Senior Battery Mechanical Engineer

What we’re building The marine industry supports recreation, global commerce, and national defense. And yet it runs on technology that hasn't meaningfully changed in fifty years. Until now. Arc is on a mission to electrify the marine industry. We're rethinking powertrains, software, and vessel designs from first principles. And we're already executing. We started with consumers to develop and harden our core technology. We’re now scaling production of our flagship model with new models and sectors on the horizon. Now we’re extending our platform to commercial applications, starting with tugs, ferries, and defense, with years worth of signed contracts and a pipeline that spans every vessel type on the water. The technology is proven, the momentum is building, and the opportunity is enormous. The marine industry is going electric and Arc is building the platform that powers it Who we’re looking for As Arc’s Senior Battery Mechanical Engineer you will own the mechanical design of our battery packs. We're looking for someone fired up by the mission and ready to build. You'll thrive here if you move fast, take ownership, and care about the details. This is a full-time, on-site role at our Los Angeles headquarters. What You'll Do Leading battery pack mechanical design across Arc's product lines — defining pack architecture and carrying it through to detailed structure, enclosure, busbar, and electronics packaging design Performing structural analysis (FEA, hand calculations, and numerical modeling) on enclosures, busbars, and internal components against the vibration, shock, and slamming loads seen on the water Sizing and designing pack thermal management systems, including cold plates, coolant routing, and heat rejection, and validating models against test data Partnering closely with electrical engineering on cell selection, busbar and interconnect design, HV isolation and creepage/clearance, and BMS and sensor integration Packaging packs into tight hull envelopes, balancing energy density, mass, safety, serviceability, and manufacturability Building and testing prototypes hands-on, running thermal, structural, and abuse validation and driving design iterations from the results Supporting sea trials to validate and certify systems in the field Interfacing with cell, module and component suppliers and supporting production ramp Minimum Qualifications 6+ years of mechanical engineering experience, including 3+ years designing battery packs or modules and owning them from concept through production Excellent grasp of structural and thermal engineering fundamentals, with hands-on experience applying FEA, hand calculations, and numerical modeling to real hardware Working knowledge of high voltage battery systems, including cell behavior, electrical isolation, thermal runaway, and how mechanical design drives pack safety Experience collaborating closely with electrical engineers on busbars, interconnects, and BMS/sensor integration Proficiency with a major CAD package such as NX, including large assemblies and detailed part design Experience creating and detailing engineering drawings, with a solid understanding of GD&T Strong intuition for manufacturing methods — if you're handed a part, you know how it was likely made and what it costs Practical experience designing, building, and troubleshooting hardware in production environments Clear written and verbal communication Strong time management skills Comfortable pushing at a fast but sustainable pace Comfortable spending time on boats in the field to collect test data Taking full ownership, thinking from first principles, and knowing how to prioritize technical problems efficiently based on the most business value (or business impact) Bonus Qualifications Experience with cell-to-pack or module-to-pack design in automotive, aerospace, or defense applications Familiarity with battery safety and certification standards (e.g. UL 2580, UN 38.3, ISO 6469, ABYC E-13) and thermal runaway propagation mitigation Experience with fluid system design including pump sizing, heat exchanger sizing, and hose/pipe routing Exposure to sheet metal manufacturing, CNC machining, and shop tools Firsthand experience on marine vessels, including knowledge of Coast Guard and ABS regulations Experience with modeling tools such as Matlab and Simulink for thermal and structural sizing Enthusiasm for boating and the water At Arc, we encourage diversity and consider all qualified applicants equally for employment, regardless of background, identity, or status. You’re always welcome to reach out even if you don’t meet many of these qualifications. Passion and aptitude make up for a lot. What we offer The base salary for this role is P3: $150,000 P4: $180,000 annually. Highly competitive equity grants are included with full time offers. As well as semi-annual bonuses tied to your impact, not just your tenure. Additionally, Arc offers top-tier benefits for full-time employees, including: Healthcare benefits — 99% employer-paid medical, dental, and vision Parental leave — 14 weeks fully paid for birthing and non-birthing parents Generous time off — Highly competitive PTO with an opportunity to earn more time with tenure Income protection — Life and disability insurance for all employees Retirement savings — Traditional and Roth 401(k) access Water fund — $500 for you to spend each year to get out on the water, however you choose Professional development — $500 annual reimbursement for professional development and a monthly AI stipend Safety Support- Annual reimbursement for PPE, ergonomic equipment and anything that ensures we keep our crew safe Captain training — Training and access to take Arc boats out with friends and family Office perks — Daily lunches, snacks, and good coffee while onsite Relocation assistance — Available depending on role eligibility. Our values We move with urgency and build with care. We value these five things above all else: Ownership over both your work and the company’s success Empathy for colleagues and for customers Humility in problem solving and collaboration Pragmatism for navigating ambiguity quickly and sensibly Inclusion of different backgrounds, opinions, cultures, and perspectives. We want people who share and embody these values. It is vital that our values align - we’d be happy to elaborate on any or all of these during the interview process.