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Episode 179 · Deep tech · 60 min

Sell electrons, not batteries

Exponent Energy charges an auto or a bus in 15 minutes. At its Bengaluru factory, Arun Vinayak and TDK Ventures’ Nicolas Sauvage explain why the money is in the charging and why the company started with autos when it wanted buses.

Mobility & EVDeep tech & hardwareVenture capital
AV
NS
Arun Vinayak and Nicolas Sauvage
Exponent Energy · TDK Ventures · with Vishal Krishna and Shreyas Mishra
Sell electrons, not batteries: episode thumbnail
59:56
The brief

The argument in sixty seconds

Exponent Energy sells electrons, Arun Vinayak says, and the battery is how it gets to sell them: each dollar of battery on the road brings three to four dollars of charging. So the market is commercial vehicles, by his count 10% of India’s vehicles but 70% of the energy they use. Exponent never changes the cell. It manages each one more closely and claims 3,000 tested cycles, where slow-charged fleets get 1,000 to 2,000. The factory automated its quality checks before its processes. Retrofits, sold as an energy service, open a parked fleet 10 to 15 times the size of new sales. Nicolas Sauvage of TDK Ventures says Indian investors, used to four-year returns from SaaS and fintech, must recalibrate for deep tech.

Disclosure: TDK Ventures, which Nicolas Sauvage leads, is an investor in Exponent Energy. It joined Exponent’s $26.4 million Series B, led by Eight Roads Ventures, in December 2023, and co-led a ₹200 crore round with 360 ONE Asset in June 2026.

The business, drawn

Eleven charts, sixty minutes

Figures are as said on air unless marked; derived figures say so. Company dates come from Exponent’s announcements, reported by Autocar Pro, EMobility+ and EVreporter. Click ▶ to hear them.

Follow the electrons to commercial vehicles

where the energy goes, and where Exponent’s money comes from · as said on air
Who uses the energy
commercial vehicles: share of all vehicles10%share of the energy they use70%Exponent’s figure, also cited in EP 109
Per $1 of battery
the battery Exponent deploys$1the charging it then sells$3–4“our business is charging”
A battery supplier would chase two-wheelers, the biggest market for batteries, Arun says, but an energy company goes where the electrons are used. Two-wheelers and cars charge at home; commercial vehicles run 200 to 300 km a day across the city, and buses 600 km.▶ 1:34▶ 4:48▶ 5:06

Wanted buses, started with autos

the order Exponent took its battles in · dates from company announcements, reasons as said on air
Wanted first
Buses
15-minute bus charging, “a unicorn of charging”
▶ 6:34
2020
Three-wheelers
“a less cool product”, but it needed less capital
▶ 7:03
Nov 2025
Exponent Oto
retrofits for CNG and LPG autos
▶ 44:41
Jan 2026
Fresh Bus
up to 250 intercity e-buses on Exponent charging
Oct 2026
Buses at the factory
the conversation was recorded behind one
▶ 1:04
Three-wheelers let Exponent prove its technology first, Arun says. India made that easier, Nicolas adds: none of its 70-plus auto makers had a 100-person BMS team, so they would work with a startup, whereas pitching BMW or General Motors would be “challenging”.

In India, value comes from removing friction

frictions named on air, and Exponent’s answer to each
the frictionExponent’s answercharging takestoo longa 15-minutechargethe vehicle’s resalevalue is a worryits ownfinancing platformdrivers don’t putthe gun backa gun thatcomes back
Arun works backwards from the customer to every friction point; companies abroad, he says, grow by adding better features. Nicolas defends jugaad as a discipline: learn on kit 10 to 100 times cheaper, then buy the best equipment once the design is right.▶ 14:35▶ 15:05▶ 19:36

The value sits between wall and cell

how an electron gets from the grid into a vehicle, as Arun lays it out
Gridthe same electron for alle^pump chargerbuilt with the batteryConnector“still very unhappy” with itBMS and algorithmsa bus pack has 600 cellsThermal managementfaster means hotterCelleveryone has it within ~18 monthsdashed: open to every companyfilled: where Exponent builds
What Exponent has built is “still like 1%” of what it wants to build, Arun says, and the connector is what customers will accept for now. Charging faster makes heat, as faster computing does in data centres.▶ 37:48▶ 38:12▶ 38:33

