Who decides your battery is healthy

Somewhere around page 332 of the Tata Nexon.ev owner's manual, inside the battery warranty section, there is a sentence most owners will never read.

"after a maximum of four DC / opportunity charging cycles, you must use AC charging to 100% State of Charge for the optimum performance of the high voltage battery pack."

Read that as a condition rather than a tip, because that is where it sits. It appears in five of Tata's seven EV owner manuals: Nexon.ev, Harrier.ev, Curvv.ev, Punch.ev and Tiago.ev. It is absent from the Sierra.ev and from the Tigor.ev. Three of the seven go further and add a limit on how often the car may complain about how you charge: "Vehicle shall not have more than 2 warnings related to EV charging pattern between two service intervals."

If you have a wall box at home, none of this will ever trouble you. If you live in a flat and charge where you can, which is most Indian EV owners, you are being held to a ratio nobody told you about.

And you have no record of your own ratio. Six of those seven manuals say who does. The warranty depends on you keeping the connected car subscription alive, because, in the manual's words, "IRA.ev subscription maintenance is crucial for telemetry data to be transferred back to TPEM to allow visibility of the last steady state of the HV Battery for application of the HV Battery Warranty."

So the company that pays the claim is the company that watches the car, and the owner is the only party to the contract who cannot see the evidence.

This is not about one manufacturer

We read them all. Around 45 models across 25 makers, four wheel and two and three wheel, at the primary document, over one day in September 2026. Not one press article, not one aggregator. Where a maker publishes nothing, we wrote down that it publishes nothing.

The pattern is the same everywhere, and it has four steps.

The maker sets a number. Usually 70 percent state of health. Tata, Mahindra, Toyota, Mercedes-Benz, Ather, Ola, Revolt and Altigreen all publish one. Kia publishes it for the Carens Clavis EV and the Syros EV, and for the EV6 and EV9 it publishes a clause titled a capacity warranty containing no percentage at all, until you open the owner's manual, where the 70 percent sits on page 592 of 605.

The maker measures it. By a method it does not disclose. Of every model we read, exactly one discloses how state of health is determined: the Altigreen neEV TEZ, whose pack is warranted by Exponent, which specifies a CC-CV profile at 54A. Every other maker publishing a threshold leaves undefined the procedure that produces the number the threshold is compared against. No temperature condition. No state of charge precondition. No rest period. No instrument. No standard.

Ather says capacity is judged "as measured by Ather's standard testing procedure", and then never describes the procedure. Ola says "Battery Health certification will be done by the company only after the scooter has been driven for more than 10,000 kms."

The maker decides. Tata: repair or replace, "to be decided at sole discretion of Tata Passenger Electric Mobility Limited". MG: "JSW MG MOTOR's decision is final and binding on the Owner of the vehicle in all warranty matters." Hyundai: "HMIL's decision is final and binding." Kia: "KIN reserves the right for the final decision in all warranty matters." Ampere: "The right to determine whether the part needs repair rests solely with Ampere only." Mahindra reserves the right to appoint the inspecting engineer, including the one its own guide calls "an independent consultant engineer".

And nobody outside checks. In every row of the audit, across every maker, the answer to whether the owner may independently verify or dispute the reading is the same. It is not addressed. Not refused, not conditioned, not appealable. Simply not a thing the documents contemplate.

Mercedes-Benz is the only partial exception, and only on half the sum. It records rated capacity at production, prints it on a label on the pack, and will give it to you at any authorised dealer. So a Mercedes owner in India can learn the denominator of their own degradation calculation. No maker in India publishes the numerator method.

Three makers, three different postures

Reading every manual from the three largest, rather than one each, turned out to matter.

Tata has a number and varies the conditions around it. Seven manuals, and the DC charging cap is in five, the telematics requirement in six, the charging warning limit in three. The Sierra.ev, the newest car, keeps the 70 percent floor and the telematics requirement and drops the DC cap entirely. We searched its charging section for any equivalent wording and found only ordinary explanation of how fast charging works. Whether that is a deliberate change of policy is a question for Tata, not a conclusion for us.

Mahindra has a number and applies it consistently. All four warranty guides, for the XEV 9e, BE 6, XEV 9S and BE 6 FE, carry the same tiered 85, 75 and 70 percent structure and the same charging exclusions. None of the four caps DC fast charging.

MG has no number. We read the full text of the ZS EV, Comet EV and Windsor EV Service and Warranty Manuals, and there is no percentage figure in any of them. Cover triggers where the pack "has suffered a capacity drop below acceptable degradation according to the use and ageing of the vehicle". The exclusion removes cover "If the degree of degradation of the high-voltage battery is within the normal aging level". Neither phrase is defined anywhere in the document.

Those two clauses are the same clause facing in opposite directions, and the only party who can tell you which one applies is the party whose decision the same manual calls final and binding.

There is no standard, and the Government has written that down

We went looking for the Indian standard that defines how state of health is measured. AIS-038 Revision 2, AIS-156, AIS-040 Revision 1 and AIS-049 Revision 1, read at ARAI's own server. All four are type approval instruments. They test a new vehicle or a new pack for electrical safety, thermal and mechanical abuse, fire resistance, overcharge and over-discharge protection, and, in AIS-040, a laboratory range figure on a new car. None of them measures a battery already in service. IS 17855:2022 is bench performance testing of a new pack.

