12V versus 24V versus 36V Vehicle Systems

Who Remembers 6-volt Car Batteries?

best alternator testing methodMost cars manufactured in North America before 1950 used 6-volt batteries. This voltage was adequate given the low power requirements of vehicles at that time. During and after the World War II, however, copper prices rose and cars added more control circuits, motors and electronic devices. By the mid-1950s, 12-volt automotive electrical systems were the norm for new cars.

Higher voltages saved money and were more reliable. Ohm’s Law dictates that for an equal amount of power in a circuit, a doubling of the voltage halves the amount of current required. Simply put, higher current requires larger wires.

Thus, the change to 12 volts meant less copper was needed to transfer power throughout a vehicle. Additionally, advances in battery technology created 12-volt batteries the same size as 6-volt batteries.

Higher Voltage Systems Have Additional Advantages:

  • Motors and other electrical components were made with less copper.
  • Electrical relays and motor brushes lasted longer.
  • Voltage drops due to bad connections are reduced.
  • There is less stress on lead-acid batteries during engine starts.
  • Higher torque starters could be made to handle higher compression engines.

Bulb filaments had to be thicker to create the same amount of light, but since modern cars use few, if any, filament bulbs that issue is moot.

24-Volt Vehicle Systems

ALTERNATOR REPLACEMENT24-volt systems have similar advantages over 12-volt systems. Smaller, lighter wiring harnesses can be utilized, electric motors of the same size are more powerful and the effects of voltage drops are minimized.

These higher voltage electrical systems are common in commercial, industrial and military vehicles for these reasons. These vehicles typically use diesel engines with high compression, so powerful starters are required. Reliability is increased due to fewer problems with voltage drops.

Consumer level cars and trucks, even ones with diesel engines, do not use 24-volt systems mainly because inexpensive batteries come in 12-volt sizes, so two would be required. Furthermore, most components and accessories for retail vehicles are designed for a 12-volt power supply.

36-Volt Vehicles and Equipment

36 and higher voltage systems are not uncommon in commercial and industrial equipment. Such high voltages are required for vehicles that use electric motors for propulsion in lieu of internal combustion engines because electrical current demands are so high that cable sizes would be ridiculously large.

Included in this class of equipment are fork lifts, tow tractors and personnel transporters. Golf carts and electric cars also utilize high voltage systems. Typically, several deep-cycle batteries instead of lead-acid types are employed and recharged daily.

Impact of Higher Voltage Systems on Alternator Performance

The de facto standard for alternator design is the Lundell alternator. It is not the most efficient design but is easy to build. If, say, a standard 14V Lundell alternator is utilized in a higher voltage system, however, its power versus voltage curve becomes impractical at higher RPMs.

A Lundell alternator can be rewound to operate correctly at higher voltages by increasing the number of stator windings while reducing the wire size, but less expensive methods that utilize additional electronic circuitry overcome this limitation more cost-effectively. Electronically, it is even possible to create dual voltage alternators.

Where to from Here?

We probably have reached a plateau in voltage for cars and other vehicles. Higher voltage systems for personal vehicles have been proposed, but even as cars sport more electronic features, the power consumption of individual devices drops. So, do not expect to see higher voltage car batteries soon.

If you need an alternator for your fork lift, tow tractor, personnel transporter or any other industrial vehicle, contact us today.