Nissan Leaf: A comprehensive review of the Battery pack(Gen1 -Gen5)

 The Nissan Leaf has been one of the highest selling Electric Vehicle in the market. The vehicle topped the North American sales charts during its early years and is still one of the highest selling Electric Vehicle in the EU and UK markets. 

Leaf Gen2(Left) Leaf Gen1(Right)

The USPs of the Nissan Leaf has been one of the key factors for its sales. The competitive pricing and the unadulterated user interface is what attracted buyers. The launch of the vehicle itself was at such a juncture in time, where the world was just restarting from the worst financial crisis and the world was open to something new, yet not highly sophisticated or over engineering. Nissan's hatchback sized pricing and styling allowed many consumers to buy the car as a second car or as a car for many first time buyers. 

Moving to the technical aspects, the Leaf was one of the first mass produced Electric Vehicles long before the Tesla craze had caught up. Currently running on the the Gen 5 Battery Pack and Get 2 body style, the Leaf is manufactured in Japan , USA and the UK by Nissan and in China by Dongfeng Nissan group as the Venucia E30. 

The Generations:

The test cars used for the prototyping and homologation of the Leaf had all been built on the Nissan B platform or the Dacia B0 platform, hence the testing and design phase of the vehicle suggested that the vehicle was a hatchback and the platform would be a derivative of the B platform. 

The launch of the first generation in 2010 saw the vehicle become a top pick by the NHTSA and Euro NCAP, gaining 5 stars in overall passenger safety. A major factor for the vehicle to achieve high safety ratings is due to the structural rigidity and the support provided by the battery pack being located on the floor of the vehicle. Two battery size options were available, the 24kW(2010-2012) and the 40kW(2013-present).  The 24kW pack was replaced by a larger 30kW pack from 2013.

The second gen Leaf was launched in 2018 with revised styling and better ergonomics. The second gen Leaf also features a larger battery pack on the E+ variant raising the pack size to 62kW. The lower variants of the Leaf are now offered with a 40kW battery pack. 

The Battery:

Since the inception of the Leaf, there have been five generations of the battery pack. The robust design of the battery pack has lead to a number of companies using the battery pack in a number of areas such as Energy storage for off grid applications and vehicle conversion applications. 

Gen1 - Gen5 40kWh pack(Left) Gen5 62kWh pack(Right)

Gen 1- Gen 4 Battery Pack

The Gen1-Gen4 battery pack has a rated voltage of 307 volts when not charged and 403.2 volts when fully charged. This is the calculated voltage from the 48 modules connected in series with one another.  Each module of the Gen1-Gen4 battery packs has 4.2V when fully charged and about 3.2V when not charged. From a cell level perspective, there exist 192 cells each rated to a Vmax of 2.1V and a Vmin of 1.6V each. 

Structure of Nissan Leaf Battery Pack

The Gen1-Gen4 battery packs consist of 48 modules, the initial variant which had the 24kW pack had a different chemical composition as compared to the Gen2-Gen4 packs. The 24kW packs were made of Lithium-ion Manganese Oxide (LMO) and had a cell capacity of 32.5Ah paper cell while the 30kW and 40kW packs were made of Lithium-ion Nickel Manganese Cobalt (Li-NMC) and had a cell capacity of 48.2Ah and 56.3Ah per cell for the respective battery power ratings.

Module Comparison

Each module consists of 4 cells, 2 pairs of parallel connected cells connected to each other in series. Each pair of cells has a rated voltage of 4.2V when fully charged and 3.2V when not. Therefore, every module has a minimum voltage of 6.4V and a maximum voltage of 8.4V. 

Battery Components

The modules are connected in three different phases, Module 1 to Module 24 are connected in series at the rear of the battery pack(Rear Module Stack), which accounts for a combined Vmax of 201.6V and a Vmin of 153.6V making it the largest single battery stack in the vehicle, the remaining 24 modules are stacked in a step-shaped pattern,  positioned opposite to each other in stacks of 12 modules making the RH Front Module Stack and the LH Front Module Stack. All the modules are connected in series. Each 12 module stack accounts for a Vmax of 100.8V and Vmin of 76.8V each. Therefore, the total pack consists of 48 modules, with stack 1 consisting 24 modules, providing 201.6V and stack 2 and 3 consisting 12 modules each,  providing a combined output of 201.6V.

Lithium Battery Controller (on the side of the 24th module)

On to one side of the 24th module, the Lithium Battery Controller aka the Battery Management System is placed and it is directly connected to the HV junction box. Those vehicles equipped with a Cold weather package came with an inbuilt battery heater which take direct supply from the Li modules and is connected to the HV Junction box and the service disconnect plug.

This combination applies to all the battery packs beginning from Gen 2 to Gen 4, also to be noted is the fact that the Gen1 to Gen4 Battery packs did not have any physical modifications or dimensional changes. The only change made was the replacement of the existing 22pin connector to a 36pin connector for vehicle communications or CAN Signals.

Gen 5 Battery Pack

Then Gen5 battery pack that is available in current models features a Output rating of 62kWh. Although the vehicle uses the same cells, the number of modules has increased from the 48 to 72, thereby increasing the number of cells to 288 from the previous 192 cells. This has been possible by using three different packings used to build the pack. This increase has also lead to changes in the dimensions of the Gen 5 pack, increasing 8 centimetres in height. 

Conclusion:

Nissan Ariya

The technology used in the Leaf and the battery research lead to a few one-off vehicles and concepts created by Nissan for example the Nissan Leaf NISMO which was debuted at the an invite only launch in 2020.  It is speculated that the upcoming Nissan Ariya would also use the same cells and battery configurations to keep up with the manufacturing costs and demands. Finally, it must be appreciated that Nissan has been a pioneer in bringing the electric car to the reality and making the concept feasible such before Tesla could break even with the industry and the formula of combining a simple body style and delivering a car at pocket friendly prices, certainly has made a mark on Nissan as the future of mass mobility and transportation.