Why haven't we moved to higher DC voltages?

[j-c-c]

Not a direct "engine" issue, but certainly engine related, and the automotive world has been stuck on 12 v for over 50 years after saying goodbye to 6V..

I can't think of many reasons why we haven't moved up to say 24, 36 or even maybe 48V.

I mean wiring costs, less weight, loom size, better connections, smaller connectors, lower amps, led lights are easily adaptable, etc are all upsides.

Seems like a good time in the industry to put it on the table.

[rebelrouser]

I have been waiting for the OEM to design an electronic camshaft, using solenoids for variable lift and duration, when I talked to a couple engineers they said 12 volts was not enough. Several years later we have diesels using paired injectors to develop over 100 volts using voltage inductive spikes of the non injecting paired injectors, so they did not need any more than 12 volts with this technology. And other engineers have told me they keep making electrical components that draw less and less amperage and voltage. So that is the reasons they have given me. They still have not gotten around to an electronic camshaft.

[emsvitil]

With lead-acid, part of the problem is cell balance.

You're more likely to get an out-of-balance cell when you have 12 cells (18,24..) than with 6 cells.

It wouldn't take as long for there to be some undercharged, and some overcharged cells and then get premature battery cell failure.

[Racer71]

We did some hvac testing on a large van was similar to a sprinter van when I was a fabrication at visteon that was 48v. The body work had all the usual masking for a prototype. Our chassis dyno was in a climate controlled room so we could get it super hot and also very cold for hvac functional testing and validation. Always wondered what became of the van, I wasn’t on that job so I never did ask who the manufacturer was. We were a ford spin off, but I did prototype work for Long Engineering, Daimler, C&R, Chrysler etc during my time there.

[Nefario]

I mean wiring costs, less weight, loom size, better connections, smaller connectors, lower amps, led lights are easily adaptable, etc are all upsides.

I've done a lot of mechanical packaging of electronic equipment and this statement sounds like it comes from an electrical engineer! My thoughts...

- wiring costs, less weight, lower amps - Not really. Durability and handling strength in assembly may be more important. Most cost comes from the harness fabrication process.
- loom size - Again, using say 48V and 20-gauge wire leads to tiny delicate wiring. Loom size is generally not a problem now.
- better connections, smaller connectors - ANY commercial connectors are theoretically gas-tight at the contact level, increasing voltage to "clean" the contacts should not enter into the design. And do you really want to handle smaller connectors for say <10 wires?
- led lights - single LED's are generally set up for 5V each with a current limiting resistor so they're wired as needed already.

A lot of technology evolves until maturity and then stays there. Most wheels have 5 lugs, most gear selectors are in the console. Virtually all IC car batteries are lead acid. The current wet lead-acid battery has the "right" energy density versus number of internal components versus the inherent 2.1 volts of each cell.

With that said, the next generation of forklifts is using lithium-ion packs up to 48 volts for some of reasons you mention but mostly for quicker charging and higher energy density. Maybe we'll see it in automotive markets that can accept a special battery.

[peejay]

There used to be all sorts of talk in the trade magazines about the 42 volt future. (This would be a nominally 36 volt battery and a 42 volt alternator, or 3 times our current 12/14v systems)

It would allow electric A/C compressors, electric power steering, and there was talk of 100% electric brakes - you bolt up the corner of the suspension on the assembly line, plug in a connector, and go.

Well, as it turns out, electric power steering isn't that hard to do with 14 volt systems once you get over the idea of running a 30-80 amp motor (at 14v) to turn a hydraulic pump.

Electric A/C compressors are a neat idea as far as plumbing goes - the theory was that you could bolt the compressor to the chassis and run all of the refrigerant plumbing in hardline. As it turns out, we have them today (well, 10-20 years ago) with 200-300 VAC hybrid systems, and everybody bolts the electric compressor to the engine because electric A/C compressors are high in NVH. Bolting to the engine solves that problem since the engine is already fairly well isolated from the chassis. High quality hoses are cheaper than trying to isolation-mount the compressor to the chassis... and you'd need hoses ANYWAY to keep the NVH from being transmitted through the hardlines. (Same reason why many cars have flex hoses going to the ABS unit - cut NVH transmission when the ABS is working)

100% electric brakes - HA. Not happening. Hell we have the capability now , and have had for quite a long time, for 100% electrically actuated brakes, and all such systems in production have a hydraulic interlock so that if the electrics fail, the brake pedal is still physically connected to at least two calipers.

