When 12 volts Isn’t Enough

In the early part of the 1900s, virtually all cars and trucks had 6 Volt electrical systems. In other words, the battery was a 6 Volt battery, the starter was a 6 Volt starter, and all the accessories operated on 6 Volts. Back then, a 6 volt system was perfectly capable of powering everything in the cars and trucks of the day.

But things changed in the 1950s. Things like power windows, power seats, power antennas, radios, air conditioning and other accessories started to appear. And, unfortunately, this caused a problem for engineers who needed an electrical system that could power all these accessories.

The “more power” solution came from General Motors who in 1954 offered the first 12 Volt system in their Cadillac Series 62 models.  The rest of the American car industry quickly followed suit and within a few years every passenger car and truck made in the US had a 12 Volt electrical system.  The results for the consumer were significant. Lynch Chevrolet of Mukwonago, a local Chevrolet dealer in Mukwonago, WI, tells us that vehicles with 12 Volt systems were simply better. The started faster and multiple accessories, like the radio and AC could be used at the same time.

Today, though, we are at another point where we need more power. Today’s cars offer a buffet of new electronic technology and the car engines themselves, which traditionally used little electrical power, now have lots of electrically powered components (power steering, power cams, power water pumps, etc).

So, wouldn’t a simple solution be to just beef up the existing 12 Volt system? Maybe with larger alternators and more batteries?  Let’s do a little math and see how it all adds up. Take all the power consumed by all the electrical accessories in a new car -the power windows, the defroster, the heated seats, etc. – and the total will probably be between some 1.5 and 2.0 kilowatts of power needed. To supply 2.0 kilowatts of power, a standard alternator must be capable of churning out more than 140 amps. Not a problem, especially with the new water-cooled designs. But size up an alternator to feed the 3.0 kilowatts of power expected in cars built later this decade, and you’re looking at 200 amps.  This is an entirely different matter because that requires a really big alternator and heavy wiring to allow all those amps to flow around.

So, as any electrical technician will tell you, to drop the cable and alternator size issues, one simply needs to increase the voltage of the system. More volts means less amps are needed.  The number being thrown around currently is 42 Volts.  It has been calculated that 48 Volt systems would be just about right to power the complex demands of future automobiles.

Several car companies are already building cars with 48 Volt systems. The Bentley Bentayga has a 48 Volt system to drive an electrically-driven sway bar system, and Audi is using a 48 Volt system to power the industry’s first electric supercharger. We should be seeing many more cars going to 48 Volt systems too.

As more and more accessories and engine components become electrically powered, we should see a boost in system voltages. It will probably be another year or so and we should be seeing 48 Volts systems on American cars.

Share this post