Battery and Motor is main drive train in a EV just as Engine and Gearbox is in ICE auto. It is insider knowledge in Automotive circles that Chinese are far ahead of everybody in Battery and Motor tech in both Cost and Performance. Tesla match them only in performance.
In electronic and Power components such as BMS, VCU, DC-DC etc it is difficult to beat them. Cost per soldering point in China is typically about 10 paise. The same in India used to be Rs.1 or more, it has now coming down to about 50 paise or less here after Foxconn and others setup captive lines. Even for related mechanical parts like Shields, cost of raw material here is more than produced component cost there. Sourcing a casting for lower power DC-DC costs 120 bucks locally. Entire DC-DC unit including all power components is available from just 150 i.e less then 2$ there (though thermal performance may not good). A leading Microprocessor supplier evaluated building their SOC based module in millions per year here couple of years ago. The cost was coming to 7$+. The same was available in China for little more than 1.5$
But Europe, US & India don`t allow Chinese components directly. To get around this, Chinese together with many companies, particularly German ones have figured out a way where they extensively use local Chinese parts in their products to match performance and cost. For example, I could send specs of 3M Tapes, Bollhoff Helicoils, Wruth Capacitors to any of my Chinese supplier and they will identify and provide Chinese equivalent Brand and Part Number. Where my MNC client would previosuly use the original parts in the production line, they now readily use Chinese equivalent. To be fair, these Chinese parts will pass German QC tests without a single issue.
Many automotive suppliers, including biggest names like *osc* tried doing the same for batteries. But Chinese have so far flat-out refused to allow white labelling in large volumes for the leading edge batteries. It is allowed in smaller scale like Drone batteries etc. So if I need batteries for EV line, options are either buy cells from Teir-2 suppliers with slightly older technology and assemble battery under own brand or of if current Tech is wanted, sign-up to buy directly from biggies like BYD under their brand.
Putting it in simpler terms, If Chinese cars are allowed to be sold directly in India today, Indian brands will practically disappear. Tatas and Mahindras don`t have capacity or knowhow to build equivalent Motors or Batteries on their own EVEN IF THEY WANTED TO.