A.Senior editor David Frane responds: The motor can’t distinguish between power from a nicad battery and power from a lithium-ion battery. And because cordless tools are designed so they won’t accept incompatible (wrong-voltage) battery packs, you’re safe using any battery pack from the same manufacturer that fits the tool.

The earliest lithium-ion batteries were not backward-compatible with nicad battery tools, but that’s changed over time. Three of the major tool companies — DeWalt, Hitachi, and Ridgid — now make 18-volt batteries that are both forward- and backward-compatible. Makita and Milwaukee 18-volt batteries, on the other hand, are not forward- and...

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