I built a tab welder and want to up from ~13v to 16v for better penetration... the ebay 16v DC power supply I ordered is going to take awhile to get here (like 6-8 weeks doh!) and I'm impatient. I've got a bunch of wall warts laying around including a 7.5v300mA and 9v300mA. What's to keep me from wiring those two in series for 16.5v DC, which would be about perfect... if a bit slow to recharge... basic question I know, but have to ask anyway to make sure it's okay. 
