If the batery says 1 amp max then that's probably what you should limit it to. Too bad the ps blew up you could've gotten away with .75-.8 amps. Oh well.

If I had to power a 50 watt charger I'd use a cheap/old/free/ pc power supply. Most of them deliver around 70-100 watts real easily and can be up in shape in about 30 minutes. Maybe you know someone who has one lying around unused. My pc guy has boxes of them and if you search you can find ouit how to wire/convert them to rc charger use.

Second choice (if it was me) would be a real cheap 50+ watt ready made ps that had an output voltage of 12-15