A checklist for choosing an EV battery supplier in India

The 12 questions

1. Which AIS 156 phase have you certified to, and at which ARAI lab?
2. What is your cell sourcing strategy — direct from cell manufacturer, or through a trader?
3. Do you assemble the pack in India, or just import + relabel?
4. What is your BMS firmware update mechanism — OTA via the vehicle, or service-only?
5. What is your warranty failure rate per 10,000 packs in the first 2 years?
6. What is your pack-level cycle life specification, measured at 80% DoD?
7. What is the field-replaceable unit — module, full pack, or only at the cell level?
8. Do you provide pack telemetry data to the OEM, and at what granularity?
9. What is your service network — own service centers, partner network, or none?
10. What is your IP rating, and what is the test methodology that produced it?
11. What is your lead time at full production volume?
12. Show me your last three thermal incident reports and the corrective actions taken.

Why these questions matter

Each one tells you something a marketing brochure won't. Question 12 is the most useful — anyone who says "we've never had a thermal incident" is either lying or doesn't have enough volume to know yet. Real suppliers learn from incidents and improve.

What we'd want to be asked

We get asked these regularly. The ones that surprise us are good signals: question 11 (lead time at volume) tells us the buyer has ramp planning experience. Question 8 (telemetry granularity) tells us they care about long-term fleet health. Question 12 (incident reports) tells us they've worked with mature suppliers before.

If you're sourcing your first EV battery supplier, walking through this list will save you a quarter of pain.