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To Power the Future, Carmakers Flip on 48-Volt Systems

nytimes.com

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Re: To Power the Future, Carmakers Flip on 48-Volt Systems

#51

Post by kalleboo »

hinkley wrote: post #37
saltcured wrote: post #6

Earlier quoted context omitted.

You want a higher voltage to allow more power without huge cables due to high current. You want low voltage to avoid high-voltage safety issues which increase engineering, assembly, maintenance, and emergency costs. The 48V system sits right at the boundary where you can deliver enough power for more auxilliary systems and some mild-hybrid techniques including frequent start/stop systems, brief acceleration boost, an…

At 48 volts you start running engine accessories off of the electrical bus instead of belts and pulleys. That means the engine isn't necessarily responsible for keeping everything under the hood running at all times. You might not need a water pump or the AC when the engine is off, except to keep the cabin comfortable. But you still need things like power steering and power brakes, stability control and other safety…

> You might not need [...] the AC when the engine is off

Or you might! Driving a car with a start-stop system in the summer, it doesn't stay stopped at a red light for long until the AC wants to kick in and the engine comes back on.

Re: To Power the Future, Carmakers Flip on 48-Volt Systems

#52

Post by kalleboo »

twic wrote: post #11
sowbug wrote: post #8

Earlier quoted context omitted.

Thanks. I had always understood PoE's relatively high voltage as helping deal with the attenuation from long runs of thin copper wire. I couldn't find a succinct explanation in the article why cars would benefit from this spot in between merely sending information (digital levels like 1.8, 2.2, 3.3, 5.0, etc.) and using electricity to do "real" work (120V, 240V, 480V, etc.). As I understand your answer, yes, they'd l…

The specific number of 48V is presumably inherited from telecommunications: https://electronics.stackexchange.com/questions/10851/why-do... There's lots of telecom equipment that works at 48V, so it's presumably cheap and easy for carmakers to find suppliers.

I would have assumed it's just because it's a multiple of the current 12V (so you could use shortcuts like wiring 4 existing 12V lamps in series)

Re: To Power the Future, Carmakers Flip on 48-Volt Systems

#53

Post by solarkraft »

phkahler wrote: post #23
mcguire wrote: post #13

About a decade ago, wasn't there some interest in moving to 24 volt systems; nothing came of it due to switch failures, IIRC?

It's always been 48V. The problem has been a chicken and egg sort of thing. Its expensive to have both 12 and 48, but you can't go full 48 unless you can source all components for that voltage. Suppliers didn't really commit because there were no real customers.

How hard is it to put a DC-DC converter between the systems?

Re: To Power the Future, Carmakers Flip on 48-Volt Systems

#54

Post by mseebach »

nimbius wrote: post #38
csours wrote: post #34

> "But skeptics may wonder why engineers are devoting so much effort to developing the mild hybrid systems that could be seen as stopgap measures on the path to a fully electric vehicle fleet." Let's do some napkin math. Assumptions: 1. Gasoline will never exceed $10/gallon. (assumes eventual plant/algae sourcing/some kind of magic). 1a. Vehicles achieve 50 mpg (2 gallons/ 100 miles) via tricks like 48-volt. Thus fut…

>Gasoline will never exceed $10/gallon. The consequences and repercussions of global warming and climate change plus Nixon era doctrine of interventionalist policy in the interest of maintaining global US oil hegemony have easily put real barrel cost easily above this. Iraq didnt pay for itself twice, after all.

There's plenty, like a lot, of shale oil available at $80-100/bbl, which allows for significantly less than $10/g gas.

The only meaningful challenge to $10/g gas is policy (ie taxation).

Re: To Power the Future, Carmakers Flip on 48-Volt Systems

#55

Post by lafar6502 »

_ph_ wrote: post #46
csours wrote: post #34

> "But skeptics may wonder why engineers are devoting so much effort to developing the mild hybrid systems that could be seen as stopgap measures on the path to a fully electric vehicle fleet." Let's do some napkin math. Assumptions: 1. Gasoline will never exceed $10/gallon. (assumes eventual plant/algae sourcing/some kind of magic). 1a. Vehicles achieve 50 mpg (2 gallons/ 100 miles) via tricks like 48-volt. Thus fut…

The big error in your calculation is, that you calculate only the cost of the battery, but not the cost reduction of removing the most complex parts of a combustion engined car: the engine itself, the gearbox and the whole exhaust system including cleaning. If you calculate this in, you should come up with very different numbers - a lot of experts think, that electic cars might be even cheaper to buy in the early 20i…

So far electric cars cost more than ICE including this cost reduction

Re: To Power the Future, Carmakers Flip on 48-Volt Systems

#56

Post by lafar6502 »

nimbius wrote: post #38
csours wrote: post #34

> "But skeptics may wonder why engineers are devoting so much effort to developing the mild hybrid systems that could be seen as stopgap measures on the path to a fully electric vehicle fleet." Let's do some napkin math. Assumptions: 1. Gasoline will never exceed $10/gallon. (assumes eventual plant/algae sourcing/some kind of magic). 1a. Vehicles achieve 50 mpg (2 gallons/ 100 miles) via tricks like 48-volt. Thus fut…

>Gasoline will never exceed $10/gallon. The consequences and repercussions of global warming and climate change plus Nixon era doctrine of interventionalist policy in the interest of maintaining global US oil hegemony have easily put real barrel cost easily above this. Iraq didnt pay for itself twice, after all.

Why everyone talks about switching to electric cars while nobody ever mentions electric heating of buildings as environmentally friendly alternative? Because it isn’t? Why bother with electricity-saving lightbulbs while EV owners burn the current like there’s no tomorrow...

