The Battery Spec Sheet India Deserves — and No One Publishes

We verified it on this site this week: the official, downloadable spec sheet of one of India's most respected EV makers contains exactly two battery lines — an energy figure in kWh and a warranty. No voltage. No ampere-hours. No charging current. No cutoff voltages. And that maker is one of the better ones. This is the state of battery "specifications" in India in 2026.

So instead of only criticising, this page does something more useful: it publishes the complete spec sheet every battery sold in India should carry — for EV scooters, home inverters, solar storage, all of it — explained line by line, with the reasons each number protects the buyer.

1. Identity: Voltage and Ah, Not Just kWh

"3.7 kWh" tells you energy, not architecture. The real identity is the nominal voltage (set by chemistry and cell count — e.g., a 14s NMC pack ≈ 50.4 V; a 16s LFP pack = 51.2 V) and the capacity in Ah (3.7 kWh ÷ ~51 V ≈ 72 Ah). Without V and Ah you cannot match a charger, size a replacement, or compare two packs honestly. Every brochure should state: chemistry, cell configuration (e.g., 14s4p), nominal voltage, Ah, and gross vs usable Wh.

2. The BMS Section — the Specs That Prevent Disasters

The Battery Management System is the battery's bodyguard, and its settings decide both safety and life. These four numbers must be published, because without them a buyer cannot know if a charger is safe for the pack:

BMS spec	What it is	Why the buyer needs it
High-voltage cutoff (charge)	The pack voltage at which charging must stop (e.g., 4.2 V/cell NMC, 3.65 V/cell LFP)	A charger exceeding this overcharges the pack — the classic cause of swelling and fire
Low-voltage cutoff (discharge)	The voltage at which the BMS disconnects the load	Protects against deep discharge, the silent killer of lithium life
Maximum charge current	The highest current at which the pack may be charged — and whether the BMS enforces a charge-current cutoff	Defines which chargers are safe; fast-charging beyond it cooks the cells
Charger rated output	The supplied charger's voltage profile and output current	So a replacement charger can be matched exactly — wrong chargers destroy more batteries than age does

How deep this really goes

A professional-grade BMS datasheet goes far deeper than these four numbers — alarm, protection and recovery thresholds each with time delays, at both cell and pack level, balancing parameters, separate temperature limits, even the BMS's own self-consumption current. That depth deserves its own dedicated article, which this site will publish as part of the spec-transparency series. For this manifesto, the four numbers above are the floor every buyer should demand.

Every assembled battery in India sits on a BMS that has this entire table defined inside it. The manufacturer holds the document. The buyer gets "long life." That gap is the whole problem.

And one more fact that removes every excuse: a BMS is a BMS. Whether it sits inside a 12.8 V inverter retrofit, a 51 V scooter pack, a 350 V car battery or a solar wall unit, the parameter list is identical — over-charge, over-discharge, over-current, temperature, balancing, cutoffs. Only the values change with voltage class and current rating. That means one disclosure standard fits every battery sold in India, across every segment. No manufacturer in any category can claim their product is a special case that cannot be specified.

3. State of Charge Must Be Defined by Voltage

Every scooter and inverter shows a percentage. But a percentage is a software estimate; voltage is physics. If "80% charged" is defined by a published pack voltage, any user can verify it — with the dashboard readout or a ₹300 multimeter — and catch a battery meter that's drifting as the pack ages. The spec sheet should carry a simple table, like this illustration for a 16s LFP pack:

State of charge	Pack voltage (16s LFP, illustrative)	Per-cell
100% (charge cutoff)	58.4 V	3.65 V
~80%	~53.8 V	~3.36 V
~50%	~52.5 V	~3.28 V
~20%	~51.2 V	~3.20 V
0% (discharge cutoff)	~44.8–48 V	2.8–3.0 V

Illustrative values for the format; the exact table must come from each manufacturer for its own pack and chemistry. The point is the format: SoC anchored to voltage, published.

4. Ageing Must Be Measurable: Resistance and Backup-at-Load

A battery's decline should not be a mystery the service centre interprets for you. Two published baselines make ageing measurable by anyone:

Internal resistance — the health meter

Publish the pack's internal resistance when new, at full charge and at low charge. Resistance rises as a battery ages; comparing today's reading against the published baseline tells you — in one number — how much life is gone. Capacity at stated charge levels serves the same purpose.

Backup-at-load — the test anyone can run

Even simpler: the manufacturer states, for a new battery, "at 1000 W this pack delivers X minutes; at 2000 W, Y minutes." The owner runs the same test once a year. If the 1000 W backup has fallen from 60 minutes to 45, the battery has lost 25% — no app, no service centre, no argument. This single line on a spec sheet would end most warranty disputes before they start.

