Can you use a 12volt car battery charger to charge a 18volt cordless drill battery?

I'm actually charging my 12V sealed lead acid battery with a laptop adapter which output is 19V, 2.1A. I'm not sure this will shorted the life of my battery or not, but the battery hold the charge.

I don't have a voltmeter to test the voltage, but the battery can light up a 12V car headlight light bull. So, I guess it work.