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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

#31

Post by GeorgeTirebiter »

dogma1138 wrote: post #16
maxerickson wrote: post #5

Earlier quoted context omitted.

The higher voltage means lower amperage, which means smaller components and so on.

You can use thinner cables or have the same cables with less loss. As for actual component size it’s not that simple the higher the voltage the more clearance you need between conductors. So that is bigger airgaps in PCBs and higher rated insulation where gaps aren’t possible.

True, however, this can also be achieved by different insulating materials. In general, this is not really much of a problem; I agree, it needs to be considered.

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

#32

Post by askvictor »

bigiain wrote: post #27
madengr wrote: post #24

Earlier quoted context omitted.

I think it’s 50 VDC that is considered HV. Any equipment we buy at work 50 VDC and over requires NRTL (i.e. UL) certification. Also interlocks and safety boxes when working on circuit.

I have no actual knowledge here beyond the article itself: “Why 48 volts? Settling on this level holds the electrical system under the 60-volt safety threshold of what is considered high voltage, where power cables must be orange and special connectors, costing 10 times as much, are required, said Mary Gustanski, chief technical officer of Delphi Technologies.” I wonder if your 50VDC limit is driven by the same “typi…

When I was studying electrical engineering, we were taught that at 30V, current may be able to pass through the skin (depending on a number of conditions presumably). Once it's under the skin, you only need a tiny current through the heart to kill you.

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

#33

Post by klodolph »

ggm wrote: post #25

This article conflates two things. One: adoption of a 48v standard for powered systems because it's a sweet-spot for efficiency, current draw, systems design. Two: PHEV and the adoption of electric transmission and drive train, which permits a non throttled engine of any form to run at constant high efficiency or not at all and use batteries. Two things. One story. Cars are becoming like common rail deisel with a uni…

The 48 V DC "sweet spot" is mostly safety / regulatory. As soon as you get to 50 V, the safety requirements (NEC) change. You can hold on to bare conductors with a 48 V potential across them just fine, even though 120 V AC will kill you and make it hurt the entire time you are dying.

48 V devices can require connections that are inconvenient and large, depending on what you want to power with them. Try running an air conditioner off 48 V and measuring the peak current draw.

https://electronics.stackexchange.com/questions/267789/how-s...

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

#34

Post by csours »

> "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 future gasoline MHEV vehicles cost 20 cents/mile to power, so $20 per 100 miles

2. Batteries get stuck at about $100/kWh. (maybe lithium etc never scales) 2a. Consumers are satisfied with 60 kWh batteries.

Thus BEVs cost $6000 more than comparable MHEVs (napkin math)

4. Electricity costs $0.20/kWh (assume some surcharge for the charging station). 4a. Your BEV gets 34 kWh / 100 miles (99 MPGe)

Thus to power your BEV costs $6.8 / 100 miles.

5. The difference between 20 and 6.8 is 13.2 - so you are paying off your battery at $13.2 / 100 miles. 6000/13.2 is about 450

---

Conclusion: It will take 45,000 miles to pay off your battery, assuming the competition is a 50 mpg vehicle and gasoline is $10/gallon.

Additionally, the initial cost for a BEV is $6000 higher, which is quite significant for entry-level buyers.

---

With 33 mpg and $5/g you have $15/100 mile, thus a 80-90,000 mile payoff.

With 33 mpg and $3/g you have $9/100 mile, thus 270,000 mile payoff

With 33 mpg and $2/g you have $6/100 mile, and you will never pay off the battery investment.

With 20 mpg and $3/g you also have $15/100 mile = 90,000

---

Home Solar: add $10,000 to your battery = $16,000

50 mpg and $10/g you have $20/100 mile = 80,000 mile payoff

33 mpg and $ 5/g you have $15/100 mile = 107,000 mile payoff

33 mpg and $ 3/g you have $ 9/100 mile = 179,000 mile payoff

33 mpg and $ 2/g you have $ 6/100 mile = 267,000 mile payoff

20 mpg and $ 3/g you have $15/100 mile = 80,000 mile payoff again

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

#35

Post by csours »

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 much at once or else shareholders get anxious.

Also not included are warranty reserves (how much to set aside per vehicle for warranty costs). More complicated vehicles call for more reserves.

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

#36

Post by fyfy18 »

maxerickson wrote: post #2

This article is kind of weird. The push for 48 volt is mostly about secondary systems that need a lot of power and doesn't have much to do with "mild electric" or whatever it is implying. The 21 HP direct boost mentioned in the article is going to be for performance rather than running on electric, the vehicle comes with a 1 Kw-h battery (~5 minutes at full output).

The main advantage of a hybrid system is that the engine can run at a more efficient speed, which is independent of the power being delivered to the wheels. Say you are driving through a town, accelerating from stopped to 30mph then cruising in traffic, the engine will start shortly after you start to move, run at 3000rpm the whole time (or whatever is the most efficient speed), then cut off when you begin the cruise.

This is why automatic transmissions now often have 7 or more gears, as it allows the engine to run at a more efficient speed. A hybrid system in comparison is mechanically a lot simpler though: In a Prius the clutches, transmission and alternator have all been replaced by a simple mechanical device with fixed gears and two electric motors.

As for the battery the Prius has a 1.3kWh battery, but due to battery longevity (the system tries to keep it charged around 60%) only around 400Wh is actually available for use.

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

#37

Post by hinkley »

saltcured wrote: post #6
sowbug wrote: post #3

There is a TLDR for this article, but as far as I can tell it cannot be derived from the article itself. Will someone please explain why 48-volt systems are newly desirable in cars?

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 systems.

Also, you start getting economies of scale with all-electric car components that pull down the price of EVs over time, because they can use the same components.

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

#38

Post by nimbius »

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.

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

#39

Post by uncle_bob »

madengr wrote: post #15

48 VDC will be good for amateur radio and car audio. Specifically the power amplifiers for both.

Noise from high power motors will be the bane of all operators, even when the car just drives by. However the junk yard will soon be a good place to source 48v generators.

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

#40

Post by MrBuddyCasino »

klodolph wrote: post #33
ggm wrote: post #25

This article conflates two things. One: adoption of a 48v standard for powered systems because it's a sweet-spot for efficiency, current draw, systems design. Two: PHEV and the adoption of electric transmission and drive train, which permits a non throttled engine of any form to run at constant high efficiency or not at all and use batteries. Two things. One story. Cars are becoming like common rail deisel with a uni…

The 48 V DC "sweet spot" is mostly safety / regulatory. As soon as you get to 50 V, the safety requirements (NEC) change. You can hold on to bare conductors with a 48 V potential across them just fine, even though 120 V AC will kill you and make it hurt the entire time you are dying. 48 V devices can require connections that are inconvenient and large, depending on what you want to power with them. Try running an air…

> You can hold on to bare conductors with a 48 V potential across them just fine

Even with wet hands? I was under the assumption the unconditionally safe upper limit was around 24V.

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