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Tesla shares 48V architecture with other automakers

electrek.co

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Re: Tesla shares 48V architecture with other automakers

#471

Earlier quoted context omitted.

Watts = Amps * Volts (or, more scientifically, P = I * V) If something draws 48 Watts of power, you can either supply it with 4 Amps @ 12 Volt, or 1 Amp @ 48 Volt. It's the amps that determine how thick the wiring needs to be, so by lowering the amperage, you lower the amount of wiring needed. I believe the only reason cars are 12 V is because that's a practical voltage to build lead-acid batteries at (which is actua…

This makes such little sense to me. I'm probably just stupid, but if the same amount of power is flowing through the wire, don't you need the same size of wire? A higher voltage system will push more energy through the same component, so you need thicker wires. If you up the resistance of the component to consume the same amount of energy as before, you arrive at the same size of wire you were using before, don't you…

Imagine you've got an object you want to move by shooting water at it from a hose.

If the pressure coming from the hose is high, then you don't actually need a lot of water, and so you can use a narrow hose. On the other hand, if the pressure is low, you'll need to use a lot more water at once, so a wider hose.

It's the same thing for electrical components. If you'll excuse the mixed analogy, if you need to push an object with 480 watts of water to get it to move the speed you want it to, you can either do it with 48 volts of pressure with a hose 10 amps wide, or do it with 12 volts of pressure 40 amps wide.

Re: Tesla shares 48V architecture with other automakers

#472

Earlier quoted context omitted.

> 60 volts is nothing UNLESS you are completely wet or sweaty. Ha, it’s always easy to tell when people have experience with these things. Doorbell wiring is 48V. Go hold those in each hand and tell me how impossible it is to feel if your hands are dry.

Doorbell voltage in the US is typically 12V or 24V AC in the US. I can’t feel that with dry hands. You might be confused with POTS (landline phone service) which is 48V DC with all phones not in use.

Just don't be holding on when it rings! That's painful, with 90 VRMS at 20 Hz.

Re: Tesla shares 48V architecture with other automakers

#473
what I want to know... Is this really what the document looked like? Or was it artistic license for the video?

https://www.rivianownersforum.com/attachments/tesla-48v-jpg....

"How to Design a 48V Vehicle

You incompetent boobs!

Do we REALLY have to do your homework for you?

XXOO, Elon"

I saw this on https://youtu.be/L6WDq0V5oBg

Re: Tesla shares 48V architecture with other automakers

#474
post #460

Earlier quoted context omitted.

Re-read the comments, others have not done it. Audi has a mild-hybrid 48V (as do many others) that also runs some other things like active roll control and the power steering pump. They still have a 12v system running infotainment, seat heaters, defrosters, powered seats, lights, etc. etc.

As I never knowingly listen to music on 48V, is it reall so much better than 12V?

It's not about making the music sound better anymore than getting rid of an internal combustion engine is about getting you there faster. Have you ever seen the size of the wires in a car that go the amplifiers? They're as thick as your thumb.

The move to 48V means much less power is lost (power loss = (IxI)xR ), cables can be much smaller, cables and terminals can be much lighter and much less copper can be used used.

Basically it's just a more efficient way of doing things.

Re: Tesla shares 48V architecture with other automakers

#475

Many comments here seem to be confusing the accessories circuit voltage with the electrical vehicle motor and drive system. The vehicle motors have a combined power output of 450KW which requires a high voltage 800V system or the wiring would be so heavy it would not be feasible. This spec appears to be the accessories circuit with Tesla pushing for a new 48V standard. That’s super smart because it immediately means…

Dumb question but why does deciding to run at a higher voltage decrease the amount of wiring necessary? And why not increase it even further then?

[deleted]

Re: Tesla shares 48V architecture with other automakers

#476
post #374

Earlier quoted context omitted.

