Do Volts Help to Compare Cordless Tools?

My old Makita cordless drill uses 9.6 volt NiCd batteries. The batteries are dying, so I'm trying to decide whether to replace them or upgrade to something new. Is my 9.6 volt tool weaker than a newer 18 volt model? There isn't enough information to tell. 2 amps at 9.6 volts is more power than 1 amp at 18 volts. What does any given tool use? Volts, as advertised today, are mostly just sales talk. I agree volts indicate a trend toward improved performance among responsible brands. But imagine choosing a car based on its fuel tank size. How far can it go? You also need to know its fuel consumption rate.

I was in a store recently and a nice fellow representing another brand was helping explain some of the features of the various products. We were looking at 18 volt kits. I said it was for home use, so he asked, "Have you looked at 12 volt models?" I understood that he meant lower power and lower cost, but I answered, "Voltage doesn't tell me anything. I need to know the watts."

He became very interested in learning what I meant, and studied a couple of brands' labels carefully, looking for some clue to the actual power of the tools, but found none. He did find the watt-hour rating on a battery. That's useful for comparing battery capacity within a tool family, but without knowing the tool's current demand, and the battery's capacity to deliver amps without overheating, you can't accurately compare across products.

It is true that a higher voltage can deliver more power for a given current, and thus for a given motor winding design; that's how our power distribution grid works. So generally, more power is available from higher voltage; it's just not always the case that the device itself can use that extra power.

I finished my lesson by pointing out that a lightbulb may work on 120 volts but that alone doesn't tell you if it's 40 watts or 100 watts. He asked how he can learn more. On my phone, I showed him that a search of "basic electricity watts" delivered links to introductions to the subject.