How do stacked batteries work?

https://www.ecelibattery.com/how-do-stacked-batteries-work.html

How do stacked batteries work?
Stacked battery is a battery system made of vertical or horizontal superposition of multiple battery packs. Together with inverters and photovoltaic panels, it forms a household energy storage battery system to store electricity generated by renewable energy sources such as solar and wind power. This stacked battery technology is used to ordinary home and office uninterrupted power supply system; for various household appliances such as air conditioner, TV, refrigerator, electric rice cooker, hot kettle, lighting, and digital products and medical equipment.

So how do the stacked batteries work?

The system is mainly composed of four five kWh battery packs in parallel, combined through the power lines and the communication lines behind the battery pack, with a total capacity of 20kWh.