Let's explore power tool batteries and voltage ratings. You may have noticed batteries labeled as either 18 volts or 20 volts. Surprisingly, these batteries are nearly identical despite the apparent discrepancy. Manufacturers use these voltage numbers as a marketing strategy. They label them as 20 volts to make them sound more powerful and appealing.
Here's the key point: both 18V and 20V batteries consist of 5 cells, each with a voltage of 3.6V. When fully charged, they average around 21 volts and drop to around 15 volts when depleted. Manufacturers opt for 18V because it's the nominal voltage.
Now, the crucial part: the small voltage difference doesn't significantly impact battery adapter use. You can safely use an 18-volt battery with a 20-volt tool, and vice versa. So, there's no need to worry about mixing them—they will function together seamlessly!