About Mainspring Mainspring Energy manufactures and delivers fuel-flexible, low-emissions local power solutions that rapidly add new capacity and deliver reliable, affordable, and sustainable electric power. The company began commercial shipments of its Mainspring Linear Generators in 2020 and today has hundreds of megawatts in advanced development and field operations for leading Fortune 500 companies, data centers, and utilities. Mainspring also partners with global energy leaders including AEP, NextEra Energy Resources, Schneider Electric, and more. The core values that ground our work, guide our decisions, and connect us together: Pragmatic Optimism Excellence without Ego Proactive Collaboration
About
the Role Mainspring Energy is seeking a Staff Mechanical Engineer – Battery Design to lead battery pack and module development for current and future energy platforms. As Mainspring's internal battery technical authority, you will help define next-generation battery architectures for future products while improving systems already in production. You'll partner closely with battery suppliers to influence pack and module designs and drive solutions that balance safety, reliability, manufacturability, performance, and cost. You'll influence key decisions across cell integration, thermal management, safety, and system architecture while working at the intersection of mechanical, electrical, and battery engineering. Battery systems are a critical part of Mainspring’s linear generator platform, supporting startup, transient load management, and overall system performance in demanding real-world environments. This role offers the opportunity to solve complex battery engineering challenges, drive supplier strategy, and shape future energy products deployed at scale. The ideal candidate combines deep lithium-ion battery pack expertise with strong supplier-management experience and the ability to translate system
requirements into robust production-ready designs. \n Key
Responsibilities Serve as Mainspring’s technical lead for battery pack and module design. Partner with battery suppliers to review, improve, and influence pack and module architectures. Own battery hardware from
requirements definition through production launch and sustaining engineering. Evaluate battery designs for safety, reliability, manufacturability, thermal performance, lifecycle, and cost. Lead technical reviews of cell integration, interconnect systems, thermal solutions, and safety features. Support supplier selection, design reviews, validation activities, and manufacturing readiness. Develop battery architectures for future generator platforms. Collaborate with Electrical Engineering, BMS, Reliability, Manufacturing, Test, NPI, and Supply Chain teams. Lead root-cause investigations and corrective actions for production, test, and field issues. Provide technical leadership on complex battery-related challenges. Travel to supplier sites as needed to support development and issue resolution.
Qualifications BS or MS in Mechanical Engineering or a related discipline. 10+ years of engineering experience with significant focus on lithium-ion battery pack or module design. Deep understanding of battery pack and module architecture. Experience working directly with battery suppliers and contract manufacturers. Strong knowledge of cell integration and interconnect design, including bus bars, current collectors, voltage sensing, harnessing, and cell terminal joining methods. Experience designing series and parallel battery architectures. Working knowledge of cell construction, dielectrics, fusing, compression systems, and thermal interface materials. Experience with battery thermal management and thermal runaway propagation mitigation. Understanding of battery aging, lifecycle performance, and charge/discharge behavior. Knowledge of environmental durability, vibration, grounding, creepage/clearance, and EMI-related packaging
requirements. Experience supporting validation testing, manufacturing launch, and sustaining engineering. Experience with UL certification of battery systems. Proficiency with SolidWorks and PLM systems. Preferred
Qualifications Experience with prismatic-cell battery systems. Knowledge of BMS integration, contactors, relays, and protection systems. Experience with high-voltage battery or power systems. Experience with battery thermal protection materials and thermal interface design. Familiarity with FEA tools such as Ansys. Experience with products deployed in harsh outdoor environments. Background in EVs, energy storage systems, industrial electrification, power electronics, or other ruggedized energy platforms. \n $172,000 - $203,000 a year This position is onsite at our Menlo Park HQ . The salary will be adjusted to reflect local market conditions based on employee location as well as the experience of the employee. Along with the base salary, Mainspring offers pre-IPO stock options +
benefits. \n Does your experience not meet all of our posted
requirements? Studies have shown that some people are less likely to apply to positions unless they meet every listed requirement. At Mainspring, we are committed to building a diverse, inclusive, flexible, and collaborative environment, so if you want to help us transition the world to clean and affordable electricity, and don’t meet all posted
requirements for a particular role, we’d still love to hear from you. Mainspring can sometimes be flexible enough to shift
responsibilities for the right person, or otherwise identify open or upcoming roles that may better fit your professional background. In more traditional words, Mainspring Energy, Inc is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, or protected veteran status and will not be discriminated against on the basis of disability. This
compensation and
benefits information is based on Mainspring Energy's estimate as of the date of publication and may be modified in the future. We generally do not negotiate on salary once we have made an offer. The level of pay within the range will depend on a variety of job-related factors that may include location, relevant prior experience and/or education, or particular skills and expertise. New hires joining the company tend to be paid within the starting base pay range noted above, with opportunities to increase pay over time based on development of additional skills, competencies, and company-specific knowledge.
