Principal Battery Systems Engineer

• Run multiple product development cycles in parallel — concept through prototype, FAT, field deployment, and revision — without losing depth on any of them.
• Drive cycle cadence: decide what ships when, where the technical risk lives, what gets parallelized vs sequenced.
• Identify and execute the next-generation product moves — higher voltage class, alternate chemistries, new form factors — ahead of customer demand.

• Personally own the hardest pieces of work: novel architectures, first-of-kind designs, advanced component sizing (fuse coordination, busbar thermal optimization, protection coordination across cascaded systems), cabinet thermal modeling, and complex protection schemes.
• Review and approve detailed engineering drawings — SLDs, GAs, schematics, panel layouts — at the level required to sign off, not just consult.

• Own the strategic relationships with key vendors — battery, DC Cabinet, PCS, BoP. Decide the architecture of those relationships: sole-source vs dual-source, co-development depth, IP boundaries.
• Set the technical qualification process used by the team and enforce it. Run the highest-stakes design reviews and resolve the highest-stakes vendor escalations personally.

• Mentor and develop other engineers on the team. Build their technical judgment, not just their throughput.
• Run design reviews. Lead post-mortems on field issues and turn them into product changes.
• Set the cadence and quality bar for ECR/ECN, FMEA, design reviews, and product handoff.

• Represent ON.energy's product engineering externally — customer technical reviews, vendor escalations, industry working groups, certifying bodies, conferences.
• Partner with the commercial team on the most technically complex pursuits and proposals — proposing architectures, defending positions, structuring technical exhibits in LTSAs and supply agreements.
• Brief leadership on technical risk and product roadmap decisions.

• Bachelor's degree in Electrical Engineering, Power Electronics, or a closely related technical field. MS preferred.
• 10+ years of hands-on engineering experience in BESS, power electronics, UPS, or comparable mission-critical industrial power systems, with a demonstrated record of operating with minimal direction in a senior technical role.
• Owned multiple product development cycles end-to-end and independently. You've personally taken more than one product from concept through prototype, FAT, field deployment, and revision — and the products are still in the field.
• Architecture-level decision authority on previous BESS or DC equipment. You've made the trade-off calls others built around, not just executed someone else's architecture.
• Deep, demonstrable skill in detailed component sizing — fuse coordination, busbar sizing, protection device selection, thermal sizing for enclosed cabinets — at the level required to sign off on production designs.
• Fluency producing and reviewing SLDs, GAs, schematics, and panel layouts; expert with AutoCAD or equivalent E-CAD; comfortable across mechanical drawings.
• Strong track record running strategic vendor relationships through design, FAT, serial production, and post-deployment escalation.
• Excellent written and verbal communication — specs, technical positions, design review leadership, board-level briefings.
• Willing to travel up to 25–30% for FAT inspections, site commissioning, customer engagements, and vendor reviews.

• Direct experience with data center / UPS / mission-critical power or utility-scale BESS at the architecture level.
• Active involvement in standards bodies (UL, IEC, NFPA, IEEE working groups, CSA TC committees) or technical conference contributions.
• Patents, peer-reviewed publications, or other evidence of recognized technical depth in the field.
• PE license.
• Familiarity with UL 9540 / 9540A, NFPA 855, IEC 62619, IEEE 1547, NEC Article 706, plus the relevant codes for target markets.
• Experience standing up or scaling structured PLM, ECR/ECN, and design-review processes.
• Multi-domain depth — BMS / cell engineering, PCS / power electronics, thermal / mechanical — alongside the EE core.

For US-based roles - What you’ll get:

• Competitive salary + annual performance-based bonus eligibility
• Medical, dental, and vision insurance
• 401(k) with company match
• Paid time off and company holidays

For Mexico-based roles - What you’ll get:

• Competitive salary + annual performance bonus eligibility
• Christmas Bonus (Aguinaldo): 30 days
• Major medical expenses and life insurance
• Paid time off and holidays (per local policy)

For all roles:

• Professional development and growth opportunities
• Opportunity to grow with a mission-driven team shaping the future of clean energy
• Equal Opportunity: ON.energy is committed to equal employment opportunity and to maintaining a work environment free of harassment, discrimination, or retaliation.
• Accommodations: If you need an accommodation during the application process, email recruitment@onenergystorage.com
• Benefits vary by role and location and are subject to change.

Agency Notice: ON.energy does not accept unsolicited resumes from staffing agencies, search firms, or third-party recruiters.

Resumes submitted without a fully executed Master Services Agreement (MSA) and a written request from an authorized member of our Talent Acquisition team will be considered the property of ON.energy.

No placement fees or compensation will be paid for unsolicited candidate submissions.