TDK added financing, a network and materials science

TDK Ventures and Exponent, as both describe it
Financing
Exponent One
Arun first talked the financing platform through with TDK Ventures’ Ravi Jain
Patterns
100X
a private two-day event each year for the portfolio, TDK staff and 150+ investors
Materials
A moonshot in Japan
a joint project with a TDK materials-science team
The bar
A global fund
no India fund and no lower standard; India is its no. 2 country by number of deals, Nicolas says
A corporate VC should complement the founder’s strengths and can help its parent too, Nicolas says. If the Japan moonshot works, it “truly moves the needle” for Exponent and shows TDK’s own scientists something they did not think possible.▶ 23:00▶ 26:40▶ 34:35

Fast charging, yet more cycles from the cell

charge–discharge cycles · as said on air
a cell’s inherent life5,000what the field gets, charging slowly1,000–2,000Exponent, charging in 15 minutes3,000 tested01k2k3k4k5kcharge–discharge cycles
Charger, battery and vehicle usually come from three companies, Arun says, so one fixed profile treats every cell alike for years. The industry charges slowly to cut failures, but that is still “driving blind in the night”.▶ 31:13▶ 31:54▶ 32:12

The test rig ages a battery 4–5× faster

time to log 3,000 cycles · derived from the cycle rates given on the factory tour
on the road: 2–3 cycles a day1,000–1,500 dayson the rig: 10–12 cycles a day250–300 daysthe aim, with a digital twin“a few days”05001,0001,500days to log 3,000 cycles (derived)
Exponent tests each new algorithm for ten to twelve months before it will promise 3,000 cycles. With a digital twin and TDK’s materials scientists, Arun aims to cut that learning curve to a few days.▶ 35:43▶ 36:12▶ 58:27

Automate the checks first, the line last

the order in which Exponent automated its battery line · as said on air
Start
A garage line
fully manual
▶ 41:02
Measure
End-of-line testers
built by the design engineers; month one rejected 40% of batteries
▶ 41:13
Learn
99% pass-through
by working out which parameters matter and letting the rest go
▶ 41:20
Automate
Machining and processes
moving material between stations is still manual
▶ 41:33
Next
Cell in, battery out
one straight, fully automated line
▶ 57:55
Most firms automate material handling first, Arun says, and end up with a line too constrained to work, too costly or too slow. His line “looked very bad” two years ago, but customers need not know, Vishal says, “as long as you solve the pain”.

The parked fleet is the bigger market

the retrofit case, as said on air, with Arun’s June 2026 figures
The market
new vehicles sold1×vehicles already on the road10–15×retrofit cost vs a new vehicle40%said on air~49%₹1.7 vs ₹3.5 lakhsecond bar: Arun’s figures, June 2026
The model
dieselLPGCNGelectricevery switch came through retrofitssold as energy as a serviceno upfront payment by the drivera monthly bill below his fuel spendkeeps his usual garage for brakes and tyresno old vehicle to junk, no new one to finance
Every past fuel switch went through retrofits, Arun says, because vehicle makers hedge across technologies. Waiting on them means five years, which an energy company “can’t survive”, Nicolas adds. Exponent says it retrofitted 200 autos in a four-month Bengaluru pilot. Nicolas wants retrofits allowed nationwide.▶ 44:41▶ 45:28▶ 46:08▶ 46:24

600 amps change how you weld

the laser welder Exponent built in-house, from the factory tour
600 A through one batterya busbar thicker than the world averageso a higher-power laserwhich leaves blowholes and heats cellsfix: camera for X–Y, plasma for Z1,200 to over 1,500 welds per bus,each at the right focal length
Getting every weld right is “the foundation”, Arun says. Japanese engines owed their reliability to bore-to-bore tolerances more than design, he argues, and a battery that “dies” has usually lost a few cells to tolerances that were wrong.▶ 39:22▶ 56:16▶ 57:17

Four-year money meets ten-year companies

years to an outcome · as said on air, except C2i (public record)
what Indian investors expect, after SaaS~4deep tech, Nicolas’s anchor10Groq’s “overnight success”10an Indian marketplace10–15C2i, founding to sale (record)~205 yrs10 yrs15 yrs
Investors need patience, meaning purpose, and impatience, meaning urgency, Nicolas says. TDK expected C2i to take a long time, so its quick sale to Infineon was the exception. Selling Exponent now would bring a very good return, he says, but not an exceptional one.▶ 50:13▶ 50:26▶ 51:11
Worth keeping

Lines that stay

In deep tech, overnight success takes 10 years.

