Watashi, the issue with 300V, is that requires a 300V battery solution and everything to be 300V that is connected (i.e. AC compressor, etc.). 300V charging and control, safety systems, etc. are all more expensive than 48V. The goal here is mass adoption.
In reliability engineering we have a term: root cause. As in, Europeans are coerced into stop start by higher taxes. Europeans pay more for fuel than us in North America due to taxes and import duties. And this was not brought about by noble environmental concerns. It is well known, they paid much more than us before the environment was a convenient excuse. Before global cooling transformed to global warming transformed to climate change, remember the European 60's muscle cars? Me neither.
We need cheap energy and now our government is in the way. Nuclear power and now coal is being regulated out of existence. There is a reason the Saudi's are scared to death of oil shale and fracking. We could easily have $2 a gallon gasoline in North America if BIG OIL was allowed to exploit our resources. This is not about the environment either. The environmental movement is just a means to an ends. Every new energy technology that shows promise gets beaten with that stick. Cheap energy would bring us out of this economic quagmire faster than a bullet train and reduce the real unemployment rate below 12%. It could save our economy in spite of the socialist utopians.
Start-Stop and Regenerative Braking are Hybrid terms. This assumes a hybrid or 'hybrid lite' drivetrain. But 48V is a very poor choice for providing drivetrain power. If you are going to have a hybrid, just use the 300+ Volts. If you are not going to have a hybrid, don't add a bunch of parts (weight/cost) just to support a secondary voltage architecture.
I was very much onboard with the 42V or 48V back 10 or so years ago. The advantages in terms of weight (smaller conductors) and beltless accessories are substantial. The 'three batteries' was a short term solution, but an adequate, single battery could have been available by the time a production car rolled out.
The largest obstacle I recall was the prevalence of 12V parts. The fact that a car manufacturer along with all the electronics providers would have to start from scratch is a major risk for a company to undertake. Staying with 12V is much easier than dealing with things like unknown component reliability and a non-existent supply chain.
I have been working on these dual voltage network for years some roadblocks have gone away today
- downsizing of motors is a reality today a 1.6l engine delivers 120HP (in Europe !!) - if we want to go further in downsizing the lack of power at low throttle will be such that electric compensation becomes necessary w/o going to full hybrid that is the most economical way to improve FE - the 48V will be devoted to high power electric consumers only, before dual network was eveywhere raising FMEA pb that were non solvable - Li-ion battery is for sure now a reality and such a battery can easily fit in the rear trunk w/o any risk at least not bigger that the big pack of hybrid that's behing the backrow seats !! - our conclusion was that FE could be boosted by 25% combined with downsizing at this time the market was not ready to pay for this technology
If the Li battery has higher power density, what's the point of the heavy lead acid battery, and associated heavy wiring and components? And couldn't even that lead acid battery be available in a 48v version too?
Is the concern an ability to 'jump start' the cars? I ran both my Prius batteries down once (a shameful story I won't go into) and it wouldn't jump start anyhow- the computer memory was gone.
If 48V is what is needed to allow putting regerative braking in autos, then this could catch on quickly with drivers that spend most of their time in the city.
The dual voltage idea is clever. All the 12V lighting and other functions that currently exists don't need to be redisigned and people can appreciate that they are still interfacing with only 12V components.
Any time I see projected numbers like the efficiency numbers mentioned here, I immediately take the number down to 1/3 the projected number. I've found that to be far more accurate when it comes to real-world results. At times I've seen it be up to half the initial projected numbers, but that's about it.
If the people who are advocating new technologies would put out real-world expected gains instead of "up to" pie-in-the-sky numbers, their credibility for future projects would be helped. "Up to" numbers assume that everything is ideal, works perfectly, etc., and they usually just are not valid.
For this project, if they're stating that fuel economy will go up by "possibly as much as 15 percent", then I would place a very large bet that the actual increase will be about five percent once the system is rolled out and all the real-world constraints come into play.
I would be far less skeptical of improvement claims if the projected improvement numbers weren't usually overinflated to get people to buy into the concept.
I recall the earlier articles saying that 42v was the upper limit of safe voltage in the vehicle for the end user. Now, 48v is okay?
I'm more concerned about a lithium ion battery in my engine compartment. It's one of the worst environments for a battery with the heat from the engine, and being exposed to the elements. After reading about the issues with lithium ion batteries catching fire, one place that I do not want a big one, is in my car, where I have plenty of gasoline and other combustible matter!
I hope that traditional compressor based air conditioning will someday be replaced by new technology. Wasn't there some "sonic" air conditioner invented a while ago? A peltier junction based system (or similar technology) with no refrigerant and associated piping would be a wonderful thing.
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