🔍 What changed
This is the first version of the article, so everything below was added.
The **S** number is how many LiPo cells are wired **in series**. Each cell has the same three reference voltages, and the pack is just the cell voltage times the number of cells.
**Per cell:** 3.7V nominal · 4.2V fully charged · about 3.8V storage · ~3.0V practical floor under load.
**Common packs:**
- **2S** — 7.4V nominal, 8.4V full
- **3S** — 11.1V nominal, 12.6V full
- **4S** — 14.8V nominal, 16.8V full
- **6S** — 22.2V nominal, 25.2V full
A charger set to '4S' charges to 16.8V total because it balances each of the four cells up to 4.2V. Always match your charger's cell-count setting to the pack, and always charge in **balance** mode so the cells stay even.