A 30 amp discharger is the best if you have one built into your charger i.e. GFX. But not a must have. I usually use the 10 amp discharger on my LRP until I get my GFX in a couple weeks. I had one of the Indy Reactor 30 dischargers. That thing would get so hot, even with the fan on it, that it literally burned itself up and died after one month.