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48 volt: what it is and why it’s important

14th March 2019

Electric vehicle manufacturers are starting to adopt 48-volt electrical systems. The latest specialist EVs will be using components that more power, additional torque, and – with automation and smart engineering – greater intelligence. The potential applications of 48V are exciting, representing a huge innovation in automotive design.

With more technical capability, comes a greater need for power. For specialist vehicles, this need for power only grows. Like passenger vehicles, specialist EVs can reap the benefits of this higher voltage system without the size and/or weight trade-offs. The solution for many is adopting higher-voltage 48V from typical 12V systems. Thanks to advancements in engineering: it has no lighting or surge-requirements and the range is more limited to 30 – 60V.

What is 48 volt and how does it benefit specialist vehicles?

Typical 24 volt systems have been popular in Europe for some time. In the early 2000s, proposals for 42-volt systems fizzled out because of cost concerns and practicality. Compared with 24V, only half as much current is required to get the same power. Today, the industry seems better prepared, thanks to a better understanding of their capabilities.

48V’s limited range of 30-60V has led to its re-emergence. The reason this range is effective, regardless of capping voltages below a 60V cut-off, is because they meet Safety-Extra Low-Voltage (SELV) requirements. 48V can distribute power to your commercial EV components, minimising copper losses without causing unsafe SELV issues. The output can reach 57.6V before the power supply shuts down, and protects your downstream circuitry from damage.

Increase of Cost-Effective Power

In cost-terms, anything higher than 60-volts not only breaches SELV, but becomes more expensive to implement. Designers would need special cabling and wiring – not to mention tighter regulation (you can read about regulations here). 48V systems hit the sweet-spot – providing more efficient power distribution throughout, optimising engine accessories and other electronics on the vehicle. Higher-voltage designs also allow for improved power generation.

The system’s battery is also more efficient. With an integer multiple of the current 12V systems (seen in the commercial vehicle industry) 48V allows for four dependable lead-acid batteries placed in series. Thus eliminating the need for expensive batteries. 48V systems have the benefit of increasing power to components without raising the current – minimising copper, which requires expensive cabling and a loss in transmission.

48V is competent enough in handling EV components without compromising fuel-economising strategies.

Packaging made Easy

Applying 48V in your designs could give you more flexibility in packaging, too. When compared to belt-driven alternatives like the front-end accessory drive (FEAD), components can be packaged at the front of a truck’s engine.

Carl R. Smith, Commercial Manager, Engineering and Customer Support, for Eaton eMobility believes, ‘48V will begin an initial adoption in the commercial truck and agricultural equipment markets within less than five years’. John Deere, for example, already has adopted 48V – introducing it in one of their row-crop planters. This increases speed and eliminates hydraulic lines – another triumph of packaging potential for specialist designers.

How 48V can Enhance Hybrids

For mild hybrids, 48V is being used for energy recuperation. Companies are designing boost recuperation machines (BRM) to work with additional electric compressors – minimising the choice between driving dynamically and efficiently. Features include brake energy recovery, electrical torque support, load point optimization and smoother start/stop engine starts. With braking, for example, part of the kinetic energy is recovered and stored in the 48V battery – recharging battery cells.

48V also contributes to electrical torque support – to a downsized combustion engine – during boosting operations. Specialist vehicles (particularly trucks) rely on higher torque with less energy wastage. Along with an optimised start/stop system, this is achievable thanks to 48V’s smaller voltage, delivering four times more power than traditional hybrid systems.

Intelligent technology within BRM is being used to regulate tailgating by predictive coasting systems. This makes driving a commercial vehicle much safer. It is expected that as of 2020, four million vehicles will be adopting BRM technology.

MHEVs (mild hybrids work by only using 48V-driven components like electric fans, electric water pump, a vein-type air compressor, electric power steering and a 15-kW crank assist generator. When tried on trucks as part of a typical drive cycle, the system demonstrated 28% fuel savings, a NOx reduction of 46%, and a particulate reduction of 93%.

Half the benefit comes from auxiliary systems, improving the thermal performance of the engine – along with more precise control. This is enhanced by a boost in the back of the engine (in crank assist mode) – particularly useful when the engine needs some extra acceleration.

MHEV is one way 48V can be applied to your hybrid design, with a number of supporting components available from Dalroad.

Proving a Point with TCO

If there is no total-cost-of-ownership benefit, fleet owners are less likely to electrify their vehicles. With impending regulation on fossil fuels, MHEV is one such way that manufacturers are proving the success of 48V for fleets; as a system capable of running EV components, without higher costs (thanks to aforementioned control in currents).

Keep in mind the benefits are different depending on the duty-cycle. For on-the-road Class 8 trucks, benefits are primarily in controlling the air compressor, steering pump, and other auxiliaries, turning them off when not in use.

Alternatively, if you are designing for a Class 6 delivery truck, with many transients, and starts and stops, the 48V system would be used for cooling systems, keeping engine temperatures low.

48V Hybridization as Innovation

Because of this variety of duty cycles, 48V mild hybrids can spark innovative applications to a specialist vehicle design.

The market will electrify. In some applications, 48V mild hybrids will become standard where there are problems justifying a fully battery-electric vehicle solution.

This could also work for the intermediary freight market, delivering goods on the fringes of cities. While many cities are banning ICEs (internal combustion engines) altogether, ICE-powered trucks will still supply the fringes, and mild, 48V hybridization could be a solution. Fleets without the means to fully-electrify could find this a satisfying alternative for now.

Time to go 48V?

Battery costs are rapidly reducing – signalling wider EV adoption. 48V uses smaller batteries, yet competently caters to increased e-power requirements for connectivity and autonomy. The good part: they cost less than high voltage systems. This is once again, the 48V sweet spot.

If battery prices drop low enough, however, designers might opt for fully electrifying.

For now, the 48V architectures provide the optimal trade-off of meeting regulations, performance, weight and cost.

The team at Dalroad is on-hand to assist you with designing your commercial vehicle. If you are working with 12V architecture, we can help reveal how you can overhaul the design to work with an upgraded 48V system.

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