You got that right. And since engineers design to limits, it's pretty UNlikely a 12V unit has 18V components. Nine to 12 maybe, but not 18. These guys must be loved by the battery and replacement parts shops, or they use their equipment a few seconds at a time once or twice a year. Then, even IF the components can live thru 18V vice 12, it's a pretty sure thing the motor/stator windings weren't designed to dissipate that much heat. Sooner or later one of these guys will set the drill down after a prolonged session, the core temp will work its way out thru the windings, and drip possibly flaming plastic or winding cement onto the bench, and start a fire with it, and then blame the manufacturer for their house burning down. Way too many people think batteries are "safe" and that they never heat up. The best part is the failure of a 12V while it's on an 18V charger; it's usually a pretty site, at first. When a battery core's max temp is exceeded, it almost always explodes or vents with great gusto, especially the types used in power tools. If you want to see a really pretty site, try a lead-acid on a bigger charger; it's prettier yet, all that carbon to burn off. Watch someone come back and say those batteries can't vent 'cause they have no vents .
Don't drink & drill.
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