No instrument we could find requires a maker to publish its warranty terms, declare a floor, or disclose a method. The Consumer Protection Act 2019 makes it an unfair trade practice to give a warranty of "length of life" that is "not based on an adequate or proper test", which is a duty to substantiate rather than a duty to tell you, and there is no prescribed test to substantiate against.

The clearest statement of the gap is the Government's own. The draft Battery Pack Aadhaar guidelines from the Ministry of Road Transport and Highways put State of Health in the battery's dynamic data set, held on a central server, and then say this:

"The detailed methodology for validating SOH needs to be separately developed by the Government."

A field, with no method.

For contrast, the EU battery passport becomes mandatory on 18 February 2027, and Article 14 of Regulation 2023/1542 requires state of health and expected lifetime parameters to be held in the battery management system with read only access granted to the owner, to independent operators and to waste operators, expressly including for evaluating residual value. Europe prescribes the parameters and mandates the access. India has named the field and deferred the method.

What happens when somebody argues

We looked for a decided case. There is one that is directly on point, and it went the way you would expect.

A man bought a battery operated e-rickshaw for Rs 1,50,000 in May 2017 on a representation that it would run 80 to 100 km on a six hour charge. It ran about 20. The battery was replaced on 23 May, on 5 July, on 9 July and again on 1 August, and nothing improved. The District Commission ordered a refund with interest.

The Madhya Pradesh State Commission set that aside and dismissed the complaint. First Appeal No. 358 of 2021, order of 19 September 2024. The reason, in the Commission's words: "In absence of expert evidence it cannot be concluded that the subject e-rickshaw was having manufacturing defect."

He lost because he could not prove it. There is no prescribed Indian method by which he could have proved it.

And if he had wanted to try, the queue is 5,74,333 cases pending as of January 2026, with 169 President and 379 Member posts vacant at district level, in a system whose statute asks for disposal within five months where testing is required and uses the words "endeavour shall be made".

The shape of the problem

Put the pieces next to each other.

You are held to a standard of charging conduct, on equipment and an electricity supply you do not own or control. The threshold that decides your claim is set by the maker, where it is published at all. The measurement is taken by the maker, by a method no document describes. The decision is the maker's, at its sole discretion, final and binding. No Indian standard defines the measurement. The regulator has written down that the method still needs to be developed. And the one owner who took it to a commission lost for want of evidence that nothing in the country is set up to produce.

None of that is an accusation of bad faith. Every maker here is operating inside a vacuum that nobody created on purpose. A warranty needs a threshold, a threshold needs a measurement, and in the absence of a standard the only measurement available is the maker's own. That is not a conspiracy. It is what happens when the instrument does not exist yet.

But it does mean something concrete for anyone buying an EV in India this year. The most valuable component in the car is warranted against a number you cannot see, measured by a method you cannot read, assessed by the party that pays if the answer goes your way.

Where we come into this

We are building an independent measurement of charging reliability in India, from the driver's side. The first Mumbai index publishes on 5 November 2026.

This piece is not that. We have measured nothing here. Everything above is what 25 manufacturers and the Government of India have published about themselves, read at source, on 22 September 2026, with the absences recorded as carefully as the presences.

We publish it because the same gap runs through both. A charging network reports its own uptime. A manufacturer measures its own battery. In each case the number that matters most is produced by the party with the most at stake in the answer, and in each case the reason is not malice, it is that nobody else is counting.

One of those two we intend to fix.

The table

The audit is published as an open dataset, under CC BY 4.0, at github.com/voltu-energy/india-ev-battery-warranty.

Three files. One row per model with the structured terms. One row per clause, quoted verbatim, each carrying the exact models whose documents we read it in. And one row per source document, with its URL, the date we read it, and how we reached it, including which ones were blocked to automated retrieval and had to be opened in a browser.

There are no blank cells, because a blank would hide the most interesting thing in it. Six absence codes instead, and the distinctions matter: NOT_FOUND means we could not find the document, NOT_STATED means we read it and it is silent, NOT_DISCLOSED means a threshold is set with no method described, and NO_FIGURE_IN_DOCUMENT means we searched the full text and there is no percentage in it at all. That last one exists because of MG.

A script in the repository enforces the rule the dataset stands on: any value that is not an explicit absence must reference a source document, and any quoted clause must carry the models it applies to. It runs on every change. That second check is what stops "five of Tata's seven owner manuals" becoming "Tata" the next time somebody edits in a hurry.

Three gaps we would rather state than have pointed out. Tata's smaller packs, the Nexon.ev 30, the Tiago.ev 19.2 and the Punch.ev 35, carry terms we could not find published anywhere. The XPRES-T EV manual's warranty chapter sits past the range we could read. And the Mahindra XUV400 has no downloadable warranty guide at all; its manual exists inside a JavaScript portal with no citable link. All three are in the dataset as absences with the reason attached.

If you work for one of the manufacturers listed and we have a cell wrong, that is the most useful message this project can receive. Open an issue with a link to the document, or write to hello@voltu.energy and we will file it for you. We will correct it in public, with the date, crediting whoever caught it, exactly as we correct our own.