Principal Product Engineer - BESS & DC Cabinets

ON.energy is building the power infrastructure that makes the AI era possible. As AI demand surges past what the grid and traditional data centers can support, ON.energy provides a new class of power technology proven at gigawatt scale and trusted by the world’s leading cloud and AI companies. Our systems are already deployed across 2.5 GW of hyper-scale campuses, validated by top U.S. national labs, and certified for grid-safe operation by major utilities. With real products in the field, we’re scaling faster than the grid can, transforming power from a bottleneck into a competitive advantage for the companies building the future.

Principal Engineer — BESS DC Cabinet

Role Overview

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.

What You'll Own

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.

Multi-Product Development

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.

Required Qualifications

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 …