Nicolas Sauvage, on patient capital ▶ 50:26

You can only pick a few battles. Be flexible on everything else.

Arun Vinayak, on starting with three-wheelers ▶ 7:20
Chapters

Where the conversation travels

Every block is a chapter, coloured by what it's about. Click any of it to jump straight to that minute on YouTube.

0:00–1:13 · Introduction021:13–4:23 · Why commercial vehicles034:23–14:04 · Choosing customers and the energy business0414:04–22:56 · Design thinking and jugaad0522:56–30:46 · Investor support and financing0630:46–40:02 · Fast charging and battery life0740:02–44:07 · Automating quality first0844:07–49:22 · Retrofitting vehicles0949:22–54:59 · Patient capital and urgency54:59–55:40 · Factory tour1155:40–58:13 · Quality checks and laser welding1258:13–59:56 · Battery cycling and reliability10:0020:0030:0040:0050:0059:56
Mobility & EVProduct strategyVenture capitalDeep tech & hardwareManufacturing
01Introduction 0:00 02Why commercial vehicles 1:13 03Choosing customers and the energy business 4:23 04Design thinking and jugaad 14:04 05Investor support and financing 22:56 06Fast charging and battery life 30:46 07Automating quality first 40:02 08Retrofitting vehicles 44:07 09Patient capital and urgency 49:22 10Factory tour 54:59 11Quality checks and laser welding 55:40 12Battery cycling and reliability 58:13
Glossary

The jargon, unpacked

Battery management system (BMS)
The electronics and software that monitor each cell in a pack and decide how much current it can safely take.
CC-CV charging
Constant current, constant voltage, the standard charging profile: the charger supplies full current until the cell reaches a set voltage, then holds that voltage while the current tapers.
Cycle life
How many full charge and discharge cycles a battery gives before it holds less than a set share of its original capacity, often 70 to 80%.
Busbar
A thick metal strip that joins the cells in a pack and carries their current. More current needs a thicker bar.
Digital twin
A software model of a physical system, kept in step with test data, so experiments can run in simulation before they run on hardware.
Corporate venture capital (CVC)
A venture fund owned by a large company. It invests the parent’s money for financial returns and for what the parent can learn.
Connections

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Mobility & EVDeep tech & hardware
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EP 102 · Deep tech

The technologies that friction sets free

Nicolas Sauvage on TDK Ventures’ thesis and why friction helps challengers
Venture capitalDeep tech & hardware
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EP 114 · Deep tech

Capital is the easy part

TDK Ventures’ Anil Achyuta on the backers a hardware startup needs
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Full transcript

The whole conversation, searchable

176 segments
AVArun Vinayak, Exponent EnergyNSNicolas Sauvage, TDK VenturesVKVishal Krishna, UpStreamVoiceSMShreyas Mishra, UpStreamVoice

The published video’s corrected captions, attributed to speakers from context; brief interjections such as “Absolutely.” are left out. Click a timestamp to open that moment on YouTube.

Checked against the record: India produces about an eighth of the crude it uses (import dependence was 88.2% in FY25, per PPAC), and its crude import bill that year was about $137 billion (said: “India has zero petroleum”, “a $150 billion bill every year”). We found no public source that splits the bill by vehicle type, so the $100 billion said for commercial vehicles could not be checked. Nvidia did not buy Groq: in December 2025 it took a non-exclusive licence to Groq’s inference technology, reported at about $20 billion, and hired its founder and president; Groq continues as a company (said: “Groq too, which got sold to Nvidia”). Arun told Business Today in June 2026 that a retrofit costs about ₹1.7 lakh against about ₹3.5 lakh for a new vehicle, nearer half than the 40% said on air. The 10% of vehicles and 70% of energy split is Exponent’s own figure; TERI puts commercial vehicles at 64% of retail diesel.