I just put my 18V Makita inflator to the test by airing up the forklift we have at work. It had no problems reaching 4.5 bars. I was aiming for 5 but it's too damn cold out.

This is a lot better than the house brand one we sell, which including battery and charger is a couple tenners cheaper than the bare Makita tool.
The Makita requires you to stand there and hold the trigger, though. Our house brand one doesn't, but you can't leave it unattended anyway because as soon at it reaches the desired pressure and turns off, air starts leaking back out through it so you'll come back to a tire with less air in it than when you started.