Junior Simulation Engineer - EMS

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.

Role Summary

At ON.energy, the Simulation Engineer for Battery Energy Storage Systems (BESS) is responsible for building, running, and validating simulation environments that ensure our energy management software performs correctly before it ever touches real hardware. This is a simulation-first role where the primary deliverables are high-fidelity Software-in-the-Loop (SIL) and Hardware-in-the-Loop (HIL) test environments that give our engineering teams confidence in every algorithm, control loop, and protection function we deploy. 

The ideal candidate is an early-career engineer with a solid foundation in dynamic systems, power electronics, or control theory, and a hands-on curiosity for building models that accurately reflect real BESS behavior. This role offers direct mentorship from senior R&D engineers and access to industry-leading real-time simulation hardware. 

Key Responsibilities 

SIL Simulation & Validation 

• Develop and maintain Software-in-the-Loop (SIL) environments in MATLAB/Simulink to validate energy management algorithms, protection logic, and control strategies prior to hardware integration. 
• Build high-fidelity battery system models in Simulink — including cell electrochemistry, thermal dynamics, State of Charge (SoC), and State of Health (SoH) — and continuously improve model fidelity against measured data. 
• Design and execute automated regression test suites in MATLAB to verify algorithm correctness across operating modes, edge cases, and fault scenarios. 
• Analyze simulation outputs, document findings, and communicate results clearly to the broader engineering team. 

 HIL Testing & Integration 

• Support the setup, configuration, and operation of Hardware-in-the-Loop (HIL) test environments, interfacing real EMS and BMS hardware with real-time simulation platforms. 
• Establish reliable communication between hardware controllers and simulation environments over industrial protocols such as CAN, Modbus, DNP3, or IEC 61850. 
• Execute functional, edge-case, and fault-injection test campaigns against EMS control logic, documenting pass/fail results and root-cause analyses. 
• Assist in debugging hardware-software communication issues and contribute to the continuous improvement of the HIL test infrastructure. 

 Model Development & Algorithm Support 

• Collaborate with senior engineers to develop and refine Simulink models of battery behavior, inverter dynamics, and grid interaction for use across SIL and HIL environments. 
• Assist in prototyping energy management strategies including peak shaving, frequency regulation, and charge/discharge optimization — running simulation campaigns to evaluate performance. 
• Contribute to model-based design workflows in Simulink, supporting automatic code generation and deployment pipelines. 

 Documentation & Collaboration 

• Maintain detailed technical documentation: test plans, test reports, model specifications, and simulation environment setup guides. 
• Participate in design reviews and contribute to internal knowledge-sharing and lessons-learned sessions. 
• Work cross-functionally with hardware, software, controls, and field engineering teams throughout the product development lifecycle. 

Key Requirements

• Entry-Level, 0–2 years of experience
• Hands-on experience with MATLAB and Simulink for model-based design and system simulation. Coursework, capstone, or internship experience is accepted.  
• Demonstrated understanding of Software-in-the-Loop and Hardware-in-the-Loop testing methodologies — what they validate, when to use each, and how they fit into a V-model development process.  
• Foundational knowledge of battery systems, power electronics, or energy storage technologies. Familiarity with SoC, SoH, and basic BMS functionality.  
• Coursework or project experience in control theory, embedded systems, or mechatronics. Ability to interpret and validate control logic behavior in simulation.  
• Ability to write clear technical documentation and communicate simulation findings to multi-disciplinary engineering teams.  
• Exposure to Hardware-in-the-Loop testing concepts and real-time simulation environments. Familiarity with how EMS/BMS hardware interfaces with simulation platforms is a plus.  
• Familiarity with CAN, Modbus RTU/TCP, DNP3, or IEC 61850 — enough to understand tag structure and how data availability shapes simulation interfaces.  
• Experience with MATLAB scripting for test automation, post-processing, and regression pipeline development. Python familiarity is a plus.  
• Bachelor's degree in Electrical Engineering, Mechanical Engineering, Systems Engineering, or a related field — or equivalent professional experience.

Preferred Experience

• Experience with BESS, inverters, or distributed energy resources (DER) and familiarity with their operational state models and protection logic. 
• Ability to read and interpret single-line diagrams and understand basic power system concepts — important context for modeling accurate BESS behavior. 
• Exposure to version control for simulation projects (e.g., Git-based workflows for MATLAB/Simulink models). 
• Knowledge of Li-ion or LFP battery chemistry and cell-level behavior. 
• Experience with code generation from Simulink models (Simulink Coder) for deployment to embedded or real-time targets. 

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.