Serentica Renewables Battery Engineer Interview: Rounds, Questions and Preparation

What the job involves

Battery engineers in EV and cleantech companies design, test, and optimise battery packs and battery management systems for electric vehicles and stationary storage. On a typical day, you might analyse cell test data, run simulations, troubleshoot BMS issues, or coordinate with suppliers and testing teams. Freshers often start with cell characterisation, pack assembly support, or validation testing before moving to design ownership.

Role and technical knowledge

1. 1

   Explain the difference between Li-ion NMC and LFP cells. Which would you choose for a two-wheeler EV in India and why?

   Compare energy density, cycle life, thermal stability, and cost. Mention Indian conditions like high ambient temperature and duty cycles.

2. 2

   What is a Battery Management System and what are its key functions?

   Cover cell monitoring, SoC/SoH estimation, cell balancing, protection (overvoltage, undervoltage, overcurrent, temperature), and communication.

3. 3

   How would you estimate State of Charge (SoC) of a Li-ion cell? Discuss at least two methods.

   Mention coulomb counting, open-circuit voltage (OCV) method, and Kalman filter-based estimation. Note limitations of each.

4. 4

   What are the key safety tests a battery pack must pass for EV certification in India?

   Refer to AIS 156 for battery safety, including vibration, thermal shock, overcharge, short circuit, and fire resistance tests.

Practical scenarios and problem solving

1. 5

   A battery pack in a test vehicle is heating up more than expected during fast charging. How would you diagnose and address this?

   Check cell internal resistance, cooling system design, charging profile, and ambient conditions. Suggest thermal management improvements or charge rate adjustment.

2. 6

   You observe that one cell in a series string is consistently lower in voltage than others after a few cycles. What could be the cause and what would you do?

   Consider cell mismatch, faulty connection, or BMS balancing issue. Suggest cell replacement, improved balancing strategy, or supplier quality check.

3. 7

   How would you size a battery pack for a 48V, 2 kWh electric scooter? Outline your steps.

   Calculate required capacity in Ah, choose cell configuration (series/parallel), consider voltage range, space, weight, and cost constraints.

4. 8

   You need to validate a new cell supplier for your battery packs. What tests and parameters would you include in your evaluation?

   Cover capacity, internal resistance, cycle life, temperature performance, safety tests, and consistency across batches. Mention sampling and data analysis.

Behavioural and teamwork

1. 9

   Describe a project where you worked in a team to solve a technical problem. What was your role?

   Use STAR method. Highlight your contribution, how you collaborated, and the outcome. Relate to battery or EV projects if possible.

2. 10

   Tell me about a time you had to learn a new tool or technology quickly for a project.

   Show adaptability and initiative. Mention specific tools like MATLAB, Python, or testing equipment and how you applied them.

3. 11

   How do you handle disagreements with a senior engineer or mentor on a technical decision?

   Demonstrate respect, data-driven discussion, and willingness to listen. Emphasise finding the best solution through evidence.

4. 12

   Give an example of a mistake you made in a lab or project and what you learned from it.

   Be honest, focus on the lesson and how you improved processes or safety awareness afterwards.

HR and motivation

1. 13

   Why do you want to work in the EV and cleantech sector, especially with a company like Serentica Renewables?

   Show passion for sustainability, awareness of India's renewable energy and EV goals, and alignment with the company's focus on clean energy solutions.

2. 14

   Where do you see yourself in three years as a battery engineer?

   Express interest in growing into design ownership, specialising in BMS or thermal management, and contributing to innovative projects.

3. 15

   Are you willing to relocate or work at project sites or manufacturing plants if required?

   Be flexible and positive. Mention willingness to travel for testing or supplier visits if it helps you learn and contribute.

4. 16

   What are your salary expectations for this role?

   Research typical fresher salaries in the EV sector in India. Give a reasonable range and emphasise learning and growth opportunities.