This has been a real head-scratcher for me. BMW and other automakers could have vastly improved their cars by switching to 48V a decade ago, but they still keep just plodding along with 12V.
I have no explanation for this.
I have no explanation for this.
Tesla didn't have any existing, so their clean-slate math was clearly in favor of 100% new technology.
(Well, they did have 12v existing in their other cars, but they were clean-slate in the truck.)
I designed some stuff along these lines 15 years ago. At that time, 12 volt stuff was not just available, it was available with great economies of scale and a huge range of options, off the shelf. You need an automotive-qualified relay? A light? A solenoid? A DC-DC converter module? A fan? You'd have 100 choices at 12v, 30 choices at 24v and 3 choices at 48v.
The microcontroller still runs at 5/3.3/1.8 V.
Major car components like doors or front axles are assembled in parallel to miscellaneous parts on the main body, and all .join() at the final assembly. This had been the case for past 30-50 years, possibly more, in case this needs to be said.
> Major car components like doors or front axles are assembled in parallel
And doors (and tailgates) are the biggest body component that is _sometimes_ assembled independently. Then workers manually route cables through the body.
Pre-routing cables inside panels that can then just be welded together can save a lot of labor.
Sometimes? What and when on Earth is this about? Pre-WWII?
They wash and paint and dry the whole body at once _for paint consistency_, then take off doors and trunk lids and bumpers and send them into separate assembly lines. Those major parts flow parallel "threads" in sync and converge near the end, where connectors are plugged in and those major parts are bolted back in and plastic trims are pushed in to tuck everything under. Cars were basically always done that way for a long time everywhere. I think even lots of hand made supercars are like that, only except tact times are magnitudes longer.
> Then workers manually route cables through the body.
> Pre-routing cables inside panels that can then just be welded together can save a lot of labor.
What do these even mean? Are you hallucinating workers crimping cables in-situ? They just clip on harnesses and plug in couplers in "the line". Never seen under a door trim?
It sounds like you're either extremely ill-informed, or worse yet, potentially, intentionally misinformed about car manufacturing that what you see is advanced manufacturing. I think you should... look more closely into what "legacy auto" have been doing forever.
Workers still need to pull the wiring bundles through the car body and clip them, after the body is welded together. The connectors are impractically bulky to put several of them along the cable routes.
Pre-assembled panels can have cable runs attached to them during the individual panel assembly.
Tooling all their shit to 48V is a massive undertaking with pretty much zero advantages.
You really need some special component that is much better at 48 for it to be worth it, otherwise a delayed platform switch is better; one some competitors have moved and the suppliers exist.
They _all_ benefit from 48V.
It's very, very hard to get insulation that's not good for at least 100V and I suspect that just about any generic wire is good for more like 300V.
The only exception that comes to mind is wire that's specifically for "household low voltage" like 24V AC for thermostat, doorbell, sprinklers, landscape lighting. Also normal ethernet. But these are almost all what you'd call signalling wiring rather than power wiring.
Your average hook-up wire that you could buy at the auto parts store to make some repairs is almost certainly rated for 300V already. Mostly because of chafe resistance. Wikipedia says that the dielectric breakdown strength of PVC is 40 millions volts per meter https://en.wikipedia.org/wiki/Polyvinyl_chloride.
Divide both sides by 1 million and you get 40 volts per micron. OK so you need 1/3 of a micron to insulate enough for 12V and you need 1.25 microns for 48V. Now let's have a reasonable safety factor of say 10 or so and we're looking at 3 microns vs 12.5 microns. The only wire I can think of that might have insulation that thin is enamel coated magnet wire for the inside of motor windings. But even that is probably thicker.
Any kind of plastic insulation is going to be significantly thicker than this just to be able to be coated onto the bare copper wire and stick.
You're not wrong that the insulation needs to be thicker as the voltage goes higher. But you're unaware of just how ridiculously over-insulated everything already is due to other constraints of manufacture.
The integrated starter generator(ISG) is usually a pancake shaped motor that replaces clutch/torque converter in ICE car, nothing like the regular starter motor.
MHV was not even real hybrid, and is no longer relevant, so was 48V, at least for a while.