EV Crew: I have a question...

Mr. Kitty Litter

Feelin’ generous?
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Jun 3, 2004
31,576
The Metaverse
So... I've owned 2 EVs, and at some point each of them required the 12v battery to be replaced and/or jumped.

It makes absolutely no sense that a dead or faulty 12v battery will render a fully charged EV practically useless, as the car will not "start". As expensive as some of these cars are, wouldn't the logical thing be for the system to be able to pull power from the bigger, main battery that powers the drivetrain? At the price point some of these cars are at, I am shocked that this isn't included.

Why havn't we seen this? It was so furious one morning when my 12v died, and I couldn't move the car even though it was fully charged from being plugged in over night.
 

herpes

OT Supporter
Jun 4, 2005
142,136
dfw
how much do you fuckin suck that you've somehow allowed a battery to die on any vehicle? maybe next time ask your husband to take it to autozone and have them replace it for you.
 

whatever

OT Supporter
Feb 18, 2004
212,076
because 400 or 800v lighting circuits are dangerous :rofl:

putting a 400v button onto the steering wheel. etc etc.


now why isn't the 400/800-12vdc transformer able to handle it? because you'd need to size it for max draw vs letting the small 12v battery be a buffer to large transient draws. you also have the weight issue. I bet its lighter.
 

Tenny

OT Supporter
Oct 4, 2005
16,338
Houston
All of the interior lights and general stuff run off / expect 12v. I think there's even something to do with OBDII requirements or something.


Of course there's ways of getting 12v off the high voltage sides, but you are either going to have bad efficiency or you are going to ruin the balance on the HV batteries.
 

HoodRich

Professional Street Nigga
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Feb 2, 2004
82,973
The City
12v lead/acid batteries are much less expensive than 12v lion batteries. Also, this isnt a concern for most sane people
 

jelloslug

OT Supporter
Jul 1, 2003
60,229
Greenville, SC
It's done this way to keep the high voltage battery as isolated as possible when the car is not actually in motion. At some point in time, the 12V system will be completely eliminated but that will also require a complete redesign of all accessory components.
 

whatever

OT Supporter
Feb 18, 2004
212,076
It's done this way to keep the high voltage battery as isolated as possible when the car is not actually in motion. At some point in time, the 12V system will be completely eliminated but that will also require a complete redesign of all accessory components.

i'd expect 48v POE/ethernet stuff. I know elon is pushing it.
 

Topgun

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May 23, 2003
28,238
MN
It's not safe or smart to keep a 400v+ system connected just to run a 12v computer 24x7.
 

whatever

OT Supporter
Feb 18, 2004
212,076
to answer your direct question:

the contactors are controlled by a 12v circuit. the control boards are 12v. without the 12v bus the battery won't even connect to the inverter.
 
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Mr. Kitty Litter

Mr. Kitty Litter

Feelin’ generous?
OT Supporter
Jun 3, 2004
31,576
The Metaverse
how much do you fuckin suck that you've somehow allowed a battery to die on any vehicle? maybe next time ask your husband to take it to autozone and have them replace it for you.
They had a few years on them, when I bought the cars :o
i'd expect 48v POE/ethernet stuff. I know elon is pushing it.
That would be an interesting change...
 

whatever

OT Supporter
Feb 18, 2004
212,076
They had a few years on them, when I bought the cars :o

That would be a interesting change...

Yea. 1/4 the wire size for same wattage needs. one loop around the car with stops at all the devices. done and redundant. only headlights would need their own power direct stuff without going POE++++++
 

jelloslug

OT Supporter
Jul 1, 2003
60,229
Greenville, SC
i'd expect 48v POE/ethernet stuff. I know elon is pushing it.
I think Tesla will be the first to do it. All the other manufacturers have been talking about 48V systems for decades but none of them have even made the first effort to try. I would guess that a 48V system would cut at least 100lbs out of the car.
 

herpes

OT Supporter
Jun 4, 2005
142,136
dfw
They had a few years on them, when I bought the cars :o

That would be an interesting change...
lol i didnt drive my s2000 in a year and the tiny fuckin battery in it still wasnt dead

i didnt drive wife's mini cooper in like 6 months and the same

how about you stop leaving your headlights on ya fuckin woman
 
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whatever

OT Supporter
Feb 18, 2004
212,076
I think Tesla will be the first to do it. All the other manufacturers have been talking about 48V systems for decades but none of them have even made the first effort to try. I would guess that a 48V system would cut at least 100lbs out of the car.

Yea I know GM back in the day was really trying for a 24v system due to big SUV demands.

but a POE ethernet system makes a lot more sense. control and power wires together on super light wires with a long history of applications.
 
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herpes

OT Supporter
Jun 4, 2005
142,136
dfw
Yea I know GM back in the day was really trying for a 24v system due to big SUV demands.

but a POE ethernet system makes a lot more sense. control and power wires together on super light wires with a long history of applications.
this doo gonna put POE cams on his car
 
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Mr. Kitty Litter

Mr. Kitty Litter

Feelin’ generous?
OT Supporter
Jun 3, 2004
31,576
The Metaverse
Yea I know GM back in the day was really trying for a 24v system due to big SUV demands.

but a POE ethernet system makes a lot more sense. control and power wires together on super light wires with a long history of applications.
I remember hearing about that, a few years ago.

It's like...GM has great ideas for innovation, yet they are rarely the first to come out with anything new.
 

whatever

OT Supporter
Feb 18, 2004
212,076
I remember hearing about that, a few years ago.

It's like...GM has great ideas for innovation, yet they are rarely the first to come out with anything new.

yea they do not move quickly at all. sandy monroe talked about his time at ford. lets do X Y Z and save millions. nope not interested.
 

jeri534

OT Supporter
Jul 17, 2002
19,382
I think Tesla will be the first to do it. All the other manufacturers have been talking about 48V systems for decades but none of them have even made the first effort to try. I would guess that a 48V system would cut at least 100lbs out of the car.
There is actually some implementation of 48v in vehicles in the market right now, but not in the scale you are talking about.
 

jelloslug

OT Supporter
Jul 1, 2003
60,229
Greenville, SC
What do you mean at a manufacturer level? VW group uses it in a bunch of vehicles already
That's mild hybrid stuff, not 12V replacement. GM was doing that 10 years ago. When I was designing electric motors for a living, I designed the motor for one of GM test beds back in '04.
 

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