I run four chargers to keep four cars running in four classes.
I use a 50W charger to top off my 220mah LiFe packs in two cars.
An iCharger 250W, a FMA Revelelctric 50W, and a Pro-Tek 200W to charger the main packs. Yes the FMA is only 50W but I'm only topping off a 1S pack with it for about 1,200 mah so at 4amps it doesn't take very long, about 30 minutes.