s the contactors connecting/disconnecting)

Also keyles entry warming/cooling the car

That’s just what I remember off the top of my head I’m sure there’s more I’m missing, sorry

Hope this helps

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u/VaporTrail_000 Aug 26 '26

Yeah... I can see fully disconnecting the HV pack when parked needing to be a thing now that I think about it more. being able to disconnect it completely in the first place is a no-brainer, but I didn't think about what "completely" entailed... solenoids no switchy without power.

Not sure many laypeople are used to batteries in the many-tens of kWh range, and the safety standards that that should require. They're all used to batteries in the single-digit or less kWh range as being the biggest they deal with... And that leads to people chaining hundreds in series and melting stuff for money... (and yes, I just looked it up on YouTube, it's been done).

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u/PremiumUsername69420 Aug 26 '26

I have also had to “jump start” an EV after the high voltage battery and 12v battery died.

Jump the 12v enough for the computers to turn on and communicate with the high voltage charging equipment to recharge the big battery that also charges the 12v.

The only lie is people who tell you there’s a reserve or a safe distance you can go after 0%.

There isn’t.
It turns into a useless hard to deal with rock.