The Accumulator is the lifeblood of our EV; housing the battery pack, tractive system wiring, and associated control electronics. Its purpose in the car is to safely store and deliver power from the lithium-ion cells to the tractive system, providing the voltage and current needed to drive the electric motors. Its design balances performance goals with strict SAE requirements on safety, structural integrity, and electrical integration.
The accumulator design begins with the enclosure, modeled in SolidWorks using 16-gauge and 18-gauge steel to evaluate weight reduction strategies. Two main layouts are explored: a rectangular enclosure with removable connector panels, and a U-shaped chassis integration. Panel and frame thicknesses are tuned to meet Formula SAE requirements.
The battery pack architecture uses a 24s4p layout per segment built from Sony/Murata VTC5A cells chosen for their high discharge current capability. Each segment operates between 60–100.8 V and is capped at 120 V per SAE rules, with the full accumulator supporting an 800 V maximum architecture. Six segments deliver 84.7 kW peak power, while eight segments provide up to 112.9 kW, with each storing 3.8 MJ of energy at 10.4 Ah. Lightweight aluminum bus bars replace copper to reduce mass while keeping temperature rise below 10 °C at 140 A peak current.
The electronics system integrates three custom PCBs: the Base PCB for isoSPI and CAN communication, the BMS slave boards monitoring 24 cells each, and the Precharge/Discharge PCB redesigned with a single SPDT relay rated to 900 V. Together these boards handle cell monitoring, tractive system isolation, and safe startup/shutdown of the accumulator.
The final accumulator achieves a voltage range up to 800 V, delivering up to 112.9 kW peak power while cutting system weight from 98 kg in the 2023 design to 52 kg; a 47% reduction.
Each battery segment stores 3.8 MJ of energy at 10.4 Ah, and lightweight aluminum bus bars limit temperature rise to under 10 °C at 140 A peak current.
The integrated PCBs ensure reliable monitoring, isolation, and pre-charge/discharge functions, bringing the system into compliance with Formula SAE rules while improving overall reliability and serviceability.
