What happens in the edge case of losing HV during heavy braking on the freeway? Does the brake booster still function independently of the HV system, or is the driver going to have to push the pedal a lot harder?
You obviously wouldn't be able to speed up again, which depending on the situation, would be where the danger lies.
Tesla buys plenty of products from them, including things like electric steering assist.
Bosch wants to stay relevant for longer than ICE cars after all, and a lot of these components were developed for ICE cars anyway.
But e.g. why have different electric window motors, wiper motors, turn signal solenoids etc etc?
Availability of accessories seems like it would be inconvenient for any early adopters, e.g. you can readily get USB chargers, portable generators, coolers, tire inflators, battery boosters, etc. that run off 12V... if you get a 48V vehicle today, you'd either need a 110V->12V adapter to run accessories, or you'd be limited to 48V RV accessories.
Virtually all electronics need a step down (buck) converters as they run at lower voltages 5, 3.3, 1.8. 12V > 3.3- 1V would a single step. 48V ones would likely require an intermediate step. The only exception would be running some power systems where it'd require less current.
The main savings is current though, because the wiring harness is one of the most expensive parts of a car.
There are a few different topologies for a 48v harness, but somewhere in the line there's a 12V DC/DC converter in there somewhere.
The wiring for 48V can be a lot thinner than it is for 12V. As there is a square law involved for resistive heating it turns out that wiring for 48V can use 1/16th of the weight of copper as that for 12V.
A switchmode converter can be designed for 48V just as easily as 12V.
Hobbyist computing could benefit from a move to 48V as well, if only to keep the problematic 12VHPWR from killing expensive video cards.
I say hobbyist because AIUI 48v is making inroads in server hardware but that's not my area.
You generally can't reuse non-automotive power supplies in automotive because the requirements are very different.
I have to wonder if this ever happened with the 6v to 12v transition somewhere in the 50's-60's
Vacuum break boosters only make sense for ICE vehicles where you already have an existing air pump (the actual engine) providing free “vacuum”, they don’t make sense in EVs where you need to an extra dedicated motor to produce vacuum, to power a vacuum booster system, to boost the breaks. Much better off just using the extra electric motor to directly boost breaks, without the whole vacuum system as a middle man.
Early EVs use vacuum break boosters, but only because they were the only economical solution, given there was little demand for electric break booster systems. After all a vacuum system is cheaper, if you have a free “vacuum source”. But for last decade or so there’s been enough EVs manufactured that electric break booster systems are now more economical for EVs.
To answer GP question, the an electric break booster system is almost certainly powered off the low voltage (12V) accessory system, not the high voltage system. So a high voltage disconnect won’t prevent the break booster from working, assuming the LV battery is working correctly.
Is an EV like an ICE in that the 12V bus has power while the car is running even if the 12V battery is dead? In an ICE the alternator puts 13.5 volts onto the 12V bus so a dead battery will prevent a car from starting but it will stay running on a dead battery if boosted to start. I imagine an EV does something similar but I don't know.
The 12V battery dying is only an issue if the car is parked and the high voltage battery is disconnected. Then there may not be enough power to 'wake' the car up again.
Mine failed after ~5 years. Replacement was inexpensive ($128) and Tesla service drove to my house to install it.
Like another poster in this thread, my original model 3 battery went ~5 years (typical 12v failure age in a car), and I bought it for $89(!!) at Tesla. Autozone wanted $125 for the same group battery. I did a DIY replacement. For some reason, that one failed after a year and a half. Just bad luck I guess.
Some EV makers, including Tesla, have switched to Li-ion (often LFP) low-voltage batteries. These tend to be better suited to EV duty cycles than lead-acid, and improve reliability and longevity, as well as saving space and weight.
To lecture us on EV brake systems while repeatedly misspelling the word is making me twitch far too early this otherwise fine Wednesday morning.
As to whether the booster is run off of the 400V or 12V bus I don't actually know. My guess would be the latter, honestly, since the parts would be more generic. But in any case it probably doesn't matter if the main battery fails as the 12V battery is tiny and would probably not provide enough power to run the hydraulics without the DC/DC converter.
LiFePO4 is capable of providing massive amounts of current for its size (way higher than a conventional acid one). 100A is not that high amount of current to run even with 4s4p setup. A 10kg battery would be beyond sufficient (should be able to fully power the brake system for 1h use).
Note: jump on the brakes is expected to consume around 1200W
I don't have the exact weight, but Tesla's LFP low-voltage batteries weigh far less than that. Around 2kg at a guess.
Rating is 12.8V nominal, 12Ah, 153.6Wh. Not all that much bigger than a laptop battery!
But I really don't think hydraulics like power steering/braking are on that list. The fallback for hydraulic failure is manual pressure, just like it is on any car. It's a naturally redundant system.
Either way, the battery is indeed 'tiny'
Again, Tesla brakes are very conventional hydraulic devices and they work (and fail) like brakes in any other car you're going to drive.