In the summer of 2022, a string of electric two-wheeler fires made national headlines and did something rare in Indian industry — it forced regulation to move faster than the market. Within months, the Ministry of Road Transport and Highways (MoRTH) issued sweeping amendments to AIS-156 and AIS-038 (Rev 2), the standards that govern EV powertrain and battery safety. The phased rollout — Phase 1 effective 1 December 2022 and Phase 2 effective 31 March 2023 — fundamentally changed what a legal, safe lithium-ion battery pack looks like in India.

But here is the uncomfortable truth that fleet operators, OEMs, and informed buyers have learned since: a certificate on the wall is not the same as safety in the pack. Two batteries can both claim AIS-156 compliance and behave very differently when a cell fails on a 47°C afternoon in Kanpur. This article explains what the standard actually requires, what thermal runaway really is, and the engineering details that separate a genuinely safe pack from a merely compliant one.

What AIS-156 Actually Is (and What It Isn’t)

AIS-156 is India’s safety standard for L-category electric vehicles — two-wheelers, three-wheelers, and quadricycles — and their Rechargeable Electrical Energy Storage Systems (REESS). Its sibling, AIS-038 (Rev 2), applies the same philosophy to M and N category vehicles (cars, buses, trucks). Both take a system-level approach: the battery is not tested as a standalone box, but as part of the vehicle, because that is how failures actually happen.

What the standard is not: a performance benchmark. AIS-156 says nothing about range, cycle life, or energy density. A pack can pass every clause and still be a mediocre battery. Safety is the floor, not the ceiling — which is exactly why the details of how a manufacturer meets the standard matter so much.

Phase 1 vs Phase 2: The Two Waves of Compliance

The September 2022 amendments were deliberately split to give the industry time to build test capability.

Phase 1 (December 2022) covered the “design hygiene” items — things a competent manufacturer should already have been doing:

• Pack traceability: every pack traceable to its cell batch and production lot, so field failures can be isolated and recalled.
• Additional safety fuse at the pack level, independent of the BMS, so a catastrophic fault blows the fuse rather than the cells.
• Protection against regenerative braking overcharge — a subtle but real failure mode where regen current pushes a full pack into overvoltage.
• Minimum cell-to-cell spacing to slow heat transfer between adjacent cells.
• A microprocessor-based BMS with over-charge, over-discharge, over-current, over-temperature, and short-circuit protection as mandatory functions.

Phase 2 (March 2023) is where the standard got serious — and where most marginal manufacturers were exposed:

• Thermal propagation test (Annexure 8J/8K): the defining requirement. A single cell inside the pack is deliberately driven into thermal runaway (via heating or nail penetration). The pack must show no fire and no explosion triggered by that single-cell event. One cell may die; the pack may not.
• IPX7 water ingress protection: the REESS at 100% state of charge must survive immersion in one metre of water for 30 minutes with no fire, explosion, or dangerous leakage — the monsoon test, essentially.
• A minimum of four temperature sensors distributed inside the pack, so the BMS sees thermal anomalies early rather than after the fact.
• Audio-visual thermal event warning: the vehicle must actively warn the rider when a thermal event begins, giving them time to get away.
• Earth leakage detection in the charger, so insulation faults don’t turn a charging session into an electrocution or fire risk.
• EMC testing of the BMS per AIS-004 — the BMS must keep working correctly amid the electromagnetic noise of a real vehicle.
• Cell-level testing to IS 16893 from a NABL-accredited lab, pushing accountability down to the cells themselves, not just the assembled pack.
• Active parallel circuits for packs with parallel strings, preventing one failing string from being force-fed current by healthy ones.

Thermal Runaway: The 90 Seconds That Matter

To appreciate why the thermal propagation test is the heart of AIS-156 Phase 2, it helps to understand the failure sequence it simulates.

A lithium-ion cell stores energy in a chemistry that is, under abuse, self-oxidising. When a cell is damaged — by an internal short circuit from a manufacturing defect, dendrite growth, mechanical crush, or extreme overcharge — internal temperature climbs past roughly 130–200°C depending on chemistry. The separator melts, the electrodes touch, and the cell enters thermal runaway: an exothermic chain reaction that vents flammable gases at 400–600°C+ and cannot be stopped once started.

A single cell in runaway is dangerous but survivable. The catastrophe is propagation — when the heat and flames from one failed cell push neighbouring cells over the edge, cascading through the pack until the entire pack vents and burns. This is what turns a cell defect into a vehicle fire, and it is precisely what the Annexure 8J test forbids.

