Fast-Charging EVs In 15 Minutes: How India’s Exponent Energy Is Using Water To Solve A Red-Hot Challenge

High charge times and range anxiety remain barriers to mass adoption of electric vehicles, but the Bengaluru-based start-up promises to make EV charging quicker, affordable and profitable with a fundamentally simple approach.

By Amaan Ahmed


7 mins read


Published on August 2, 2023

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  • Exponent Energy has devised an off-board cooling system to enable rapid-charging of EVs.
  • Refrigerated water is pumped into the battery pack’s cooling channels during charging to keep cell temperatures well below 35 deg C.
  • This solution cuts charge times down to 15 minutes; enhances profitability as a business.

Today, regardless of whether it’s at a social gathering, a family get-together or on an online thread, you’re quite likely to find yourself in the middle of a discussion relating to electric vehicles (EV). Interest levels in cleaner mobility continue to rise, many myths have been dispelled and several barriers to mass adoption have disappeared in the last few years. 


However, key questions still come thick and fast – Is fixed charging feasible for a country with such a vast population? Isn’t range anxiety still a concern? Aren’t EVs too expensive and take too long to charge? One Indian start-up has taken it upon itself to put all these concerns to bed once and for all, devising a solution that is clever, and yet, wonderfully simple.


Also Read: Former Ather Energy Chief Product Officer Launches Exponent Energy


rapid charging electric vehicles in 15 minutes how indias exponent energy is dousing a red hot concern using water carandbike 5

For EVs that incorporate its energy stack, Exponent promises a full charge in just 15 minutes.


Bengaluru-based Exponent Energy came to life in 2020, founded by Sanjay Byalal Jagannath and Arun Vinayak. The latter is also one of the cofounders of one of India’s leading electric two-wheeler manufacturers – Ather Energy. Having led the creation of the 340 and 450 series electric scooters and making a key contribution to the electrification of two-wheelers in the country, Vinayak made an exit from Ather to address a major stumbling block for EVs on the whole – charging.


At present, plugging in an EV comes with its own set of challenges. Slow charging takes several hours, and while fast charging can solve that to a certain extent, it can also have a detrimental impact on battery life. And then there’s the matter of profitability – if an EV charger can only serve two vehicles a day, it won’t generate enough revenue to be viable. Vinayak terms it a ‘two-sided’ problem that exists today because vital components involved in the charging process – the battery, charger and connector – are usually manufactured by different firms, and are not optimised to work together.


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Its first, proprietary battery pack has a capacity of 8.8 kWh (installed) and uses regular LFP cells; installed in a cargo three-wheeler.


Also Read: Electric Three-Wheelers With Rapid 15-Minute Charging, Exponent Energy And Altigreen Announce Partnership


Exponent designed its own battery pack, charging station, charging connector and battery management system (BMS) to overcome these hiccups. For the better part of the last one year, Exponent has made claims about its ability to fully charge an EV from almost zero per cent to 100 per cent in a scarcely believable 15 minutes. More interestingly, it recently announced that its battery pack was tested by German test agency TUV, which reported the battery only suffered 13 per cent degradation after being subjected to 3,000 15-minute rapid-charging cycles. And all this, using regular lithium ferro-phosphate (LFP) cells that are available today.


What’s the magic word? Water.


In its studies, Exponent noted that EV batteries don’t heat up as much when a vehicle is being driven as they do when they are being charged. The heat generated when a battery is fast-charged can be 256 times higher than what is generated during a slow charge, which, once high ambient temperature (exceeding 40 degrees Celsius) is factored in, inevitably stalls the fast-charging process. A standard active cooling system for the battery adds cost, but is not necessarily effective, and using a full-blown heating, ventilation and air-conditioning (HVAC) system in its place is an expensive affair. Installing one can cost as much as Rs 1 lakh on a two-wheeler, Rs 2.50 lakh on a car and Rs 10 lakh on a large truck, substantially impacting their pricing. There’s also the matter of weight – an HVAC system can add anywhere between 25 kg to 300 kg to the vehicle’s weight, depending on whether it’s a scooter or a truck.


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The e-pump houses the HVAC system and a 30-litre water storage tank. 


Instead, Exponent has incorporated the HVAC system into its 45 kW ‘e-pump’ rapid charger, as well as an in-built liquid cooling system into its proprietary charging connector. Each e-pump can hold up to 30 litres of water stored at 10 degrees Celsius, which is delivered to the twin-sided cooling channels built into the battery pack via the heavy connector, which weighs about 8 kg and delivers 600 amps of current. Doing so ensures cell temperatures are quickly brought down to somewhere between 25 to 35 degrees Celsius, regardless of how high the ambient temperature is.




Exponent’s BMS leverages real-time cloud data to read the state of every cell in a pack, and accordingly constructs a custom charging profile for each battery, to prevent lithium-plating that results in battery health deterioration. The result is that EVs using Exponent’s energy stack can rapid-charge in 15 minutes, over and over again, thousands of times. This is crucial in the commercial-use sector, where minimal downtimes spell higher earnings.


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Twin-sided channels are supplied with refrigerated water (cooled to 10 deg C) during charging to keep cell temperatures below 35 deg C.


In a way, Exponent is aiming to take battery-swapping out of the equation, which Vinayak believes is hard to scale for different vehicle types, requires too many surplus batteries and necessitates battery standardisation, which vehicle manufacturers would be averse to.


“OEMs are happy to buy technology, but they want to control the specifications, which turns them off swapping. Battery swapping is also expensive – for every 100 vehicles, you need 150 to 200 batteries in the network. If you want good performance, economics and durability, you need a deeply integrated product. To remove the battery is actually a step backward in evolution”, Vinayak tells carandbike.


This arrangement also provides greater incentive from a business point of view, as each charger can serve multiple vehicles in a single day. Exponent says one of its over 30 chargers already operational across Bengaluru once recorded 41 sessions in a single day, meaning the charger was in use for a little over 10 hours. The vehicles charged at the e-pump were three-wheelers with a battery capacity of over 8 kWh. At present, Exponent levies a fee of Rs 14-16 per unit of electricity consumed, which totals up to an average spend of Rs 120 per vehicle.


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Exponent will explore making its charging connector open-source in the future.


By removing the costs and complexities of battery cooling from the vehicle, the start-up promises to make vehicles more affordable. By speeding up the charging process, it brings a new dimension of convenience to the end user, and a never-seen-before level of profitability for a business owner. And Exponent says it can custom-build an energy solution for any vehicle manufacturer open to collaborating, regardless of the type of cell or cell chemistry chosen. However, its immediate focus is on the commercial sector (cargo three-wheelers for delivery fleets and heavy-duty trucks/buses) where energy consumption is comparatively higher and rapid-charging is a need, more than a want.


Over the next two years, Exponent plans to deploy around 1,000 e-pumps across Bengaluru, Delhi-NCR, Mumbai, Chennai, Ahmedabad and Hyderabad via a franchise model. While these are likely to serve only delivery vehicles and long-haul trucks and buses in the initial years, Exponent’s effective-yet-straightforward approach can easily adapt to serve private-use two- and four-wheelers in the future. While it remains to be seen if vehicle manufacturers are receptive to incorporating Exponent’s full-fledged energy stack into their ecosystems, as a solution that addresses most concerns relating to EV charging, this could be a pivotal moment in India’s electrification story.


Last Updated on August 2, 2023

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