What’s Inside a Tesla Model S Battery? 

The world marveled when the Model S Tesla was released with its 18650-type battery. Here was an EV that allowed drivers to travel up to 405 miles or 650 kilometers on a single charge. While many Tesla owners are simply happy to enjoy this feat of engineering, others want to understand it better.

Today, we’re going to take a tour of what’s inside a Tesla Model S battery.

The Smart Structure of Tesla’s Model S Battery Pack

When the Model S was designed, not only was an innovative battery designed in terms of performance, but also in terms of how it contributed to the car as a whole. Sitting in the underbelly of the car, the wide, flat battery pack serves to strengthen the vehicle’s structure while bringing down its center of gravity, thereby enhancing stability.

The Model S battery pack is comprised of up to 16 modules that sit inside niches in a base with fire protection in between. Each module contains six blocks of 74x 18650-type battery cells, so a total of 444 cells per module. A central bus bar connects each module to the car’s Battery Management Systems (BMS), which monitor the state of charge, overcharge, over-discharge, temperature, and more to ensure maximum battery efficiency and longevity.

Each battery module has its own BMS, which is, in turn, controlled by a master BMS. This master unit communicates with the vehicle’s Engine Control Unit, allowing you to conveniently explore your Tesla’s battery status using the dashboard touchscreen.

Battery Specification of Tesla Model S

The 18650-type battery cells used in the Tesla Model S are lithium-ion cells made for the brand by Panasonic. Each one features a graphite anode and nickel-cobalt-aluminum (NCA) cathodes in an electrolyte solution of lithium salts.

The battery’s name comes from the measurements of each cylindrical cell, which include an 18mm diameter and a 65mm height. Each cell has a capacity of 3.4 Ah and a nominal voltage of 3.66 V. They can hold 12.4 Wh of energy and have a mass of 49g.

If you’re wondering why the 18650 has an ‘0’ at the end, whereas the other Tesla battery types do not, that extra zero is said to represent not a measurement but rather the cross-sectional shape of the cell.

Energy Capacity Ratings Within Model S Tesla Battery

Cell Energy (444 per module, or 6×74)12.4 Wh
Module Energy (up to 16 per battery pack)5.5 kWh
Battery Pack Energy (1 per vehicle)90 kWh

Each of these small cells is used to construct a Tesla Model S Battery module. This requires six series-wired blocks of 74 parallel-wired cells, so a total of 444 cells within each battery module. In turn, up to 16 modules are used to construct the full battery pack of the Model S Tesla.

Offering the highest performance of any Model S, the 16-module battery pack of the Model S P85 accommodates the aforementioned 405 miles or 650-kilometer maximum driving range.  

In terms of safety, beyond the housing that physically separates each module, Tesla’s cells are connected using a wire bonding technique, with each wire also serving as a safety fuse. In addition, there is a liquid cooling system that interlaces the cells within each module. The water and glycol solution within this cooling system disperses any local heat build-up, reducing the risk of a “thermal runaway,” which is what causes fires in lithium-ion batteries.