12V battery

[Crissa]

Has any EV owner ever brought a dead or confused system back to life with a portable 12v jumper unit long enough to get home? Does it makes sense to carry a small one with you? What are your thoughts? I know not every battery is exposed and user friendly like ID4 but if you could get to it easily on CT, would you carry a 12V backup plan?

Yes. Although most of these systems aren't designed for a continuous load. And the earlier EVs were kinda ridiculous to get to the accessory battery.

-Crissa

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[pagesix1536]

Wasn't Elon talking about trying to go to a 24 or 48 volt system, but couldn't because they couldn't convince 3rd party suppliers to change their stuff over? I don't understand why they can't run that stuff on a set of buck-down voltage converted circuits at 12v, and then power the Tesla proprietary stuff at the higher voltages.

 

[pagesix1536]

Has any EV owner ever brought a dead or confused system back to life with a portable 12v jumper unit long enough to get home? Does it makes sense to carry a small one with you? What are your thoughts? I know not every battery is exposed and user friendly like ID4 but if you could get to it easily on CT, would you carry a 12V backup plan?

Yes.. I've done this many times with my Leaf and another vehicle to "jump start" it when I had a completely dead 12v battery. You only need to supply 12v power to the EV to just boot up the computers and get them to switch on the contactors for the main drive battery. Once that all takes place, the drive battery then supplies power to the 12v inverter on the car which continues to supply 12v after you disconnect the jumper cables. You can drive your EV normally, until you turn it off again. Then it would need another "jump".

 

[Diehard]

Yes.. I've done this many times with my Leaf and another vehicle to "jump start" it when I had a completely dead 12v battery. You only need to supply 12v power to the EV to just boot up the computers and get them to switch on the contactors for the main drive battery. Once that all takes place, the drive battery then supplies power to the 12v inverter on the car which continues to supply 12v after you disconnect the jumper cables. You can drive your EV normally, until you turn it off again. Then it would need another "jump".

Thanks a bunch. This is very helpful. I assume you are OK when you stop at red light (car does not shut itself off and inverter still working)?

 

[Crissa]

Wasn't Elon talking about trying to go to a 24 or 48 volt system, but couldn't because they couldn't convince 3rd party suppliers to change their stuff over?

He was talking about using PoE, yes. https://en.wikipedia.org/wiki/Power_over_Ethernet

But the problem isn't that they can't make the parts, but that they have to invent an entire market. Which at this point would mean even more custom parts which would raise the cost.

And yes, dc-dc that drops the voltage is much more efficient. But you still prefer to know the amperage of the load as a steady amount, which isn't a concern with AC, but is a big deal for DC.

-Crissa

 

[android04]

Thanks a bunch. This is very helpful. I assume you are OK when you stop at red light (car does not shut itself off and inverter still working)?

Yes, stopping and even putting the car in park would be fine and the car would still be alive. In the case of Teslas, the only time the HV contactors disconnect (and the DC-DC converter would stop supplying 12v to the car and lead acid battery) is when the car goes to sleep. That happens about 15 minutes after you leave and lock it.

 

[Diehard]

Yes.. I've done this many times with my Leaf and another vehicle to "jump start" it when I had a completely dead 12v battery.

Did you ever get any warnings, or symptoms with some functions acting funny before everything was completely dead?

 

[rodmacpherson]

Has any EV owner ever brought a dead or confused system back to life with a portable 12v jumper unit long enough to get home? Does it makes sense to carry a small one with you? What are your thoughts? I know not every battery is exposed and user friendly like ID4 but if you could get to it easily on CT, would you carry a 12V backup plan?

My 2012 LEAF's 12v battery went flat after being left unplugged and unused for several weeks last year. opened the door with the manual key, popped the hood connected the jump start battery and turned the car on. drove to work and have never had an issue again.
As long as you can start the computer that operates the start up procedure that connects the HV battery system to the DC/DC converter you are good. You could probably do it with a pack of AAs in series to get 12V.
Once the car is on you can disconnect the jump battery and close the hood. The DC/DC converter will charge up the 12v while you drive.

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