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Car companies, starting with Volvo last summer, have laid out plans to electrify entire lineups of vehicles. But the fine print makes it clear that the coming decade and beyond will focus not just on massive battery packs powering electric motors, but also on adding a little extra juice to the venerable internal combustion engine.
Increasingly, that juice will arrive in the form of new electrical systems built to a 48-volt standard, instead of the 12-volt systems that have dominated since the 1950s. Simpler than Prius-type drivetrains and less expensive than Tesla-scale battery power, the new electrical architecture both satisfies the demands of cars made more power hungry by their gadget load and enables the use of lower-cost hybrid drive systems.
https://www.nytimes.com/2018/02/08/business/electric-cars-48-volts.html
(Score: 2) by sjames on Monday February 26 2018, @03:52AM (10 children)
Cost. The 12v rated contacts in all the switches won't stand up to 48v at all. All of the off the shelf motors, switches, etc are 12v. Those instrument clusters all run on 12V. Basically, adding a voltage converter will be a LOT cheaper than redesigning all of that and totally replacing all of those off the shelf parts.
(Score: 4, Insightful) by Grishnakh on Monday February 26 2018, @04:01AM (9 children)
Mostly wrong.
1. Instrument clusters: no one reuses instrument clusters. Every car has a different one, and every car gets a completely different one when it's redesigned for a new generation. You have to redesign your instrument cluster every 3-6 years anyway, so designing it for 48V is no extra cost.
2. Switches: lots of stuff is going away from high-current switches, and moving to extremely low-current switches with MOSFET power switching circuits. This lets you use the vehicle network to get commands from switches, and then remotely actuate stuff elsewhere in the car (like in a different door, in the case of window switches), so wiring is simpler and you don't need to route high-power wires all over the place.
3. Motors do get changed from time to time. 48V motors are smaller and cheaper than 12V ones because you need much less copper winding to get the same torque.
(Score: 2) by sjames on Monday February 26 2018, @04:30AM (8 children)
The cluster itself may change from year to year, but the parts that make up the cluster don't.
Perhaps going away, but far from gone.
in the same volume with the same available data on lifetime, 48v motors would be cheaper. But 12v motors for automotive applications are in volume production and have been for a long time.
(Score: 2) by Grishnakh on Monday February 26 2018, @06:26AM (7 children)
The cluster itself may change from year to year, but the parts that make up the cluster don't.
They absolutely do: every new cluster means you need an all-new PCB designed. If you're going to redesign the PCB, you might as well redesign the power supply on it. Why on earth would you stick the same 12V power supply on there, and then design in a 48V-to-12V DC-DC converter somewhere, when you can just slightly modify the power supply on the cluster PCB to handle 48V?
(Score: 2) by sjames on Monday February 26 2018, @06:43AM (4 children)
Because you already need the 12V converter, so it comes "for free"
(Score: 2) by Grishnakh on Monday February 26 2018, @03:59PM (3 children)
What do you need the 12V converter for? No, it's really not "free": adding more 12V loads means your converter needs to be upsized, and you need heavier-gauge copper wiring to these loads where you were too lazy or stupid to just modify the design for 48V operation when you were redesigning it in the first place. This doesn't make any sense at all.
(Score: 2) by sjames on Monday February 26 2018, @07:10PM (2 children)
People expect the aux power socket (the "lighter") to provide 12V at a decent amperage. After-market equipment is expected to just work.
EVENTUALLY, the 12V will go away entirely. I think you way under-estimate how much carry-over there is from year to year in design. Automotive engineering is quite conservative as a whole.
There's a reason that part catalogs generally include a list of model and year ranges that the same part fits. Warranty repairs and recalls are expensive and damaging to reputation.
(Score: 2) by Grishnakh on Monday February 26 2018, @07:33PM (1 child)
Yes, it is conservative and a lot of parts are carried over, but that does not include instrument clusters (they're always updated with new generations, and sometimes in the middle of generations too), nor does it extend to circuit designs. As I said before, it would be completely idiotic to design an all-new instrument cluster PCB and not bother to design in a new power supply if you have a 48V bus available. It's not like designing for a 48V supply instead of 12V is something completely new and different. And you're not going to use the same DC-to-DC converter for a lighter socket as for something critical like your instrument cluster; that too would be idiotic, because someone could plug something into the lighter socket causing the DC-to-DC converter to fail, and now your dashboard is dead.
(Score: 2) by sjames on Monday February 26 2018, @09:10PM
As opposed to now where someone could plug something into the lighter socket and the whole electrical system is dead?
Or more likely in both cases, a fuse blows and life goes on.
(Score: 2) by hamsterdan on Monday February 26 2018, @11:31PM (1 child)
Don't underestimate bean counters. My friend's leaf has a standard 12v lead acid battery, even if the car is 100% electric. when his battery died, the car wouldn't start. because the single 12v battery was dead. An F-150 gave him a boost, a V8 gas-guzzling jump-started an electric car, so yes, everything is possible.
One of the advantages of switching to 48v is wire size, even on gas-powered vehicules, we're talking about lots of pounds that could be shaved from the vehicule's weight, but if they leave legacy 12v in there for *everything* on the market, fine by me. For those of you old enough to remember the cigar lighters in cars, it was a legacy from when it was really used to light cigars.
(Score: 2) by Grishnakh on Tuesday February 27 2018, @03:02AM
The Leaf most likely has a 12V battery because off-the-shelf parts from Nissan's parts bin are all 12V, and a single not-top-selling model just isn't enough to get a bunch of 48V accessories made (which wouldn't help the Leaf that much at this point anyway, because its main battery is 380V, and the auto industry has been talking about a new voltage standard for decades but never actually agreed to one). If a large carmaker switches ALL its models to a new voltage standard, the old 12V stuff will be disappearing pretty quickly, if not within one car generation, definitely two.
Here's [mynissanleaf.com] an interesting post about those Leaf batteries BTW.