The Model Spec Sheet — Demand This Format

Here is the complete template. Every line is measurable on standard equipment. Print it, hand it to any seller, and ask them to fill it in:

#	Specification	Example format
1	Chemistry & cell configuration	LFP, 16s2p / NMC, 14s4p
2	Nominal voltage	51.2 V
3	Capacity	72 Ah (gross) / 65 Ah usable
4	Energy	3.7 kWh gross / 3.3 kWh usable
5	High-voltage cutoff (charge)	58.4 V (3.65 V/cell)
6	Low-voltage cutoff (discharge)	44.8 V (2.8 V/cell)
7	Max charge current / charger output	20 A max · charger: 54.6 V, 10 A
8	Max continuous / peak discharge	60 A continuous / 120 A 10 s
9	SoC–voltage table	100/80/50/20/0% with pack voltages
10	Internal resistance (new)	X mΩ @ full · Y mΩ @ 20%
11	Backup at stated loads (new)	1000 W → X min · 2000 W → Y min
12	Cycle life, with conditions	3000 cycles @ 80% DoD to 80% capacity
13	Operating temperature & derating	−10 to 55°C; derate above 45°C
14	Cell maker, grade & origin	A-grade, [maker], [country]
15	Warranty: free vs pro-rata + SoH floor	36 mo free + 24 pro-rata; replace <70% SoH

Proof It Can Be Done — A Real Spec Sheet, Filled In

Is this template a fantasy? No. Here is an actual technical specification document for a 12.8 V / 100 Ah LFP retrofit inverter battery sold in India today (Su-vastika, doc. TS/BMS/BT12 — transparency: the author mentors Su-vastika; this sheet is shown as evidence of format, not as a product endorsement):

Parameter	Specified value	Template line it fills
Battery type	LiFePO4	#1 Chemistry
Rated capacity	100 Ah	#3 Ah ✓
Energy	1280 Wh (= 12.8 V × 100 Ah — the identity, demonstrated)	#2, #4 ✓
Charge method	CC-CV	#7 ✓
Charging current	Max 25 A	#7 Max charge current ✓
Discharging current	Max 100 A	#8 Max discharge ✓
Max charging voltage	14.0 V ± 0.1 V	#5 HV cutoff ✓
Battery low cut	11.0 V ± 0.1 V	#6 LV cutoff ✓
Protections	LV cut, HV cut, overload, short circuit, over-temperature	BMS protections ✓
Over-temp cutoffs	Charge >60 °C · discharge >65 °C · working 0–50 °C	#13 ✓
Cycle life, with conditions	≥3500 cycles @ 1C, 80% DoD, to 70% EoL, 25 °C	#12 — the honest format ✓
Efficiency	≥95% @ 50 °C · ≥75% @ 0 °C	Efficiency ✓
Backup at stated load	400 W bulb load → 3 hours	#11 — the degradation self-test ✓
Recharge time	4 h 30 m at 20 A	Charging ✓

Thirteen of the fifteen template lines, on one page, from one Indian factory. The two it could still add — the SoC-voltage table and internal resistance baselines — I will say openly should be added too; the standard applies to everyone, including companies I mentor. But the point is made: every number in the template exists in every factory. Publishing them is a choice. If a retrofit inverter battery can carry this sheet, a ₹1.5-lakh electric scooter has no excuse.

Where Is the Regulator?

India mandates safety testing — AIS-156 for EV packs, BIS standards for lithium cells — and that is good. But safety certification is not disclosure. A refrigerator must carry a BEE star label; a packet of biscuits must declare its contents; a battery costing ₹50,000 to ₹8 lakh is sold on a single kWh number. In my view this opacity shortchanges every Indian buyer, and the fix is simple: a mandatory standard battery label — the fifteen lines above — on every battery sold in this country. The manufacturers already have every one of these numbers; they test them in the factory. They are simply not required to print them.

The Bottom Line

Demand the fifteen lines. A manufacturer who fills the template in writing is selling you a battery; one who won't is selling you a number on a sticker. Until our regulators mandate a standard battery label, this page is that label — use it.

Frequently Asked Questions

What should a complete battery spec sheet contain?

Voltage and Ah, chemistry and cell configuration, BMS high/low-voltage cutoffs, max charge current and charger output, max discharge current, an SoC-voltage table, internal resistance when new, backup at stated loads, cycle life with conditions, temperature range, cell grade and the warranty's free/pro-rata split with SoH floor.

Why do BMS cutoffs matter to me?

They define what charger is safe for your pack. Unpublished cutoffs are how wrong chargers destroy batteries — and how those failures get blamed on you.

Why define charge by voltage?

Percentages are software guesses; voltage is measurable physics. A published SoC-voltage table lets anyone verify the meter.

How do I measure my battery's ageing?

Against published baselines: internal resistance vs the new-battery value, or the backup-at-load test — re-run "X minutes at 1000 W" yearly and read the decline directly.

Doesn't BIS already cover this?

BIS and AIS standards cover safety testing, not consumer disclosure. There is no mandated spec label for batteries in India today.

This is an opinion and analysis piece on specification disclosure practices across the battery industry; it does not allege illegality by any specific company. Illustrative voltages are format examples, not brand data.