>That is why it is supporting the move to higher voltage, to have smart >peripherals on a bus. Instead of trying to run half a dozen tiny wires to .> each lamp holder, it gets a power wire and a communication wire run to all, and each listens to their own address, so no tiny wires needed... Maybe...but then again now you've got a single point of failure too. If either the power wire or communication wire breaks, thenperhaps it's not just 1 little courtesy light that goes out, but entire back of the car stops., no lights, no trunk, no brakes, blah blah. I just would be wary about getting too in love with reducing copper and 48V and not seeing the big picture. I think critical systems should be treated differently than non critical systems. Having individual wires to tail lights is not a problem inmy opinion. LED lights already require tiny wires, so I don't see the big advantage in 48v 48V would be awesome for a trailer connection... Honestly I could see a more distributed system where the back of the car has it's own circuit breakers and relays but still keep last few feet as individual wires
On Sunday, October 6, 2024, 8:50:45 PM PDT, Cor van de Water via EV <ev@lists.evdl.org> wrote: That is why it is supporting the move to higher voltage, to have smart peripherals on a bus. Instead of trying to run half a dozen tiny wires to each lamp holder, it gets a power wire and a communication wire run to all, and each listens to their own address, so no tiny wires needed... On Sun, Oct 6, 2024, 8:36 PM Lawrence Winiarski < lawrence_winiar...@yahoo.com> wrote: > Good example and shows the same power loss, but I think carrying it a bit > further, you also need the wire to be able to deal with the power loss. > > In other words resistors are not just rated on ohms, but also watts. > > So it's not just about "efficiency" in terms of power loss, but it's also > about heat. > > In your example, it may be true that both wires waste the same energy, but > they also must absorb that energy. > > Bigger wires can dissipate 100 watts/foot no problem....But for tiny > wires, dissipating 100 watts/foot may prove a problem. > > Also for distribution lines, increasing the voltage and decreasing the > wire size means that the actual Electric field that must surround the wire > is going to get super intense not just > because of the voltage, but also because the wire is smaller. And this > also causes all sorts of problems with ionization. That's why instead of > having 3 wire for 3 phases, they > often little groups of 3 wires for each phase, because this simulates a > larger wire for the phase. > > Then also we have mechanical issues. A wire 1/4 the diameter is only > 1/16 as strong. 40 AWG wires might be adequate electrically, but the are > very fragile. > > Then we have corrosion issues. Higher voltages accelerate corrosion so > smaller wires at higher voltages will corrode faster. For the same > lifetime, you might even need thicker wires.. > > Not trying to be negative, but maybe just pointing out that things might > be a little more complicated. > > > > On Saturday, October 5, 2024 at 08:48:24 PM PDT, Cor van de Water via EV < > ev@lists.evdl.org> wrote: > > > Note that if you want to save on copper and are only interested in > delivering the same power with the same percentage of wire losses, then > going 4 times up in voltages allows you 16 (!) times smaller wire surface > area, because current is 1/4 but also 4 Volt loss in a 48V system is the > same percentage as 1V in a 12V car. So if you needed a 1/4" diameter wire > (2 AWG) in a 12V car then you only need 1/16" diameter wire (14 AWG) for > 48V to transport the same power with the same losses. > In different words: going up 4 times in voltage means you only need 6% of > the copper for the same performance. > Now you may get why distribution lines are so high voltage. > Cor. > > On Sat, Oct 5, 2024, 6:50 PM Lee Hart via EV <ev@lists.evdl.org> wrote: > > > >> On aircraft, 28 volts (24 volts) has been the standard low voltage > > forever. > > >> It is the standard on specialized military vehicles and equipment as > > well. > > > > Also in large trucks and buses. > > > > > "42 volts" is the threshold for "low voltage" in the US National > > Electrical > > > Code, but as I recall, that is for AC rather than DC. > > > > Yes, also UL and ETL. They specify 30vac or 42vdc peak as the maximum > safe > > limit for voltages you can touch. > > > > > I suppose if you are going to make a departure from the industry > > > standard of 12 volts, then why not go all the way to 48 volts. > > > > 48v actually exceeds the "low voltage" classification for NEC, UL, and > ETl > > etc. There is also a problem with arcing. Switch, relay contacts, fuses, > > circuit breakers, motor brushes, etc. are all typically limited to 30vdc > > max before arcing will not extinguish itself. > > > > To me, it makes more sense to increase vehicles from 12v to 24v, in line > > with a huge number of other vehicles. There are already lots of 24v > > accessories. Going to 48v means essentially no standard components or > > accessories can be used. > > > > That said... The auto companies routinely ignore electrical safety > > standards. They use undersized wire gauges, combustible wire insulation > > that melts at lower temperatures, inadequate fuses, switches and relays, > > etc. > > > > Lee > > -- > > Excellence does not require perfection. -- Henry James > > But it *does* require attention to detail! -- Lee Hart > > -- > > Lee A. Hart https://www.sunrise-ev.com > > > > > > _______________________________________________ > > Address messages to ev@lists.evdl.org > > No other addresses in TO and CC fields > > HELP: http://www.evdl.org/help/ > > > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20241005/991da995/attachment.htm > > > > _______________________________________________ > Address messages to ev@lists.evdl.org > No other addresses in TO and CC fields > HELP: http://www.evdl.org/help/ > > -------------- next part -------------- An HTML attachment was scrubbed... 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