I'd stay away from 50W chargers. Go for something capable of at least 100W, 200W is even better. If you can't spring for a Hyperion the iCharger line is good. Get something that will be able to keep up with evolving battery tech. You might only run 2-3S packs in your Slash, but if you ever move up to something like 1/8 brushless that use 4-6S packs a 50W charger just won't cut it.