Mechanical Engineer III - Battery Systems

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.

Mechanical Engineer III – Battery Systems

Engineering  |  Carlsbad, CA

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 are seeking a mechanical engineer with hands-on battery pack experience to contribute to the design, testing, and validation of battery modules and packs. This role is well-suited for an engineer who has worked on battery systems through the prototype and early production phases and is looking to grow their depth in thermal management, certification compliance, and systems integration.

Thermal analysis experience is a strong plus — we work on demanding discharge profiles and actively developing TIM selection processes, SimScale simulation workflows, and in-house thermal test campaigns.

What You'll Do

Battery Mechanical Design

•        Support mechanical design of battery modules and packs, including:

◦        Cell integration (prismatic, cylindrical, or pouch formats)

◦        Structural stack-ups and compression/retention systems

◦        Industrial and rack-mounted enclosure design

◦        Busbar and high-current interconnect geometry

•        Assist in defining mechanical strategies for shock, vibration, and environmental durability

•        Contribute to thermal management solutions, including passive heat plates, TIM selection, airflow layout, and fan integration

Thermal Analysis (Preferred Strength)

•        Run and interpret thermal simulations (SimScale, ANSYS, or equivalent CFD/FEA tools)

•        Support TIM and interface material evaluation — compare materials across thermal resistance, adhesion, and manufacturability criteria

•        Analyze thermal test data from discharge campaigns (2C, high-watt scenarios) and identify hotspot patterns

•        Correlate simulation results to physical test data and iterate on design accordingly

Certification Support

•        Support mechanical preparation for:

◦        UN 38.3 transport testing

◦        UL 1973 battery system certification

◦        UL 9540 / 9540A (as applicable)

•        Translate certification requirements into design constraints — creepage/clearance, enclosure integrity, protection strategies

•        Assist in documentation and test preparation for third-party lab submissions

Validation & Testing

•        Contribute to mechanical validation plans covering vibration, drop, thermal cycling, and abuse scenarios

•        Support root cause analysis during environmental and safety testing

•        Apply test findings to iterate on design robustness

Production & Manufacturing

•        Apply DFM principles during early design — tolerance stack-ups, assembly sequence, fixture considerations

•        Collaborate with cross-functional teams during prototype builds and controlled production releases

Required Qualifications

•        Bachelor's degree in Mechanical Engineering or related discipline

•        3–5 years of experience in a mechanical engineering role, with meaningful exposure to battery pack or energy storage product development

•        Experience with CAD tools (Onshape, SolidWorks, or equivalent)

•        Working knowledge of:

◦        Structural and mechanical design principles (stack-ups, tolerances, enclosures)

◦        Thermal management fundamentals in high-density electronics or battery systems

◦        Basic FEA or simulation concepts (structural or thermal)

•        Familiarity with battery safety and compliance frameworks (UN 38.3, UL 1973, or similar)

•        Ability to interpret and act on test data — you close the loop between simulation and hardware

Preferred Qualifications

•        Hands-on thermal simulation experience (SimScale, ANSYS Icepak, Fluent, or equivalent)

•        Experience characterizing or selecting TIM materials (thermal resistance, bond line, adhesion)

•        Exposure to UN 38.3 or UL 1973 test preparation or documentation

•        Experience with sodium-ion, lithium-ion, or LTO cell formats in pack-level applications

•        Familiarity with IEC 62619 or other international battery standards

•        Experience supporting DFM discussions with contract manufacturers

Compensation & Benefits

•        Salary range: $130,000 – $175,000 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 grow into a senior technical role on a platform that is shaping next-generation energy storage

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

The pay range for this role is:

110,000.00 – 140,000.00 USD per year (Ca