The automotive industry has been clinging to 12-volt electrical systems since the Fifties, and even with the advent of hybrids and EVs featuring high-voltage traction batteries, a 12-volt battery continues to power essential components like window regulators, seat motors, and headlights. While a few 48-volt “mild-hybrid” vehicles have emerged, Tesla has boldly taken the lead by adopting a 48-volt system for its pure EV, the Cybertruck, marking a significant departure that its marketing team wants you to take notice of.
Elon Musk, in an interview, emphasized the challenges posed by the industry’s deep-rooted reliance on 12-volt systems, stating, “The entire supply chain, the entire design infrastructure is designed for 12 volts. This is why it’s been stuck at this absurdly low number for a long time.” Musk’s commitment to this shift led Tesla to send a manual on building a 48-volt car to the CEOs of major automakers, a move confirmed by Ford’s CEO Jim Farley on Twitter.
This move by Tesla appears to be another instance of the company breaking new ground, compelling traditional automakers to catch up – reminiscent of their achievements with over-the-air software updates and Gigacasting. While the Cybertruck’s shift to 48-volt electrics is presented as another groundbreaking move by Tesla, as always, there’s a need to sift through the hyperbolic messaging to uncover the genuine advancements made.
Firstly, the rationale behind increasing voltage lies in Ohm’s Law, which establishes that voltage (V) is equal to the product of current (I) and resistance (R) – V=IR. Assuming a fixed resistance, elevating voltage leads to a reduction in current. This decrease in current allows for the use of smaller wires to transmit the same power, resulting in weight savings, cost efficiency, and improved overall vehicle efficiency. Additionally, higher current is associated with increased energy loss as heat. Consequently, a 12-volt system not only proves inefficient at higher power levels but also necessitates components with larger heat sinks compared to higher-voltage systems.
The automotive industry transitioned from 6- to 12-volt electrics in the 1950s to meet the escalating power demands posed by more advanced electrical components, particularly ignition systems designed for higher-compression engines. Despite the significant growth in the number of electrical systems integrated into vehicles since then, the industry has predominantly adhered to the 12-volt electrical standard.
The auto industry worked to move to a higher voltage standard in the 1990s and early 2000s, anticipating the need for higher electric power in passenger cars. A 1999 SAE paper written by Ford engineers about a 36-volt system concluded that “[n]ew electrical functions features with power requirements of several hundred watts or more will require the availability of a high-voltage power supply in order to be practical in term efficiency, cost of wiring, packaging, and semiconductor controls.”
But a large switchover never happened.
“[Automakers] were able to find efficiencies elsewhere that eliminated the need to spend that extra money to go to a higher-voltage system,” said Sam Abuelsamid, principal research analyst with Guidehouse Insights.
Now, however, we do have some 48-volt cars on the market.
“As we got into the late 2000s,” Abuelsamid said, “we started adding so many features to cars. Heated seats, heated steering wheels, adaptive dampers, all these things that consume electrical power. Plus, wanting to electrify other electric components on the engine to reduce parasitic losses.”
The adoption of 48-volt systems by some automakers was driven by specific needs, such as integrated starter-generators or active anti-roll bars. However, it’s essential to note that these systems still rely on at least two DC-DC converters to power 12- and 5-volt electrical components. While 48 volts may facilitate the use of smaller wiring, there are practical limitations to how small the wires can be. Additionally, 48-volt systems require stronger connectors and shielding to minimize the risk of arcing. This voltage level also represents an upper limit for electrical systems that don’t necessitate more stringent safety standards.
In the case of the Cybertruck, details about specific 48-volt components are not entirely clear due to Tesla’s limited communication channels. However, it’s known that certain components, like the audio amplifiers, operate at 24 volts. The Cybertruck is designed with provisions to be jump-started by a 12-volt battery in the event of a 48-volt battery failure.
Examining the online parts catalog for the Cybertruck reveals that some components, such as window regulators, are explicitly designed for 48 volts. However, the part number for the radar-sensor assembly is similar to that of the Model Y, suggesting it could be a 12- or 5-volt component.
In essence, Tesla’s approach with the Cybertruck doesn’t seem drastically different from what other automakers have already implemented. Tesla claims to have reduced the weight of the wiring harness and the number of wires in the car, partly thanks to a new Etherloop data system.
The 48-volt system in the Cybertruck introduces a groundbreaking feature – steer-by-wire (SBW), marking the first instance of this technology in a production car without a traditional steering shaft. While other vehicles like the Infiniti Q50 offer SBW, they typically retain a traditional column as a backup. In the case of the Cybertruck, it’s speculated that Tesla is leveraging components from ZF, a supplier known for developing SBW systems for 48-volt vehicles. Videos featuring various Cybertruck components reveal the presence of a ZF logo on the steering rack, suggesting the use of ZF-designed components capable of working in both EVs and internal-combustion cars.
However, questions arise about the rationale for adopting a 48-volt system in an EV like the Cybertruck. Unlike internal-combustion cars, where the jump from 12 to 48 volts results in a substantial increase in available electricity (from around 2/2.5 to 10/12 kW), EVs typically operate at much higher voltages, with even low-end EVs having a minimum of 100 kW from the battery. As such, the advantages of moving to 48 volts in an EV become less apparent, leading to speculation about the true driving force behind Tesla’s decision.
While the introduction of SBW may be a compelling reason for Tesla’s adoption of a 48-volt system, the broader benefits in an EV context remain less clear. The Cybertruck’s use of this technology raises questions about whether Tesla’s approach is a revolutionary genius move or perhaps overly clever. The 48-volt system becomes emblematic of the broader Cybertruck narrative – is it a groundbreaking innovation or a case of being too clever for its own good?
