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What happened to the 42V auto?

A few years ago, there was lots of serious talk of cars transitioning to 42V supplies, either in addition to, or to replace, the venerable 12V system they have used for decades. The reasons for going to a supply potential that was three times the present supply rail were clear: the increased power requirements of today's cars could not be met efficiently by a lower-voltage system; the wire diameters needed to keep IR losses down were too big, and thus costly while consuming precious space; connectors were having problems handling the current; and the entire alternator charging/battery storage subsystem was, so to speak, running out of gas.

Although some car vendors did install dual-supply dc systems in a few models, and key component vendors produced relays and other parts for 42V, the reality is that no one is talking about 42V systems breaking out any time soon—and many industry experts now say “it isn’t going to happen.”

So, how did conventional wisdom go wrong? After all, many of the predictions came not from the usual crew of quick-with-the-quote analysts, but from insiders who were very knowledgeable about the technology and markets.

As is often the case in these situations, there is no single reason for the 42V systems not taking off as anticipated. Among the aspects cited are technical, business, and aftermarket issues, including:

  • The immense and well-tuned 12V infrastructure
  • The familiarity, with 12V systems, of the service industry that keeps cars going
  • The industry's decision to instead invest in developing components for hybrid and alternative vehicles squeezed out investment in 42V R&D; plus the desire to not make too many major automotive changes in the same time window
  • The technical dilemma of designing-in a single 42V bus system versus dual 12/42V bus system
  • Problems with long-reliability: at 12V DC loads, a relay's contacts don't arc or corrode; at 42V DC, the relay contacts can arc and pit as they open (unlike AC relays which self-extinguish when their contacts open)
  • Sizing, keying, and standards for 42V connectors—not elegant, but critical practical factors
  • Safety issues in the field, during test and repair, with 42V systems

There are lessons in the turnaround of the enthusiasm for 42V systems. A well-established infrastructure is hard to revise, there are only so many new initiatives component suppliers and OEMs can embrace at one time, and nasty technical and field issues can derail what, in theory, makes good sense.

In contrast, a product that is radically different and does not try to fit in with the existing framework, such as the iPod, can really take off and own a new market in just a few years, if the market, technical, and serendipity factors line up just right. In our industry, which has little time or enthusiasm for looking back in that rear-view mirror as we hurtle forward, it's sometimes interesting to do so and ask “what happened?”

But here's my main question: the 12V system was supposed to soon be inadequate due to the increasing electrical load of the car. So, how is that potential calamity being averted? Or is the 12V problem not as bad as it was made out to be?

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