15 ms·
Upping the volts will make hybrid cars much cheaper
- bsder 10y agoQuestion: Why not go to 96V? Everything wants to go higher for all manner of reasons, and the semiconductor switches probably don't care all that much. If the jump has to be made, make the jump as far as possible so that the jump doesn't have to be made again. Is there a safety reason or something?
- msandford 10y agoInertia and fear of the unknown. Also below 50V is generally considered "safer" and anything around 100 and up is "dangerous" due to the impedance of the human body.
- mixedCase 10y agoDangerous as in a bad kick, but it can't fry you like current AKA amps can (which is usually the worst part, which you want to avoid).
- deleted 10y ago[deleted]
- mindslight 10y agoThat's like saying that falling off a building can't kill you (because it's actually the stop that does). You lower the current by lowering the voltage.
- IanCal 10y ago> You lower the current by lowering the voltage. I assume you meant increasing there.
- Mchl 10y agoI = V/R So once the voltage is applied to your body, the higher it is, the more current flows through you (Some assumptions about source of electricity made)
- tempestn 10y agoIf you're talking about a controlled situation where you need to provide a given amount of power - ie driving the accessories of a car, then yes, a lower voltage would require higher current. P = IV When you're talking about safety though, the issue is what happens if the voltage gets applied to your body. In that case the relevant formula is I = V/R. R is the resistance of whatever circuit you've mistakenly formed through your body. The higher the voltage applied across that circuit, the higher the current that will flow. (This is also why it's more dangerous if you're wet, or in bare feet, for instance, because those things lower your resistance, resulting in greater current for a given voltage.)
- seanp2k2 10y agohttps://learn.sparkfun.com/tutorials/voltage-current-resistance-and-ohms-law/voltage https://learn.sparkfun.com/tutorials/voltage-current-resista... looks like a good resource if anyone reading this has no idea what we're talking about. Don't feel bad, we were all beginners once :)
- simcop2387 10y agohttps://www.youtube.com/watch?v=XDf2nhfxVzg https://www.youtube.com/watch?v=XDf2nhfxVzg Current and Voltage are intimately related. 1V with a 1kA capable supply will not hurt you.
- theatrus2 10y agoSemiconductors care a lot. There is a sweet spot in the <= 48V range, and even more in the <= 24V range. High voltage devices are much harder to miniaturize, and the conversion ratios for the inevitable logic supplies can be done a lot cheaper at lower voltages. Safety is of course a huge component. 48V is about the limit before special isolation and insulation is required.
- mindslight 10y agoTrunk full of rackmount telcom gear for IoT, duh. There actually is an existing sweet spot for 60V FETs, optimized for traditional 48v power systems. I've got to wonder if they're going to use -48v to allow simple driving of N FETs, or if the ubiquity of modern high-side drivers has made that a moot point.
- drzaiusapelord 10y ago48V is the threshold before you're regulated as a high voltage device. That means all sorts of safety standards, larger or less efficient electronic components, risk of injury, etc which translates directly to cost, risk, weight, etc.
- Grishnakh 10y ago>Question: Why not go to 96V? >and the semiconductor switches probably don't care all that much Yes, actually they do. Power MOSFETs are usually in the 30-60V range. When you go higher than that, costs go way up and you generally need to switch to IGBTs. MOSFETs capable of switching 30V loads at extremely high loads (like 100A) are dirt cheap. Power devices capable of switching 100V are not.
- IshKebab 10y agoAnything under 50V is considered "low voltage".
- iaw 10y agoI'm seriously waiting for auto-makers to pull their heads out of their asses and start putting kinetic energy capture systems into every car, economy to performance. The absurdly priced Porsche 918 is the only car to date that takes advantage of this technique in an ideal fashion (small batteries, small electric motors augment the engine and brakes). After that, what about ICE's that run at optimal load/RPM for the highest possible efficiency to charge a smallish electrical system? Batteries are still a long way off from gasoline in their energy density. Gasoline will never be "clean" but the way we burn it in our existing automotive fleet is horribly inefficient. There's this beautiful middle ground in the technology that no one is exploring and it's such a shame.
- thomas11 10y agoIsn't the Chevrolet Volt what you describe in your third paragraph?
- joezydeco 10y agoOr Mazda's i-ELOOP?
- iaw 10y agoNope, the Mazda i-ELOOP system scavenges waste kinetic energy to run only the electrical system as opposed to augmenting propulsion. It's a step in the right direction but is a 5% efficiency gain opposed to a 50% gain.
- beamso 10y agoBMW i3 REX as well.
- iaw 10y agoClose, except for they lobbed a motorcycle engine into an electric car and called it a "range-extender" but the engine can't generate power to meet maximum demand of the car's electrical system. So, instead of putting the motorcycle engine in as an afterthought take a 1.5l turbo as the primary source of electricity generation.