Re: To Power the Future, Carmakers Flip on 48-Volt Systems

#57

Post by _ph_ »

lafar6502 wrote: post #55
_ph_ wrote: post #46

Earlier quoted context omitted.

The big error in your calculation is, that you calculate only the cost of the battery, but not the cost reduction of removing the most complex parts of a combustion engined car: the engine itself, the gearbox and the whole exhaust system including cleaning. If you calculate this in, you should come up with very different numbers - a lot of experts think, that electic cars might be even cheaper to buy in the early 20i…

So far electric cars cost more than ICE including this cost reduction

That is correct. Most car manufacturers currently pay way more than $100 per kWh battery capacity. Also, the electrical vehicles are made in much smaller numbers than combustion engined ones, raising production costs considerably. But for a long-term calculation, you cannot ignore the cost savings of leaving off all the combustion-related technologies. And that there are significant cost savings should be obvious.

Re: To Power the Future, Carmakers Flip on 48-Volt Systems

#58

Post by phkahler »

solarkraft wrote: post #53
phkahler wrote: post #23

Earlier quoted context omitted.

It's always been 48V. The problem has been a chicken and egg sort of thing. Its expensive to have both 12 and 48, but you can't go full 48 unless you can source all components for that voltage. Suppliers didn't really commit because there were no real customers.

How hard is it to put a DC-DC converter between the systems?

That's technically and conceptually easy but it costs a lot of money. One approach would be to put a large DC-DC converter on the car and run a 48V bus next to the 12V one. That's a very expensive device, needing to be perhaps a few kilowatts depending which devices are on 48V. It's also a lot of extra wiring, and the need to manage the extra variations in vehicle systems.

A second approach would be to put a DC-DC converter only in the devices that need 12V. But that's asking every supplier to change their design to accommodate 48V and the vehicle manufacturers will bitch about the cost increases. It'll be a moderate increase across a LOT of devices.

I'm working on a product that uses a highly integrated SoC that has all the regulators needed to connect it directly to the 12V line (it'll run on 6-20V or so). It even has an on-board 5V regulator for additional off-chip devices. The best thing for us would be if the same chip existed but could be connected directly to 48V (not sure what the range is on that) but from a silicon standpoint there is a big difference as well. Adding an external regulator would add cost, and invalidate some of the wake-up features and low current standby capabilities of the chip.

There are always "reasons". The only way to make the transition is for someone to make it happen, but again the suppliers who participate may be seeking premium pricing in the beginning because there aren't options.

Re: To Power the Future, Carmakers Flip on 48-Volt Systems

#59

Post by vinay427 »

csours wrote: post #35
csours wrote: post #34

> "But skeptics may wonder why engineers are devoting so much effort to developing the mild hybrid systems that could be seen as stopgap measures on the path to a fully electric vehicle fleet." Let's do some napkin math. Assumptions: 1. Gasoline will never exceed $10/gallon. (assumes eventual plant/algae sourcing/some kind of magic). 1a. Vehicles achieve 50 mpg (2 gallons/ 100 miles) via tricks like 48-volt. Thus fut…

Replying to myself: One thing the above does not take into account is the feeling of a BEV, which internal combustion and weak hybrids simply cannot match. I deeply feel that luxury customers will demand strong electrified powertrains after experiencing them. Strong hybrids could match the feeling of a BEV, at a similar per-unit cost. One issue is engineering and certification costs - manufacturers can only do so muc…

> One thing the above does not take into account is the feeling of a BEV, which internal combustion and weak hybrids simply cannot match.

I absolutely agree about most luxury customers. However, there are certainly those of us in the minority who favor a more mechanical experience when driving a car, and most electric cars seem to move even further away from this in pursuit of efficiency, etc. Consequently, I don't think this market will exist for much longer once driving becomes more commoditized.

I'm certainly on a tangent by now, but there an interesting piece by Malcolm Gladwell in Car and Driver about a possible result of the rise of autonomous cars on car culture today: www.caranddriver.com/features/when-autonomous-cars-rule-what-will-happen-to-car-culture-feature

Re: To Power the Future, Carmakers Flip on 48-Volt Systems

#60

Post by csours »

_ph_ wrote: post #46
csours wrote: post #34

> "But skeptics may wonder why engineers are devoting so much effort to developing the mild hybrid systems that could be seen as stopgap measures on the path to a fully electric vehicle fleet." Let's do some napkin math. Assumptions: 1. Gasoline will never exceed $10/gallon. (assumes eventual plant/algae sourcing/some kind of magic). 1a. Vehicles achieve 50 mpg (2 gallons/ 100 miles) via tricks like 48-volt. Thus fut…

The big error in your calculation is, that you calculate only the cost of the battery, but not the cost reduction of removing the most complex parts of a combustion engined car: the engine itself, the gearbox and the whole exhaust system including cleaning. If you calculate this in, you should come up with very different numbers - a lot of experts think, that electic cars might be even cheaper to buy in the early 20i…

You are correct, it is napkin math after all. Assuming similar sales between mild hybrids and BEVs, the eventual cost of a BEV is probably only $2,000 to 3,000 more in the short term... but consumers make decisions based on differences $500 or even less.

I could do some more napkin math with engineering costs, unit costs, Bills of Material and amortization schedules... but you can be assured that automakers have done more than napkin math, and they are pursuing (as an aggregate group) both technologies.

The business cases for each of MHEV and BEV make different assumptions. I think it's great that different methods are being pursued. Eventually some automakers look very silly, but you can't tell which ahead of time.

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