Tata Motors switches to pure EV architecture with Punch EV

Four years into the launch of its ICE-derived Nexon EV, Tata Motors has switched to its Gen-2 EV architecture, christened ‘Acti.ev’, with the all-new Punch EV, launched on January 17. The company says despite the Punch EV bearing a similar ‘top hat’ as its internal-combustion engine (ICE) counterpart, a lot has changed underneath, in terms of the platform, enabling the all-electric Punch to offer authentic EV credentials.

To do this, the company has significantly altered the monocoque of the Punch, making critical changes to the car’s floor pan, particularly eliminating the hump in the rear section, that houses the catalytic convertor as well as the exhaust pre-treatment system in the ICE version. This aspect enabled engineers to offer a fully-flat floor — a typical EV trait, thereby liberating more space in the rear half of the cabin.

The move also allowed to lift the orthogonal battery pack, integrated underneath the floor of the Punch EV, and offer a 3mm higher ground clearance — pegged at 190mm — than the petrol-powered Punch. With the integration of the battery pack, there is no impact on the boot capacity whatsoever, which remains identical to the ICE Punch at 366 litres.

ICE and electric versions of the recently refreshed Punch may have a similar silhoutte, but that's where the similarities end. Underneath the EV, there's a massively reworked platform that is specific to the model's powertrain packaging specifications. 

These critical changes intensify the company’s efforts into building the Punch EV beyond a mere ICE-to-EV conversion, also classifying the Acti.ev as a pure-EV platform. According to Anand Kulkarni, Chief Product Officer, and Head, HV Programs and Customer Service, Tata Passenger Electric Mobility (TPEM), “The Punch EV is completely different from the internal-combustion engine version as the Acti.ev architecture is designed, optimised, and developed to cater to pure-EV models.”

“There are significant changes between the two cars in terms of the floor layout, sill layout, as well as crash-load paths to allow for the creation of additional capabilities to support multiple drivetrain configurations — front-wheel, rear-wheel, and all-wheel drive — on the Acti.ev platform. This has led to several changes in the layout of the architecture itself.” The upcoming Tata Curvv and Harrier EV will be based on the Acti.ev architecture as well.

Kulkarni further explained that because of the higher mass of EVs over ICE, it was imperative to manage the side-crash impulse on the Punch EV, and Tata Motors' engineers have achieved that by leveraging material technology. The company has reinforced the door sills on the sides with ultra-high-strength steel (UHSS) that offers more torsional rigidity. This has enabled the company to achieve 30 percent higher torsional stiffness on the Punch EV’s monocoque, which is up to 15 percent lighter than its ICE counterpart. Tata Motors is confident that the Punch EV is ready to meet the stringent five-star safety requirements in the Bharat NCAP crash tests, and the heavily modified platform has also led to a reduction in the number of tools on the assembly line.

The company says there are 40 less tools required to make the Punch EV monocoque than the ICE platform. However, to assemble both cars on the same line, a change has been induced in the manufacturing process. Tata Motors has created a ‘forking’ on the assembly line to seamlessly switch between the ICE and EV monocoques on the main conveyor for final assembly. “There are lesser parts in the architecture, and the manufacturing processes have changed as well. Therefore, all put together, it is an extremely comprehensive change under the floor, and while there may be some dimensional similarities between the ICE and EV versions, the platforms are completely different,” Kulkarni said.

LFP battery chemistry

The Punch EV deploys an orthogonal-shaped battery pack that houses lithium-iron-phosphate (LFP) chemistry cells which are cylindrical in shape. As per Kulkarni, “The battery pack has been laid underneath the floor, and by deploying an orthogonal shape for the pack, we have been able to improve the packaging efficiency by 10 percent, thereby being able to offer good energy storage in this footprint.” The Punch EV comes with two battery pack options — standard 25kWh unit with a claimed range of 315km, and the long-range version with a bigger 35kWh pack offering a Modified Indian Driving Cycle (MIDC) range of 421km.

“The Acti.ev architecture is chemistry agnostic, and therefore, it is possible for us to use different battery chemistries on this architecture, depending on the requirements of other models on this platform in future,” Kulkarni added. With four levels of regenerative braking, Tata Motors says the maximum regen on the Punch EV can vary between 0.15G to 0.19G, thereby allowing to regenerate a significant amount of energy into the battery pack. In terms of charging, the Punch EV comes with a 3.3kW AC wall-box charger as standard that could recharge the 25kW battery pack in 13.5 hours. The option of a 7.2kW AC fast charger with the long-range version, which gets recharged in 5 hours is available and both versions can accept up to 50kW DC fast charging, thereby going from 10 to 80 percent in less than an hour.

First drive impressions

The Punch EV boasts 50:50 weight distribution between the front and rear enabling engaging dynamics, particularly in terms of the car’s handling and stability around fast corners. And despite being high off the ground, the body roll is well contained despite it having a comfortable and softer suspension setup. With its 16-inch wheels, the EV absorbs bumps and potholes with aplomb. To achieve an identical static ride height despite its up to 250kg higher kerb weight than the regular Punch, Tata Motors has stiffened the suspension springs on the Punch EV.

This feature was first published in Autocar Professional's February 1, 2024 issue.