Mechanical Engineer III – Battery Systems Engineering in Carlsbad, California at Proper Voltage

Please note that we are unable to provide visa sponsorship for this position.

About Proper Voltage

Proper Voltage is unlocking the next generation of battery technology across robotics, data centers, and defense.

We're building intelligent battery systems that make advanced chemistries (sodium-ion, lithium-titanate, lithium-silicon) work in products that were never designed for them. Humanoid robots can upgrade power systems without redesigning their entire platform. Data centers get safer, cheaper backup power. Drones and autonomous vehicles get higher energy density without lengthy integration cycles.

If you want to work on hard engineering problems that matter this is the place.

Job Overview

We're looking for an experienced mechanical engineer to take ownership of battery pack and module design from concept through production. This is a senior individual-contributor role: you'll drive design decisions independently, lead thermal and structural analysis efforts, and mentor junior engineers, while working closely with electrical, controls, and manufacturing teams to ship real hardware.

Deep experience with thermal analysis and simulation is strongly preferred. We run active thermal test campaigns and simulation workflows, and this role owns that work rather than just supporting it.

What you'll do

Battery Mechanical Design

• Own mechanical design of battery modules and packs end-to-end, including:
• Cell integration concepts (prismatic, cylindrical, or pouch formats)
• Structural components, brackets, and enclosure design
• Busbar and interconnect geometry
• Drive design reviews, tolerance stack-up analysis, and DFM decisions
• Define mechanical interfaces across the assembly and negotiate trade-offs with electrical and controls teams
• Make final calls on design trade-offs balancing performance, cost, and manufacturability

Thermal Analysis

• Own thermal simulation setup, execution, and post-processing (SimScale, ANSYS, or equivalent)
• Evaluate and select TIM and interface materials based on performance and cost trade-offs
• Design and run thermal test campaigns; independently analyze discharge data and identify root causes of thermal issues
• Correlate simulation outputs to physical test results and refine models accordingly

Testing & Validation

• Define and lead mechanical validation test plans, vibration, drop, thermal cycling
• Own root cause analysis on test findings and drive corrective actions to closure
• Review and approve test reports and documentation from junior engineers

Documentation, Process & Mentorship

• Maintain CAD revision history and BOM structure for your subsystems
• Author engineering documentation, test procedures, and work instructions
• Lead design review discussions and drive action items to closure
• Mentor Mechanical Engineer I/II staff on CAD practices, GD&T, and design fundamentals

Required Qualifications

• Bachelor's degree in Mechanical Engineering or closely related discipline
• 5+ years of professional mechanical engineering experience, ideally in battery, EV, or energy storage hardware
• Demonstrated track record taking designs from concept through production
• Expert-level 3D CAD skills (Onshape, SolidWorks, or equivalent)
• Strong command of GD&T, tolerance stack-up analysis, and DFM principles
• Experience owning mechanical subsystems independently, with minimal oversight
• Ability to mentor junior engineers and lead design review discussions

Preferred Qualifications

• Proficiency with FEA or CFD tools (SimScale, ANSYS, SolidWorks Simulation) for thermal and structural analysis
• Direct experience with battery-powered devices, EV systems, or energy storage products
• Hands-on experience with manufacturing processes — machining, sheet metal, plastics, assembly
• Working knowledge of UN 38.3 or UL safety standards
• Experience leading a physical prototype build from CAD through assembled hardware
• Prior experience mentoring or informally leading other engineers

Compensation & Benefits

• Salary range: $130,000 – $165,000 annually (commensurate with experience)
• Equity participation as part of total compensation
• Comprehensive healthcare benefits (medical, dental, vision)
• Paid time off and company holidays
• Opportunity to shape battery mechanical engineering practices as the team scales

Ready to work on power systems that matter? Let's talk.