271–280 of 504 posts
Older Tesla cars have a 12V battery for accessories, until the main high-voltage battery is turned on. So does this mean having a 48V accessory battery? Or what?
It's probably a modified version of the '16V' lithium battery in all other Teslas, just with 3x the pack voltage.
Many comments here seem to be confusing the accessories circuit voltage with the electrical vehicle motor and drive system. The vehicle motors have a combined power output of 450KW which requires a high voltage 800V system or the wiring would be so heavy it would not be feasible. This spec appears to be the accessories circuit with Tesla pushing for a new 48V standard. That’s super smart because it immediately means…
It simply has never been worth it before to retool things in practice.
It's also electrically a lot more noisy. The limit of what is considered low volt is like 60v or something.
Earlier quoted context omitted.
>and the jumper pins It can be started through the converter? That takes something like a hundred amps. It must be pretty beefy.
No. For safety, hybrids and electric vehicles physically disconnect the high-voltage battery from everything when it's off with massive relays. So you can end up in the somewhat stupid situation where your high-voltage battery is fully charged, but you can't do anything because the tiny 12v motorcycle battery is flat. Starting simply requires enough 12v current to close a relay, the amps going though the "jumper pins…
Earlier quoted context omitted.
> This is an older article but explains it well https://www.greencarcongress.com/2017/06/20170602-audi.html From the article: > The 12-volt system is connected to the main electrical system via a DC/DC converter > Audi also offers the new MHEV technology with the conventional 12-volt electrical system > 48-volt vehicle electrical system. In a different layout—without MHEV—the 48-volt constant voltage system already e…
Realistically, using 12 volt and 48 volt for accessory systems are pretty similar. 48 volts just reduces your current, and you have to design everything for ~56 volts instead of ~14. But it's not really a different exercise.
"Just" is doing an awful lot of work in that sentence.
Yes, moving from 12v to 48v reduces the current. That means you can have much smaller gauge wires, it means you lose a lot less power ( powerloss = (II)R ), it means you use a lot less copper and it means you save a lot of weight on wiring and connectors.
That is literally the point.
Earlier quoted context omitted.
>and the jumper pins It can be started through the converter? That takes something like a hundred amps. It must be pretty beefy.
No. For safety, hybrids and electric vehicles physically disconnect the high-voltage battery from everything when it's off with massive relays. So you can end up in the somewhat stupid situation where your high-voltage battery is fully charged, but you can't do anything because the tiny 12v motorcycle battery is flat. Starting simply requires enough 12v current to close a relay, the amps going though the "jumper pins…
I liked the interview with auto engineer Sandy Munro discussing the change https://youtu.be/ADwGGEj8sqQ?si=qp6akvy1yyWPTYNe - moving the voltage up means you can drop current - increase the data rate by using ethernet and PoE - using ethernet and PoE means you don’t have to run one off wires to each device, they can share a bus which results in half the copper being used in a lower voltage car - moving the voltage up…
> using ethernet and PoE means you don’t have to run one off wires to each device, they can share a bus which results in half the copper being used in a lower voltage car You mean like CAN bus is being used since 1990s? I think that Mr Munro little bit fell asleep and missed whole CAN bus and FlexRay evolution in cars.
Earlier quoted context omitted.
Smaller transformers with whole numbers, right? But why 4 and not 3 or 6?
We seem to stick with 7-smooth numbers, and really extra prefer highly composite numbers ( https://en.m.wikipedia.org/wiki/Highly_composite_number ) for things we chose before the age of calculators. 3 and 6 were the standard voltages for consumer stuff back in the days of people needing to buy multiple packs of AA cells every year
Many comments here seem to be confusing the accessories circuit voltage with the electrical vehicle motor and drive system. The vehicle motors have a combined power output of 450KW which requires a high voltage 800V system or the wiring would be so heavy it would not be feasible. This spec appears to be the accessories circuit with Tesla pushing for a new 48V standard. That’s super smart because it immediately means…
48V has been considered for automotive for decades. The problem was not know how. It simply has never been worth it before to retool things in practice. It's also electrically a lot more noisy. The limit of what is considered low volt is like 60v or something.
Many comments here seem to be confusing the accessories circuit voltage with the electrical vehicle motor and drive system. The vehicle motors have a combined power output of 450KW which requires a high voltage 800V system or the wiring would be so heavy it would not be feasible. This spec appears to be the accessories circuit with Tesla pushing for a new 48V standard. That’s super smart because it immediately means…
Earlier quoted context omitted.
48V has been considered for automotive for decades. The problem was not know how. It simply has never been worth it before to retool things in practice. It's also electrically a lot more noisy. The limit of what is considered low volt is like 60v or something.
Why is it inherently noisier?