Principal Battery Storage Engineer

ON.energy is building the backbone of energy and AI infrastructure powering grid-safe data centers and mission-critical facilities. The company supplies and operates hyperscale power systems that solve the toughest resilience challenges, delivering custom solutions for AI data centers, mission-critical facilities, and front-of-the-meter assets. ON recently announced a 5GW partnership, with 3GW currently under construction across multiple hyperscale data center campuses. With patented technology and proprietary software, ON.energy

develops projects worldwide that set new benchmarks for resilience.

We're looking for a Principal Engineer to set the technical direction for our BESS and DC Cabinet product lines and to own the product roadmap across multiple concurrent development cycles. This is the senior technical voice on the product team: you'll architect new products, resolve the hardest engineering trade-offs, set the engineering standards others work to, and represent ON.energy's product engineering externally — to vendors, customers, certifying bodies, and the broader industry.

You should be comfortable operating with minimal direction, holding the bar on technical quality, and moving multiple product cycles forward in parallel without losing the thread on any of them.

Architecture & Technical Direction

• Set the architecture for the BESS and DC Cabinet product lines and own the technical roadmap across multiple concurrent product cycles.
• Make the hard trade-off calls — cost vs reliability, performance vs lead time, standardization vs customization — and document the reasoning so future decisions inherit context.
• Define the engineering standards, design rules, and review gates that other engineers on the team work to. Own the product-engineering bar.
• Approve major design changes; act as the final technical authority on the change baseline.
• 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.

Detailed Engineering Depth

• 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.

Vendor & Supply Chain Strategy

• Own the strategic relationships with key vendors — DC Cabinet, battery, 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.

Engineering Leadership & Mentorship

• 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.

External & Cross-Functional Representation

• 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…