Overview
In a video conversation between Munro and Tesla technicians, Tesla showed a Gen4 zonal controller incorporating a 48V system. Based on the available information, Tesla appears to place DC/DC conversion modules on major controllers to allow conversion between 12V and 48V, with most subsystems moving toward 48V e-fuse protection.
Part 1: Distribution design changes
Mechanical and connector changes
In the previous 12V designs, connectors use press-fit pins on the PCB, and connector modules are integrated into the top housing. In the 48V revision, connectors are optimized to support wiring-harness bridging, and the use of 48V e-fuses reduces the overall volume of the power distribution unit.
Electrical and circuit-level changes
From a circuit-design perspective, an MCU manages power distribution and other body-control functions. The 12V design used 34 low RDS(on) MOSFETs for power distribution along with about 20 high-side drivers for switching. In the 48V design, Tesla implements a dedicated bidirectional converter between 48V and 16V (Tesla describes the intermediate voltage as 16V). The architecture retains some 12V rails for smaller loads that are not migrated to 48V.
Transitioning from 12V to 48V requires changes to protection devices at the power layer, deployment of 48V e-fuses, and corresponding high-side switches. A power module capable of providing both 48V and 12V (with an intermediate 16V rail referenced by Tesla) is needed to supply specific loads and sensors.
Part 2: Industry adoption considerations
Ford CEO Jim Farley wrote that he received Tesla's technical document "How to design a 48V low-voltage architecture for a vehicle," which describes the Cybertruck's 48V low-voltage bus architecture and is presented in a manner similar to Tesla's NACS charging specification.
Compared with adopting NACS, other automakers face several challenges when migrating to a 48V low-voltage architecture:
- Many ECUs must be redesigned, starting with zonal controllers.
- A large number of loads need to be migrated to 48V. While the load conversion itself is manageable, protection devices and switching elements must be redesigned accordingly.
The migration is driven largely by the increased current demands from advanced driver-assistance and other high-power features that stress the traditional 12V bus. The transition process is expected to be gradual.
Summary
Introducing 48V systems in vehicles is not new, but converting the vehicle distribution architecture and redesigning all controllers for 48V operation is a significant engineering challenge. Companies in China and abroad are likely to approach such migrations cautiously.
