Mechanical Engineer

Job Description

Job Description

Job Description - Mechanical Engineer

Come and join a group of passionate engineers who are working for a vision of clean and affordable energy for everyone. We are looking for very passionate people who believes in renewable energy and its impact on the environment and the sustainability of the planet. We are looking for engineers willing to find solutions to extremely complex engineering challenges. You will join to a team with a culture based in strong values such as trustworthiness, collaboration, dedication, excellence, and Innovation.

sonnen seeks to hire a Mechanical engineer to join the Research and Development team based out of Atlanta Innovation Hub to aid in the product certifications to support our technology development and the execution of projects focused on the development of residential Energy Storage Systems (ESS) and relevant subsystem components. 

Overview

The Mechanical Engineer will lead mechanical design and development for our residential energy storage systems using LFP (lithium iron phosphate) battery technology. You will own designs from concept through production — enclosures, packs, and integrated hardware that need to be safe, durable, cost-effective, and easy to install in the field. The role will be highly collaborative, involving working with electrical, power electronics and controls, and manufacturing teams to ship products that homeowners, installers, and businesses trust.

Responsibilities:

• Lead mechanical design of energy storage and components — enclosures, racks, busbars, structural frames, thermal management hardware, and cell/module mechanical integration
• Develop and review 3D CAD models, drawings, BOMs, tolerance stacks, and BOMs (SolidWorks, Creo, or similar)
• Design and validate enclosure sealing and ingress protection for weather and dust exposure
• Perform structural, thermal, and fatigue analysis (FEA) to validate design integrity under electrical, mechanical, and environmental loads
• Design for manufacturability (DFM), assembly (DFA), and field serviceability, partnering with manufacturing and supply chain on production readiness
• Support thermal management design in coordination with thermal/electrical engineers (cooling plates, airflow, enclosure sealing)
• Ensure designs meet applicable energy storage safety and industry standards (UL 9540, UL 9540A (thermal runaway fire propagation), UL 1973, NFPA 855, seismic/shock/vibration requirements, etc.)
• Drive prototype builds, environmental/reliability testing, and root-cause analysis; iterate designs based on test data and field feedback
• Manage relationships with external vendors/suppliers on custom mechanical components and tooling
• Balance cost, weight, and aesthetics – residential products need to look good on a garage wall, not just perform
• Create and maintain technical documentation, design reviews, and change management records

Qualifications:

• Bachelor's degree in Mechanical Engineering (or related field); Master's a plus
• 5+ years of mechanical design experience, ideally in residential energy storage, EV, renewable energy, or related power electronics/hardware industries
• Strong hands-on experience with 3D CAD (SolidWorks, Creo, or similar) and FEA tools (ANSYS, Abaqus, or similar)
• Solid understanding of sheet metal, extrusions, weldments, castings, and enclosure design (IP/NEMA ratings)
• Familiarity with LFP battery pack mechanical integration and thermal management concepts (passive/active cooling, thermal runaway mitigation and venting) as applied to battery or power electronics systems
• Working knowledge of safety/compliance standards such as UL9540/9540A, UL 1973, NFPA 855, and relevant seismic design codes for residential installations
• Experience taking products from prototype through DFM/DFA and into volume manufacturing
• Good understanding of field installation constraints (wall-mount, ground-mount, conduit/wiring access, technician ergonomics)
• Strong analytical and problem-solving skills; comfortable with hands-on prototyping and testing
• Excellent cross-functional communication and project management skills
• Ability to visit external contract manufacturer, Vendors/suppliers sites as per business needs

Nice to Have

• Direct experience with UL 9540A thermal runaway propagation testing and fire mitigation design
• Exposure to seismic, shock/vibration, or transportation (UN 38.3) qualification testing for Lithium batteries
• Experience with GD&T and formal tolerance analysis
• Experience designing for installer/electrician workflows (NEC compliance considerations, conduit entry points, etc.)
• Background working with contract manufacturers or overseas suppliers