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How much battery is “enough”?

David Hudson, Tata Motors European Technical Centre

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Context

• Tata Motors builds cars and trucks primarily for the Indian market• Currently demand in this market is not well-established• Strong commitment from Indian government to adopt electrification

• Energy security• Cost of transportation• Environment, especially urban air quality

• Present electrical infrastructure is notoriously unreliable ….

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India!

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A question…

• Is the trend towards greater range (and hence more kWh) actually the right answer for all markets?

• Consider the compromises:• Cost• Charge time• Weight• Impact on base vehicle packaging

• Perhaps we need to describe capacity and range in qualitative terms?

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The BEV challenge …• Provide plug-in passenger vehicles for a range of private and commercial

users in a market where conventional cars cost around $5000 and where there is little existing charging infrastructure (so far ….)

• No established market to allow conventional volume forecasting and capacity planning for business case ….

• Minimise capital investment• Retain manufacturing flexibility• Carry over as much of the validation of existing vehicles in market as possible• Balance total cost against functionality/attribute performance

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How much range do we really need?

• Easy to follow the herd and make up a nice round number of miles or kilometres …. “200 … 300 … 400”

• User patterns are well known to everyone ….. apart from the users!

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Annual driving distance

There are a very few long distance driversPattern heavily skewed to the low end!

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Average driving distances in India

Daily driving distance

90% of users drive around 100km per day …Why would anyone need a long range EV?

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Indian urban driving average speed

Very modest average speeds in most large cities

Caution!Seasonal and climatic issues mean that hotel loads can be higher than traction consumption!

Real world energy use is NOT well represented by certification test!

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Tiago BEV– Overview

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Tiago BEV– Overview

Charge Socket LocatedWithin Fuel Fill Aperture

Tata e-Drive System withIntegrated Motor & Controller

13kWh refrigerant-cooledLi-ion Battery Pack

Console Mounted Drive Selector

Objective: Develop lowest cost competitive BEV with robust supply potential.

• Range 110km on full charge• Recharge time:

• Indian domestic supply <5 hr• 20kW DC <40 mins

• Maximum speed 130 km/h• 0-100 km/h in 10 seconds• Kerb weight c. 1050 kg

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Effect of a small battery

• It works hard more of the time!• Higher C rate during discharge and charge cycles:

• Potential need for cooling• Needs to have good energy and power characteristics

• Advantages to using cell formats with good heat transfer properties• Choice of Samsung SDI prismatic cells (37Ah) in 8 modules• Active cooling through direct refrigerant circuit with diverter from

cabin AC

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Urban battery pack• Direct replacement for fuel tank in

donor car

Worse

Better

• Competitive energy density with other EVs

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• Fabricated steel case• Direct refrigerant cooling circuit• Base contains structure for module mounting• 120kg including BMS and cooling system

Urban battery pack

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An answer?

• Is the trend towards greater range (and hence more kWh) actually the right answer for all markets?

• Consider the compromises:• Cost• Charge time• Weight• Impact on base vehicle packaging

• Perhaps we need to describe capacity and range in qualitative terms?

#BEstorage

Thanks for your attention!

Questions?