EV owners keep asking if DC fast charging ruins the battery: what makers say

It is the oldest question on the Indian EV forums and it has not been settled: if you live in a flat with no home charging point and plug into a DC fast charger twice a week, are you quietly destroying the battery you paid lakhs for?

What owners are asking, and where

On Team-BHP's electric cars forum, search results show at least three separate threads built around this one question, including one titled "Is it OK to only fast-charge your electric car? No slow charging at all" and another on best practices to home-charge an electric car for longer battery life. Those pages would not open for us, so we are reporting only what the search listings show, with no reply counts or dates of our own.

One thread we did open is on Tesla Motors Club, where an owner asks whether it is bad to supercharge all the time. It started in May 2023 and the first page carries 20 replies running to July 2023. The agreement there is narrow but clear. Supercharging only causes somewhat more degradation than home AC charging, it will not kill a pack on its own, and for most owners the running cost of public DC charging hurts more than the chemistry does. One reply raises lithium plating as a late-life concern past 100,000 miles. No owner in that thread produced an official Tesla document saying DC-only charging is disallowed.

The makers do put it in writing

Kia India's EV6 owner's manual is blunt. It says "Battery performance and durability can deteriorate if the DC charger is used constantly" and "Use of DC charge should be minimized in order to help prolong high voltage battery life."

Mahindra's XEV 9e owner's manual takes a different angle. It asks owners not to leave the vehicle at 100 per cent state of charge for prolonged periods because it "may reduce battery longevity", while also recommending that the vehicle reach a full 100 per cent before you end a charging session. It warns against exposing the vehicle to very high or freezing temperatures for long durations, and it states plainly that battery performance will fall with time and use, and that this is not a defect.

Note what is not there. In the two manuals we read, neither makes AC charging a condition of the battery warranty, and neither sets out the "one AC charge after every four DC charges" rule that owners often quote to each other on forums. If your maker has that in writing, ask for the clause.

What the data says, and what India's heat adds

Geotab published fresh telematics analysis on 13 January 2026 covering more than 22,700 electric vehicles across 21 makes and models. The fleet-wide average capacity loss is 2.3 per cent a year, up from the 1.8 per cent its 2024 work found.

Split by habit, vehicles leaning on DC fast charging above 100 kW lost up to 3.0 per cent a year, against around 1.5 per cent for those mostly charged on AC or low-power DC. Geotab also found that degradation speeds up when a vehicle spends more than 80 per cent of its time sitting at a very high or very low state of charge.

The line that matters most for an Indian owner is the climate one. Hot regions showed roughly 0.4 per cent faster loss per year than mild ones, and the heaviest-used vehicles about 0.8 per cent faster. Electrive, reporting the same study, reckons even a heavy DC user would still be near 78 per cent state of health at eight years, above the 70 per cent most warranties guarantee. That projection is Electrive's own arithmetic, not Geotab's figure.

What an owner can do

Read the charging section of your own manual before you trust a forum. Set the daily charge ceiling in the app, keep AC charging for routine running and DC for highway days, and avoid leaving the car parked at 100 per cent or near empty for days in May heat. Park in shade where you can. At every service, ask the dealer for a written state-of-health readout and keep the printout, because that paper is what a warranty claim turns on later. If a claim is refused despite the pack being below the warranty threshold, escalate to the maker's customer care in writing, then to the National Consumer Helpline on 1915.

Owners, what state of health is your car or scooter showing, and how much of your charging has been DC? Post your odometer reading with it.

Sources

• Geotab: EV Battery Health Study, new data on fast charging and degradation (13 January 2026)
• Electrive: Geotab analysis, measuring the impact fast charging has on the loss of battery capacity
• Kia India EV6 owner's manual, DC charging chapter
• Mahindra XEV 9e owner's manual
• Kia: AC and DC charging, owner guidance
• Tesla Motors Club thread: Is it bad to supercharge all the time?