My drill just died mid-screw – battery or motor?

So I was driving some 3 inch screws into pressure treated lumber with my 18v drill, about halfway through the battery it just stopped. No weird smells or smoke, it just dead. The battery charges fine (led goes green), but when I put it on the drill and pull the trigger, nothing. Not even a click. Any ideas? Could it be the battery or the drill itself?

First, check the obvious – make sure the battery is fully seated and the contacts are clean. Sometimes sawdust gets in there and messes with the connection. Also, if you have another battery, try that. If it works with another battery, then it's the battery. If not, it's the drill. Also, check if the drill has a reset button – some have one that trips if it overheats or jams. If it tripped, you might need to press it to reset. And always wear safety glasses when inspecting, just in case.

Before you go buying a new battery or drill, check the charger. Sometimes the charger shows green even when it's not charging properly. I've had a battery that only surfaces charges, so it reads full but has no capacity. You can test by putting it in the drill and seeing if it runs at all. If nothing, try a multimeter on the battery terminals – you should see around 20v if it's fully charged. If it's way lower, you know the battery is the issue. Also, if you have a friend with the same brand, borrow their battery to test. That's the cheapest way to figure it out.

If it's a name brand like Dewalt or Milwaukee, the battery might have a protection circuit that shuts off if it detects a problem. If the drill stalled hard, it could have drained the battery too fast and tripped the circuit. Sometimes you can 'wake' it up by pressing the battery against a metal surface for a few seconds (but be careful, don't short it). Or just leave it on the charger for a while. If that doesn't work, you might need a new battery. But if it's the drill, I'd say get a new one – time is money, and old tools ain't worth fixing. What brand is it?