Laptop batteries are also multiple cells, simply encased.
Lithium Ion batteries have a cell voltage of around 3.7 V, that is driven by the chemical potential of the materials used.
It’s not possible to change that, **any** Li-Ion battery cell ALWAYS has 3.7V. Any device that wants more than 3.7 V to run, like Laptops or power tools, need to use multiple cells.
Power tools often used a pack of 18650 cells because these are a commonly available standardised size, so they’re comperatively easy and cheap to get as off the shelf components and integrate, and size isn’t a big constraint for power tools (unlike laptops, who don’t really want cylindrical cells cause they take up to much space)
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