In short, there is no reason to change.

[LoganD]

The honest truth? The old people in the industry are resistant to change. OEMs never want to take the R&D and validation hit on changing tech, so they sit around and wait for someone else to do it.

48V is already here, and it will soon take over. Anyone who says otherwise clearly doesn't work in the OEM field.

[peejay]

Turn the question around: What are the advantages of higher voltage?

Wiring and connectors are already so small (thanks to networking everything) that handling causes most of the wiring issues. There are diminishing returns in going to higher voltage just so that you can reduce the size of the wire going to the defroster grid by .8mm.

ABS units are already just about the size of the valves and the control board. Window motors and other motors are basically mostly geartrain. EPAS is easily done on 14v, in ways that are probably actually cheaper to produce since they are putting the electric unit where a RHD rack's pinion would be, and presumably vice-versa in RHD models.

What is the overarching need to move away from 12v? We moved from 6v for better ignition systems and less current draw on the starter.

We haven't moved from 12v because it still works just fine. When we need more, we either go straight to three phase AC voltage, or in the case of piezoinjectors, we use step-up circuitry that is necessarily complicated not for the increase in voltage, but because we also are actively closing the injectors with ringback. Even with higher system voltages, we're still going to need that capability if we want fine injector control (and we do).

So, again, what are the advantages that would justify having to re-engineer literally every component in a given car?

[LoganD]

They re-engineer the parts every few years anyway. An ABS module from 2010 isn't the same as one from 2019, so it's not a big deal to change the voltage.

The advantage is better in-car automation. Active roll bars, active dampers, knock detection systems, etc all become easier with higher voltage. Even something like a VVT system has more possibilities.

[F-BIRD'88]

I have been waiting for the OEM to design an electronic camshaft, using solenoids for variable lift and duration, when I talked to a couple engineers they said 12 volts was not enough. Several years later we have diesels using paired injectors to develop over 100 volts using voltage inductive spikes of the non injecting paired injectors, so they did not need any more than 12 volts with this technology. And other engineers have told me they keep making electrical components that draw less and less amperage and voltage. So that is the reasons they have given me. They still have not gotten around to an electronic camshaft.

The electrics/electronics is better used in controlling the (dedicated) hydraulics of a hyd valvetrain to achieve variable valve duration. G;v;ng away secrets here.
Don't got my patents (yet) so... But many are sniffing around my design.
Hint: get the hydraulics out of the lifter in the system.
I talk too much...

[peejay]

They re-engineer the parts every few years anyway. An ABS module from 2010 isn't the same as one from 2019, so it's not a big deal to change the voltage.

They don't re-engineer everything to that extreme of a degree, though. There's always going to be legacy hardware.

At any rate, this isn't the kind of engineering I'm talking about. I mean the type of things they would have to do to ensure that absolutely nothing from a low voltage system is used in a high voltage system. Especially as it would be prohibitively expensive to do a 100% roll-in, so there would be legacy systems in place that would have to run on their own separate buses.

I can't think of a single vehicle made that started life 100% fresh, with no shared components with other or previous models. That's the sort of thing that would have to happen with a voltage change. It was not terribly difficult in the 50s and such, when you had negligible electrical components and the "electronics" was your kid's ham radio riding in the back seat.

[Belgian1979]

I know that Audi was considering this. One of the reasons was the use of electric turbo's for low rpm use.
Can imagine that it'll be a balancing act of a larger battery vs reduced weight in wiring etc.
Don't know where they are now. Maybe with the planned move to electric cars this is less of a priority at the moment.

[Geoff2]

I think it is inevitable that a higher voltage will come into use, simply because of the increasing use of electrical components in new cars. Solenoids & motors are being used in increasing numbers for things such as valve control, electric steering etc. These require, relatively, a lot of power.
Using say 24 or 36v would allow thinner & lighter wire to be used, a saving in weight & cost.

[Belgian1979]

With can communication controlling almost everything I think reducing weight by reducing the number of wires is overstated.

[mk e]

Maybe with the planned move to electric cars this is less of a priority at the moment.

Winner!

I'm pretty sure they are just planning to run out the 12V systems until they kill fuel engines or at a minimum wait until all the bugs are worked out with the electric cars were customers will still tolerate more problems then roll it over.