Exploring How Ola Makes Its Battery Pack For The S1 Pro

From stacking cells to intelligent battery management system, here’s how the S1 Pro’s power source is made

We were recently invited to Ola Electric’s FutureFactory at Krishnagiri district in Tamil Nadu. As motoring enthusiasts, factory visits are always fascinating to us. However, a chance to peep behind the curtains of one of India’s biggest names in the EV space is a bit special.

It is at this facility where Ola makes the S1 Pro electric scooter. It will also serve as the R&D facility for its upcoming range of affordable scooters which will feature cost-effective, yet stable, LFP (Lithium Iron Phosphate) cells.

Here’s a quick lowdown on how Ola builds its battery packs.
   
Step-1: Building the Core
Cells form the core of a battery and currently, Ola uses Lithium-Nickel-Manganese-Cobalt-Oxide (NMC) cells. Sourced from Korea’s LG Chem, the almost banana-shaped battery pack comprises 224 cells that are split into two clusters of 112 units each. This non-removable pack has been designed keeping Indian riding conditions in mind.

Each manufactured cell will typically deviate from the preset output levels by a certain degree. Hence, in order to get maximum performance, optimum charging and consistent discharging capabilities, a cell is grouped with others sharing similar output levels. If a cell does not meet the pre-decided parameters, it is discarded. Via automation, the cells are stacked on a plastic frame and later stuck with a special UV light-sensitive glue. The process is precise and quick to ensure the glue bonds properly.

Step-2: Connecting the dots

The next stage is to line the plastic frame with an aluminium ‘bus’ rail. To conduct electricity, the cells must be connected to the bus via a technical wire bonding process. Interestingly, this allows the wires to double up as a fuse as well. Therefore, if one cell fails, the fuse blows isolating the damaged cell from the rest of the cell-bed. This lowers the chances of the damage cascading and causing the infamous battery fires that are notoriously hard to put out.

Step-3: Letting it breathe

The next stage in the process is cooling. The 3.97kWh battery pack must be thermally regulated by the process of passive air-cooling. Here the base of the cell bed is cooled by conducting the heat away from the cells using a special plastic that has nearly five to six times superior thermal conductivity. The team at OLA has chosen plastic over aluminium to keep the weight low. The case itself has air fins much like the ones found on an air-cooled IC engine for additional thermal regulation.  

Step-4: Making it aware
Each battery pack has 25 sensors continuously mapping the unit’s voltage, current and temperature.
This data is sent to the EV’s battery management system(BMS) which liaises with two onboard computers, one for each function. One manages the cells and  the other, Artificial Intelligence (AI) which in turn manage the overall performance of the EV.  The final layer on the battery is a metal panel that’s connected to the BMS to keep its components cool. 

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Each battery goes through a rigorous quality check measuring even the torque applied to each screw. This ensures the pack is sealed well and after the precise fitment of each part, the battery pack is IP67 rated. The process of making EV battery packs for two-wheelers is clearly not simple and unlike in cars that offer superior ventilation, limited space on EV scooters and bikes are a real challenge. If the internal pressure from the unit crosses 300 millibar or 30kPa, the system is activated, and a special ventilation system on the Ola allows the hot gasses to escape easily. But that renders the pack out of commission and hence the venting system is designed to minimise the impact of failure, but sadly it cannot prevent it.