The rise of 48V electrical systems

48V ELECTRICS

BY JESSE CROSSE & MOTOR STAFF

It may not sound like it, but 48-volt technology is one of the smartest innovations coming to the world of cars

ITíS RELATIVELY cheap and fits into existing vehicle architectures, but is only just coming of age. As well as providing a hybrid drive, the 48-volt electrical systems emerging around the world can handle loads of tasks that need doing around the car but previously used energy created by burning fuel.


While 48 might look like a figure plucked out of the air after a brainstorming session in the bar, there are good reasons for it. The first is that itís classified as low voltage and safe. Anything above 60 volts in a car is deemed a high-voltage system - and a high-voltage system is a lot more expensive than a low-voltage one. The safety systems, power controllers and heavy cabling involved in a high-voltage system all contribute to the high price, whether itís 65V or 800V.

THE USE OF 48-VOLT ARCHITECTURES IS ON THE RISE BECAUSE THE ELECTRICAL CONSUMPTION OF CARS HAS GONE UP

Power (watts) derives from the voltage and the current (amperage). Increase either and the wattage goes up. But increasing amperage requires the use of larger, heavier, more expensive cables to reduce electrical resistance, whereas using a higher voltage and lower current doesnít.

A 48V battery is small and relatively inexpensive, and installation is straightforward because a 48V electrical architecture sits alongside the carís original 12V system.

The use of 48V architectures is on the rise because the electrical consumption of cars has gone up due to more complex infotainment, connectivity and navigation systems and the dozens of driver assistance systems emerging. Cameras, radar, sensors and controllers plus the electronic systems to go with them all need more power than a 12V system can deliver.

A 48V set-up also allows jobs normally done by the engine - such as powering electric water pumps, air conditioning compressors, oil pumps and heating - to be offloaded to electrical power, saving fuel. Automatic gearboxes can function when engines are shut down thanks to electric oil pumps; auto stop-start becomes smoother and can kick in before the car comes to a halt, saving more fuel; and electric boosters in diesels reduce turbo lag.

There are limitations, though. Until now, the assumed maximum power of a low-voltage hybrid (or EV) motor/generator has been around 12kW. That low power figure has limited mild hybrids to boosting power and recovering energy, rather than providing an electric-only mode like a (high-power) full hybrid.

Now, though, it looks as though that limit has been busted. Component supplier Continental recently announced a new 48V mild-hybrid drivetrain producing 30kW. The improvement has been achieved by increasing the efficiency of the power control system and designing a high-efficiency, water-cooled motor/generator. The increase in power means itís possible to drive short distances in electric-only mode like a full hybrid and makes the prospect of powering small city cars and scooters using 48V systems even more realistic.