01How the course is made
- Explain, then let you try. Each lesson states what you will be able to do, explains it in plain language, and gives you something to change and watch.
- Every number is tested. Calculators and worked examples come from the same functions as the open-source
battery_corePython package, and automated tests check that the numbers on the pages match the code. - Every claim has a source. Lessons end with their references — textbooks, peer-reviewed papers and industry production guides — with links where they exist.
- Every model says what it is. Teaching models show direction and shape. Each lesson and lab states its assumptions and limits, so a simplification is never mistaken for a prediction.
- Free and private. No account, no tracking of your answers: progress and exam results stay in your browser.
02Open source
The site, the labs and the Python package are developed in the open as Battery Core, a project of Lemonergy. They are licensed under the GNU Affero General Public License, version 3 or later, with attribution to Lemonergy; a commercial licence is available for closed products. See Licensing for what each one allows.
03How to cite
If you use the course in teaching or writing, please cite it as:
Lemonergy. Battery Cell Foundations (online course). Lemonergy Learn, 2026. https://learn.lemonergy.com/
To cite a single lesson, use its title and address instead, and add the date you read it.
04Frequently asked questions
Is the course free?
Yes. Every lesson, lab, quiz and the final exam is free, with no account and nothing to install.
Do I need a background in chemistry or engineering?
How long does it take?
About five hours for everything, at your own pace. The core path — Lessons 1, 2, 3 and 4, the checkpoint and the final exam — takes about three and a half hours; Lessons 0, 1B and 3B are optional.
Is my progress saved?
Yes, in this browser only. Lessons you mark complete, your practice-quiz results, your exam result and the name on your statement are kept in your browser’s local storage, and nothing is sent anywhere. Another browser or device starts fresh, and clearing site data clears your progress.
Do I get a certificate?
Pass the final exam and you can print a statement of completion with your name, score and date. It is generated in your own browser, so it is a personal record — not an accredited certificate, and not verified by Lemonergy.
How accurate are the simulators and models?
They teach direction, shape and rough size. Process sequences and operating ranges come from published sources such as the PEM RWTH Aachen and VDMA production guides; outputs such as capacity estimates or aging curves are teaching relationships, not calibrated predictions. Every lesson and lab says what its numbers are. Do not use them for design or safety decisions.
How is the content checked?
Every lesson lists its sources, every calculator mirrors a tested function in the open-source battery_core Python package, and numbers printed on the pages are checked against that code automatically. New lessons are fact-checked against their sources before they are published.
Can I use the material in my teaching or at my company?
Yes, under the GNU AGPL, version 3 or later, with attribution to Lemonergy. Building it into a closed product or service needs a commercial licence. The licensing page explains both.
Can I run the code myself?
Yes. The calculations are a tested, open-source Python package, and Lessons 2 and 4 and Fick’s law each link to a notebook you can run in your browser without installing anything.
What comes next?
Chapter 2 is planned: equivalent-circuit models, from open-circuit voltage and internal resistance to RC models, parameter identification and validation. The learning roadmap shows the plan.
I found a mistake. How do I report it?
Thank you — please email info@lemonergy.com with the page and the sentence.
05Contact
Questions, corrections and licensing enquiries: info@lemonergy.com. More from Lemonergy at lemonergy.com.