There's a good chance your home operates at lower current levels than a Chevy Volt or a Nissan Leaf.
For automakers and their suppliers, that's a meaningful statement. For decades, automobiles have employed relatively small batteries with 12V electrical architectures. When the battery alone wasn't powerful enough, engineers augmented it with an alternator and a fan belt.
Mitsubishi's i-MiEV employs isolators from Analog Devices in its electrical architecture.
(Source: Mitsubishi)
But times are changing. Although most vehicles still use the old 12V architecture, a new breed of hybrids and electric cars is changing the landscape. Today's electrified vehicles employ big batteries with far higher voltages. Mild hybrids, for example, operate at 60V-80V. Full hybrids fall in the 85V-100V range. Plug-in hybrids range from 150V to 300V, and full electric cars check in at 300V or more. Amperages are running as high as 200A or more.
"As you move up the scale, the voltages and amperages continue to fly up, so that they can facilitate the electrification," Randy Sumner, director of global hybrid and electric vehicle business development for Delphi Automotive, told us. "We're moving from the 12V world up to 100V, 200V, 300V, and even higher. We have customers in the 500V to 600V range."
For engineers, that's a big jump. In many cases, the old switches, relays, wires, isolators, interconnects, and passive components cannot handle the bigger electrical load. Automakers are looking for new components designed to handle the higher voltages and currents.
"Most of us have 200A service in our homes, and that usually powers the whole house," Sumner said. "Now we're talking about power service of the same magnitude inside the car. It's really a huge change from where we've been."
I would imagine the high voltages would also come with higher potential safety problems. I would imagaine the higher voltages could be an issue in collisions.
Your imagination is correct, Rob. Even in non-accident situations, the use of higher voltages adds an additional layer of engineering, as Chuck points out, in the form of isolators. Supposedly, a high-voltage isolator fault was at issue in the recent Fisker Karma car which "died" when it was brought out to Consumer Reports's test track.
This is getting wild. I understood the capaciter style battery fell out of favor because of the potential of dangerous discharge. This brings us right back.
Trawickim had some interesting observations. The safety feature that disconnects the battery reminds me of the fuel pump shutoff switches on some cars. Even the 12 Volt batteries should have some means of disconnecting. I'm reminded of a car fire that was extingushed only to reignite because of a short in the wiring. The fire extinguishers ran out before the battery did and the car was a total loss. Some industrial machhines have an emergency stop button that kills all the power. If you adjust the nuts and bolts on your battery connectors, you can push them down onto the battery post with a twisting motion and they will lock into place. You can also pull them back off in case of an emergency. If you have side posts, oh well. Pete O.
The cables in question will be exposed to temperature extremes (0-100 F in ambient swing alone). The insulation of these cables will have to stand up to that, as well as engine heat, and do so for a design life of a decade or more. No cracking or degradation of the insulation will be acceptable.
For years now, the operating temperature requirements for electronics in the engine compartment has been the "old" MIL-spec range of -40 to +125 C! Vehicles are expected to start and run from a (very!) cold start near the poles, and also to operate fine with engine compartment temps way above boiling water. Typical IC engines are designed with optimal running block temp around 110C. Before jumping into the automotive industry some years ago, I had done a lot of extreme hi-rel electronics design (both MIL and CO-grade telecom and 911 call centers), and the auto requirements made that look easy!
Re the "wattage" comments: just because a relay is rated for X volts and Y amps does NOT imply a capability of controlling an XY-watt load! Switching devices have multiple ratings (especially with inductive loads like big motors): carrying capacity and interrupting capacity are only two of the parameters, and both may have separate limits for V, A, and VA.
I also remember that at least 20 years ago, the UNANIMOUS agreement in the auto industry was that the "ancient" (e.g. late 1950s) 12VDC (incidentally, it's really 13.8VDC nominal) would soon be replaced by "24V" or maybe even 40V batteries and alternators, for multiple reasons including reducing the weight of all that copper whose usage was going up rapidly as electronics took over more and more of the subsystems of the vehicle! I guess nobody remembered their basic physics (if they ever learned it); INERTIA applies to many areas, even the marketplace!
