[pgeorgi]

https://de.wikipedia.org/wiki/Bordnetz#48-Volt-Bordnetz_im_A... explains (a bit) why German car makers are using 48V since ~2016 (in addition to the still existing 12V system, which seems to be the difference with Tesla, which went 48V-only).

DeepL translation:

The 12 V electrical system can barely cover the power consumption that modern vehicles need for their comfort systems. The "static" consumers completely overload the alternator, which provides up to 3 kW of power, especially at low temperatures.[12] The battery power is not sufficient for additional dynamic consumers, such as powerful electrically driven compressors.[13]

For this reason, a proposal was made at the end of the 1990s to install a 14 V/42 V electrical system in motor vehicles.[14] From 2001, Japanese manufacturers and General Motors launched hybrid vehicles with this electrical system on the market.[15] Although Daimler-Chrysler was one of the co-initiators of this concept, it was not used in Germany. One reason for this was that it did not appear possible to demonstrate a corresponding utility value to customers for the necessary additional price[14].

Instead, since 2010, German car manufacturers have favoured the solution of providing a second 48 V electrical system to supplement the 12 V system.[9] Since 2016, the first series applications of 48 V electrical system components have been the operation of the electric compressor and the electromechanical roll stabilization in the Audi SQ7 4.0 TDI and Bentley Bentayga. Both are based on the same platform.

Translated with DeepL.com (free version)

[intrepidhero]

A split 48/12 system makes a lot more sense. Run the heater/heat pump, power steering, coolant pump, etc on 48V and keep entertainment and controls on 12V.

[bryanlarsen]

Computer chips use ~1.5V or so these days. Why go 48V->12V->1.5V when you can go 48V->1.5V directly? If it's more efficient to use an intermediate voltage, you can choose the most efficient intermediate voltage internally rather than using 12V.

[taylodl]

Because we already have the 12V infrastructure and part supplies in place. You're disrupting things for no benefit. We've been running split 24V/12V systems for decades now in automotive applications. It's not that big a deal to change that to 48V/12V systems as many European car manufacturers have done.

[bryanlarsen]

No benefit? I've seen estimates of $1000 in reduced cost due to reduced copper wiring, and more importantly the labor required to string that wiring.

Modern phones charge on 48V these days, so 48V parts are extremely common & cheap.

[Kirby64]

What modern phone charges at 48V? I'm not aware of any that charge at even 20V, outside of a couple of gimmick devices. No Samsung or Apple phone charges at anywhere close to that, that's for sure.

[bryanlarsen]

I believe Qualcomm's QuickCharge 5 can use the full 48V of USB-PD. Given it allows 100W, I certainly hope so.

Regardless, QuickCharge 3 is 20V and it's been in a lot of phones since it was introduced in 2016.

[smileysteve]

What modern phone charges at 12v?

Most phones charge at 5v. Modern USB-C chargers can charge between 5v and 20v based on configuration.

Buck converts and regulators are cheap and small these days.

[pgeorgi]

I'd fully expect other car makers to move to an exclusive 48V setup at some point. They just do it gradually: For the new model a part is replaced by its next-gen successor that is incompatible anyway? Put it on the 48V bus. Repeat until the 12V system is done away with - or force the issue when there are only a few components left, or downstep the 48V to 12V right in front of them, once that's cheaper than keeping the remaining 12V system.

[bryanlarsen]

It'd be cheaper to delete the 12V bus entirely and add 48V -> 12V converters in front of legacy components, even if they needed several dozen of those converters.

[jabl]

> I've seen estimates of $1000 in reduced cost due to reduced copper wiring

What about aluminum wiring? Lighter, cheaper, though bulkier than equivalent copper. Aluminum wiring got a bad rep back in the day, but it seems with current electrical aluminum standards it supposedly works pretty well.

[myself248]

Aluminum is hell to terminate. It basically requires ultrasonic welding; every trade-show has folks hawking various crimp terminals that're meant to break through the surface oxides during the crimp cycle, but not a single automaker has been swayed enough to use it on normal wiring.

The reliability concerns really add up with flexing fatigue, too. It's one thing to put aluminum wiring in a house where its only flex is due to thermal expansion, and it has a hard enough time coping with that it's still a special category in home insurance, to say nothing of a vehicle that's going to spend the next ten-plus years bouncing over the road.

Furthermore, you basically can't modify aluminum wiring. In-line splices and solders are virtually impossible. While that's irrelevant for manufacturing, it hits the aftermarket pretty hard, including dealer mods, and of course, dealer repairs. That can be worked around but it would require communication between branches who don't normally talk, and it just adds friction to any possible aluminum migration.

I've seen aluminum in a single very-heavy-gauge battery cable for a car that put the battery in the back, with ultrasonic-welded terminals on both ends, and that's it. Everything else in that car was copper.

[atoav]

In sotuations where it is about space you wouldn't choose aluminum. Also afaik most automotive wiring that is certified is copper. Going from copper to aluminum means you will have to put bigger crossections in. This is more weight and more space.

[taylodl]

What you may have saved on wiring is going to be offset by the increased cost of the battery (I'm seeing 2x-3x cost) and the fact you now need a much beefier alternator which is going to have its own cost.

You'd think if it were a slam dunk then the bean counters would have insisted on a transition to 48V years ago.

[jandrese]

Total current consumption should be about the same (or even less, thanks to lower losses at 48v), so I'm not sure why would you would need a "much beefier" alternator. It will need different windings, but overall it should be about the same size and cost.

[bluGill]

There is a lot of off the shelf 12V equipment you can buy. Plus even more that is sitting in garages ready to be installed in the next vehicle. Cars are manufactured in enough quantity that it would only cost $0.01 per vehicle to design it (plus parts costs which are probably the same), but that is still a few million to the bottom line if they use the same 12 volt radio. Add to that that ICE cars everywhere have 12 volt starters, and you can buy 12 volt jump start kits: when (not if!) a battery fails to start the ICE you better be able to jump start it from a 12 volt battery - this is a safety issue.

Tesla doesn't have ICEs, so the safety concerns are lost on them. Thus all 48 volt makes some sense. They still need something for all the accessories people have.