The new Renault ZOE Z.E. 40 proves that it's possible to double battery capacity, without redesigning an entire car.
The key is to originally develop a battery pack that could handle future modules with more energy dense cells (see video below).
In the case of ZOE Z.E. 40, available energy went up from about 22 kWh to 41 kWh, while the dimensions of the battery remained unchanged, with the weight increasing by only 15 kg (33 lbs) - from 290 kg to 305 kg (5%).
Physically, Renault still uses a 192 cells (LG Chem) in 12 modules (16 cells per module) configuration.
With 41 kWh of energy in the sub-compact model, a real world range of 300 km (186 miles) is possible (officially in Europe the ZOE is rated at 400 km on the NEDC scale).