Battery Engineer – Lithium-Ion Batteries, Modeling, Testing & BESS Integration

About Battwoo

Battwoo is an international deep-tech startup developing energy storage systems based on second-life electric vehicle batteries. Our headquarters are in Paris, while our R&D and engineering activities are based in Madrid, where we design, test, integrate and validate our battery systems.

The Role

We are looking for a Battery Engineer to join our technical team on-site in Vallecas, Madrid.

The role combines battery modeling, testing, characterization, data analysis and BESS integration. The candidate will work with lithium-ion batteries, experimental data, laboratory equipment and real battery systems. As an early-stage startup, we are looking for someone adaptable, hands-on and autonomous, able to take ownership of technical tasks and contribute across different engineering areas. We are open to candidates from different engineering backgrounds — electrical, mechanical, industrial, electronics, energy or similar — but the key requirement is strong technical knowledge of lithium-ion batteries.

Main requirements:

• Engineering degree.
• At least 3 years of experience working with lithium-ion batteries.
• Strong understanding of battery fundamentals: SoC, SoH, ageing, degradation, safety, power and capacity.
• Experience in at least one of the following areas: battery testing, modeling, characterization, system integration, BESS or battery packs.
• Programming skills in Python, MATLAB or similar tools.
• Ability to analyze experimental data and extract technical conclusions.
• Hands-on attitude and availability to work on-site in Vallecas, Madrid.
• Advanced English. Spanish and/or French will be highly valued.

Highly valued:

• Formula Student or similar hands-on engineering competition experience.
• Second-life batteries.
• BESS design and integration.
• Battery manufacturing, assembly or pack design.
• Electronics, power electronics, BMS/EMS or control software.
• Cyclers, climatic chambers, DAQ systems or test benches.
• MATLAB/Simulink, Python data analysis or test automation.
• IEC standards related to batteries or stationary energy storage.

What we offer

This is a key technical role with real impact from day one, strong growth potential and hands-on work with real battery systems.

There may also be a future path towards an Industrial PhD focused on modeling and predicting ageing in second-life batteries, depending on funding and academic collaboration opportunities.