- manicdee 10y agoThis article is seriously confused. Current BEVs use 400+ Volts for the motive power, but still have 12V for accessories due to the established market. Increasing to 24V or 48V means less current for the same load, which means smaller cables for accessory power. Above 30V or so you get into "high voltage" by electrical safety standards. A 48V electrical system is not going to be driving hybrid vehicles, it is purely to reduce the cost of wiring looms.
- TorKlingberg 10y agoI have always heard that <50V is considered low voltage by electrical safety standards, which is why 48V is a good choice.
- dfox 10y agoFor electrical safety, <50V DC is common definition for ELV. For some (probably business oriented, ie. to do price differentiation for telco equipment) reasons, some electronics manufacturers classify anything over 30V as high voltage.
- asmithmd1 10y agoThe US National Electric code defines <50V as low voltage but UL defines anything over 20V as high voltage. UL generally deals with products so that is probably why they are more conservative. Picture a baby sucking on something and you can imagine why they want anything over 20V to be double insulated. If car manufactures want to comply with UL standards that would mean they would no longer be able to use the car's frame for the current return path.
- IshKebab 10y agoYeah I've always heard that. I just looked it up and it's actually 75V DC in the EU, and 50V AC. http://ec.europa.eu/growth/sectors/electrical-engineering/lvd-directive_en http://ec.europa.eu/growth/sectors/electrical-engineering/lv...
- agoetz 10y ago
- kevhito 10y agoEven the opening sentences are wrong: > VOLTAGE is to electricity what pressure is to water: the more you have of it the more oomph you get. That is why electrical power lines work at high voltage. No. Losses in transmission lines are proportional to current squared [1]. High voltage is used because it results in lower current (for the same power), so lower losses. [1] http://www.bsharp.org/physics/transmission http://www.bsharp.org/physics/transmission
- pietjepuk88 10y agoI think the analogy holds up quite well, even though they don't go into the details that you mention. Losses in water transmission lines for example are also proportional to velocity squared.
- seanp2k2 10y agoVoltage is how hard the nozzle sprays, current is the diameter of the hose. High pressure + small hose can be as much flow as a fire hose just gurgling out. Correlates well to how much current a given wire gauge can handle as well. If you hook the garden hose up to a fire hydrant and open it up, the garden hose might explode since it can't handle all the water. A pressure washer might use a thin hose, but the water sprays so hard that it can cut your skin. Idk, that's how I learned it growing up before I learned about stranded vs solid core wire, skin effect, resistance, etc.
- tbrownaw 10y agoOnly if you take the wire gauge as fixed. If instead you use the cheapest (smallest) you can get away with, you'll find yourself using smaller wires at higher voltages, with higher resistance and so less then quadratic loss reduction.
- bjt2n3904 10y agoPerhaps a way to help understand this. Power delivered by the battery is this equation: P = I * V So you can have (1 volt @ 100 amps), or (100 V @ 1 amp) and still get (100 watts). If both are the same, wouldn't the low voltage solution be safer, and more desirable? Massaging the same equation a little bit, we can model our losses along the power lines. Substituting V = IR you get... P = (I^2)R It's difficult to make conductors less resistive without using expensive metals or unconventional techniques (like cryogenically cooled wires). So to cut our losses, we'll go with high voltage, low current.
- sandworm101 10y agoThis is not the first 48v debate. Several years ago is came and went over the desire for electric brakes, solenoids rather than hydraulic calipers. They would theoretically be cheaper and simpler to manage electronically. 48v or higher would be needed for such things (also for running AC pumps). But brakes are very established and mature tech. They are also the primary safety system. Antilocks work well enough as is. Manufacturers balked at the idea of starting from scratch with purely electric brakes. With the need for higher voltages mooted, the debate came and went. Anyone worried about hacking cars, imagine the nightmare should brakes be completely electric, with no hydraulic or mechanical option should either the power or control system fail. As for saving weight on cables, smaller metal doesn't mean smaller cables. Higher voltage would require greater shielding, thicker cables. The increased risk of sparks/shorts would also be a thing, as would the risk of electrocuting those working on their cars. With 12v you can get away with stuff that at 48v might put you in hospital.
- ollie87 10y agoSurely any electric brake would fail closed? Just like air-brakes on large trucks. That would make them safer right?
- cmdrfred 10y agoAs long as actually fails yes, if the switch on the break pedal fails open for example you'd be in a world of hurt. I see where mistakes being made.
- bigtech 10y agoThey don't have to be perfect -- they just have to fail less often than current technology.
- deleted 10y ago[deleted]
- peterwwillis 10y ago
- snarfy 10y agoA shock from 50V DC can be fatal. This is more a cost cutting measure than a feature. Instead you lose a feature: safety.
- cnvogel 10y agoIt would be very hard to get several mA of current through your body from only 50V. That's why up to 50V is generally consisted safe low voltage which is not harmful to touch.