> but there are probably reasons it hasn’t already changed everywhere else Yes, the legacy OEMs are constrained by their suppliers, who dictate what they can (not) do.

In automotive, it is usually the other way round. Regardless, what exactly was wrong with the existing 12 and 24 V systems for auxiliaries that absolutely needed to be changed?

> what exactly was wrong with the existing 12 and 24 V systems for auxiliaries that absolutely needed to be changed?

The same thing that was wrong with vehicles that get 10mpg.

The same thing that was wrong with laptops that get so hot they burn your lap and the fan sounds like a jet engine.

The same thing that was wrong with incandescent bulbs getting hot instead of using that energy for light.

This is about making things more efficient.

Re: Tesla shares 48V architecture with other automakers

#477

Earlier quoted context omitted.

It was never worth it to retool for decades ? Or was there a pathological lock-in between suppliers and manufacturers that prevented even the most obvious innovations from happening if they required any amount of coordination?

24V is common in trucks, and yet never made it to regular cars because there was never sufficient reason. Using a higher voltage is not an innovation (it's an obvious change, and we've gone from 6V to 12V to, in some cases, 24V already) - rather it's just a slight efficiency improvement in largely non-critical systems, with not a lot of incentive to take on the cost of transition. In a a personal ICE vehicle, the onl…

The 12v battery performs the very significant safety feature of allowing the HV battery to be disconnected when the car isn’t ready to move. You’d need to have a converter in the HV battery to avoid that down side, and then you have a new downside of a fault could cause your 12v line to be HV instead.

Re: Tesla shares 48V architecture with other automakers

#478

Earlier quoted context omitted.

Yes but state of your body/skin (R) and current (I) is what matters with regard to 60 volts being really dangerous (also the current path as the article below states). 60 volts is nothing UNLESS you are completely wet or sweaty. "It is estimated at 150 ohms for completely wet skin (in water), 1000 ohms for sweaty skin, and 100,000 ohms to 500,000 ohms for dry skin." Assuming a worst-case scenario with dry skin provid…

> 60 volts is nothing UNLESS you are completely wet or sweaty. Ha, it’s always easy to tell when people have experience with these things. Doorbell wiring is 48V. Go hold those in each hand and tell me how impossible it is to feel if your hands are dry.

What you stated is incorrect. Anyway, V=IR is a truth. If you touch 48v DV dry. You are going to be fine.

Re: Tesla shares 48V architecture with other automakers

#479
post #277

Earlier quoted context omitted.

Are we not all still buying multiple packs of AA batteries every year? Or maybe it's just those with kids.

Oh I hope nobody's doing that, rechargeables have been so good for so long. I'm just now retiring some that I bought in the 2007-2011 timeframe which have started to fail, but my 2015 purchases are still going strong with hundreds and hundreds of charge cycles on 'em. I haven't used alkalines since the 80s.

I have not had great luck with rechargeables. They have a lower voltage than regular AA, so I find that most sensitive electronics just start out thinking the battery is already low and then stop running before the battery is fully discharged. My Z-wave keypad lock is one of those. AA batteries last about 2 months, rechargeables start giving a low battery warning after a week and hardly last 2-4.

Re: Tesla shares 48V architecture with other automakers

#480
post #83

The "expert" in the article got it wrong. The relationship between the voltage and the losses in the wires is not proportional. They are squared. Going from 12V to 48V is not a saving of 4x rather 16x. For some applications you could also consider Power over Ethernet in the car, get both shielded comms and power. Or can and power over twisted pair.

> Or can and power over twisted pair. I was reading an anti-Musk subreddit over on Reddit and I think the cybertruck is doing this? They were mad that the cybertruck uses 48V and Ethernet cables, but to me, that seems perfect for CAN and power. We already use 48V (or similar) for PoE, and CAN needs a twisted pair... so why not buy that off the shelf instead of using a custom wiring harness? I don't think the cybertru…

Have a reddit link?. Search didn't help
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