May 15, 2001
by Jim Kerr
Right now, our cars and trucks operate mainly on a 12 volt electrical system. There are a few exceptions, such as heated windshields, high intensity discharge headlamps, and a few models with luminescent exterior marker lights, which operate at 80 volts or more. In the very near future, new cars will be switching over to 42-volt electrical systems. Forty-two volt systems will begin to appear within the next 2 to 3 years and this voltage has been chosen as the industry standard for several reasons.
The first and primary reason for switching to 42 volt electrical systems is reliability. Older readers or admirers of antique automobiles will remember the old 6-volt electrical systems that were common until the late 1950′s. At that time, the auto manufacturers switched to 12-volt systems for better reliability with the increase in electrical equipment on the vehicles. Now, another large increase in electrical content and computers on automobiles is creating the push to 42 volts.
History is repeating itself, and a look at the past will show how 42 volts will improve the future. Six volt systems worked well, but one of the basic laws of electricity is that the higher the voltage, the more current will flow down a wire. Current or amperes, as it is called in electrical terms, is the flow of electricity that actually does the work. Switching to 12 volts enabled the manufacturers to push more current down the same wires so more powerful electrical devices could be operated. Another benefit was that wire size could be reduced on circuits that did not require high current flows.
Multiple computers, mind-blowing sound systems, and luxuries such as heated seats, heated steering wheels, heads-up displays, and navigation systems all place a high load on the car’s electrical system. Forty-two volt systems will be able to deliver the necessary current to operate these systems without installing power wires the size of your arm to handle it. Keeping wiring harnesses small and light weight are a definite advantage in manufacturing and in long term fuel economy.
Another not so obvious advantage to 42-volt systems is their ability to overcome resistance in wire connections. Computer sensor circuits on our automobiles typically operate at close to five volts. The current flow through these sensor circuits is measured in milli-amps or one/thousandths of an amp. Any resistance in an electrical connector will cause a change in current flow and the computer receives a wrong input. The results can be incorrect system operation, intermittent faults, or no operation at all!
It is difficult to find problems caused by excessive resistance. The resistance at a connector can be so small that it is not visible with the human eye, and can only be measured with quality meters when electricity is flowing through the circuit. Yet, this is enough to affect computer operation. Sometimes, just unplugging and reconnecting a connector is enough to correct a problem. With 42 volts, there is enough electrical push to overcome these small resistances and the computers will receive the correct input signals.
The first 42-volt systems will likely be a hybrid. Some of the vehicle will work on 12 volts while the computer systems work on 42 volts. The 42-volt system is actually based on a 36-volt battery, but it is called 42 volts because this is what it will operate at when the vehicle is running. This is much like today’s systems, which operate at 14 volts but use a 12-volt battery.
Modules will convert the 42 volts of the charging system into 14 volts so the older technology components will be able to function. These modules may be centrally located, powering several 12-volt devices, but advances in electronics may allow each 12-volt appliance to have its own module. Regardless of the configuration, hybrid systems will be present for a few years.
Eventually, with new automobile designs, the systems will be converted completely to 42 volts systems and the complexity of diagnosing dual voltage systems will disappear. In the meantime, there is sure to be lots of confusion in the buying public because of the changes in electrical systems. Electricity flows invisibly, and few technicians, let alone drivers, really understand how it works and how to diagnose problems. Those technicians who do understand electricity are worth their weight in gold and should be cherished highly. They repair cars faster, correctly, and more economically.
Forty-two volt systems are the future. They will help decrease electrical problems in the future and make our cars easier to diagnose and repair.