Breaking the chain is an engineering problem with several levers:

• Cell spacing and thermal barriers slow conductive heat transfer between cells.
• Chemistry choice matters enormously — LFP and LMFP cathodes release far less energy and no oxygen in runaway compared to high-nickel NMC, dramatically widening the margin before propagation begins.
• Vent path design channels hot gases away from neighbouring cells and out of the enclosure.
• Early detection via distributed temperature sensors lets the BMS disconnect the pack and trigger the audio-visual warning before propagation starts.

This is why two “compliant” packs differ. Passing the test once, on a good day, is different from engineering a pack where propagation is architecturally difficult.

Inside a production lithium-ion pack: modules, busbars, and the BMS hardware that AIS-156 regulates. Photo: RudolfSimon / Wikimedia Commons (CC BY-SA 3.0).

The Indian Operating Envelope

AIS-156’s extra requirements exist because Indian conditions are uniquely hostile to lithium-ion packs:

• Ambient heat: sustained 40–47°C summers push cell temperatures close to chemistry limits even before load is applied.
• Monsoon flooding: streets flood axle-deep for hours; IPX7 isn’t a formality, it’s a survival spec.
• Grid and charger quality: voltage swings and substandard aftermarket chargers stress packs through every charge cycle.
• Duty cycle abuse: e-rickshaws and delivery two-wheelers run 100–150 km daily, often fast-charged, with zero rest between shifts.
• Dust and vibration: unpaved routes hammer pack enclosures and connectors for years.

The real test track: an e-rickshaw in Meerut. Indian packs face heat, dust, flooding and relentless commercial duty that no foreign test cycle simulates. Photo: Libreravi / Wikimedia Commons (CC BY-SA 4.0).

A battery designed for European test cycles will fail Indian reality. Safety engineering has to start from the operating envelope, not the lab bench.

How Ipower Engineers Safety Into the Pack

At Ipower Batteries’ Kundli, Haryana facility, AIS-156 compliance is treated as the starting line. The Rugpro range — in LFP and cobalt-free LMFP chemistries — is built around the failure modes the standard targets:

• Chemistry-led safety: LFP and LMFP cathodes offer inherently superior thermal stability, with runaway onset temperatures significantly higher than NMC — the single biggest structural advantage against propagation.
• Multi-sensor BMS architecture: microprocessor-based BMS with distributed temperature sensing, per-string protection, pack-level fuse, and regen overcharge protection — exceeding the Phase 1/2 functional list.
• Ingress-engineered enclosures: sealed pack designs validated against water and dust ingress for monsoon and dust-storm duty.
• Government-approved R&D and testing labs on site, so capacity, charge-discharge, vibration, and safety verification happen on every batch — not just at certification.
• IATF 16949:2016 and ISO-certified quality systems, meaning the process discipline that produces a compliant pack today still produces it in the 50,000th unit.

A Buyer’s Checklist: Questions That Reveal Real Safety

Whether you’re an OEM qualifying a supplier or a fleet owner buying vehicles, these questions cut through the marketing:

1. “Show me the thermal propagation test report” — not just the certificate. Which lab? What trigger method? What did the pack look like after?
2. “Which chemistry, and why?” — A supplier who can’t explain why LFP/LMFP vs NMC for your duty cycle is selling a SKU, not engineering a solution.
3. “How many temperature sensors, and where?” — Four is the legal floor; placement matters as much as count.
4. “What happens to the BMS during EMC events and charger faults?” — Ask for the AIS-004 EMC and earth-leakage evidence.
5. “How are cells sourced and batch-traceable?” — Traceability is what turns a field incident into a contained recall instead of a brand-ending scandal.
6. “What’s your field failure rate and service response?” — Safety is also about what happens after a pack misbehaves. A manufacturer with a deep service network (Ipower operates 200+ service centres across India) closes the loop that regulation can’t.

The Bottom Line

AIS-156 Phase 2 raised the floor for the entire Indian EV industry — and it worked. Thermal propagation testing, IPX7, distributed sensing, and functional BMS requirements have made the worst packs illegal. But the standard defines minimum survival, not excellence. The safest battery is the one whose manufacturer treats the standard as a floor: choosing stable chemistries, engineering against propagation architecturally, testing every batch, and standing behind the pack with a real service network.

That is the difference between a certificate and a commitment.

Ipower Batteries designs and manufactures AIS-156-compliant Rugpro lithium-ion battery packs in LFP and LMFP chemistries at its IATF 16949-certified facility in Kundli, Haryana — backed by 200+ service centres across India. To discuss battery safety for your EV program, contact the Ipower engineering team.