Oh, I forgot an important point: anither compelling reason for the very high current rating is for FAST CHARGING reasons (so-called "Level 3" or 30-minutes for a full recharge), not so much for running the motor(s), even for a racing vehicle!
In developing hybrid construction equipment, inverters are now using 800 VDC capacitors and the bus takes several minutes to reduce to a voltage that isn't deadly. So, future accidents are highly likely. However, you can't force a new technology without hazards especially when consumers need the new product to perform to the exact same specification as the traditional product.
I realize the article is about the shift to higher voltages in automotive electrical systems, but the "history" portion at the top of the article makes no sense at all, particularly this line: "When the battery alone wasn't powerful enough, engineers augmented it with an alternator and a fan belt."
There was never an automobile that included a battery but provided no means to charge it. Some very early ones had a magneto for the spark, a hand crank for starting, and carbide lamps for headlights, but as soon as the magneto was replaced with a coil-and-points ignition system, a generator was needed to charge the battery. In fact, some early vehicles had generator-driven electric lights before they had an electric starter or a battery.
Also, if one is writing a brief history of automotive voltages, it should be mentioned that all military vehicles since about 1950, and some heavy civilian vehicles throughout that time period, have used 24 volt systems for exactly the same reason higher voltages are being used today -- to reduce the amount of copper needed to carry high power levels.
As far as the safety issues go, I think the only way we're going to get anywhere without prohibitive expense and inconvenience is if we accept that the standard of comparison be "no more dangerous than a tank of gasoline" rather than "can't possibly be hazardous under any circumstances".
electric cars has certainly changed the electrical system of vehicles. the old 12v model has bigger range and Im looking forward to see low cost alternators and batteries and I believe it wouldn't be impossible.
Where is all this power going? For example, there was mention of a device rated 900v/500a continously, nearly half a megawatt, roughly 600HP! Really? This flies in the face of efficiency, the usual reason for being of electric vehicles.
I'd have imagined the higher voltage is employed to reduce amps, copper, and weight, but there's little mention of that here, in fact the emphasis is on high voltage and amperage.
I'd love to see cars go to a 24v primary battery, cutting existing amperages and wire sizing in half. This is considered an inherently safe voltage to handle with your bare hands. (Not that you should.)
Finally, even these higher voltages have been used for a century or more routinely in industry, I'd expect protection schemes there will crossover, with modifications for compactness and lightness. I've been working with them my entire adult life, and I'm close to retirement.
Tesla Motors plans to roll out a “compelling, affordable electric car” that will sell for about half the price of its high-profile Model S by the end of 2016, company chairman Elon Musk said last week.
From Dell / Intel® New Paradigms in Design Work Scott Hamilton, vertical market strategist for Dell Precision workstations, 5/2/2013 5
Early in my career, I worked as a draftsman and remember the days of drawing on vellum with numbered pencils and Mylar with plastic lead. This was a fun experience in the sense that I ...
I've been using workstations for more than 10 years and love finding ways to get more performance from my system. With demanding professional applications that require more power each ...
A lasting memory from my first job as an engineer in an auto assembly plant is standing on hard concrete at six in the morning, vending-machine coffee clutched in hand, listening to ...
For industrial control applications, or even a simple assembly line, that machine can go almost 24/7 without a break. But what happens when the task is a little more complex? That’s where the “smart” machine would come in. The smart machine is one that has some simple (or complex in some cases) processing capability to be able to adapt to changing conditions. Such machines are suited for a host of applications, including automotive, aerospace, defense, medical, computers and electronics, telecommunications, consumer goods, and so on. This radio show will show what’s possible with smart machines, and what tradeoffs need to be made to implement such a solution.
To save this item to your list of favorite Design News content so you can find it later in your Profile page, click the "Save It" button next to the item.
If you found this interesting or useful, please use the links to the services below to share it with other readers. You will need a free account with each service to share an item via that service.
Tweet This
40 
