What amp rate are you trying to discharge at? The simplest solution is to buy 100w 1ohm resistors on eBay. Then get a heatsink to mount them to and some fans to keep the heat under control. I made a simple one just because I didn't want my charger to bear the load of having to do it. I bought a Lipo low voltage alarm that I could set to go off when I reached my desired voltage. 4 resistors I use 2 of them in parallel to discharge my 2s Lipos and 2 in series for 4s Lipos. It doesn't exactly regulate the discharge current precisely but it is within reason because the 2s Lipos are discharged at a current that is equal to twice the battery voltage and the 4s is equal to the battery voltage. The biggest thing i have to be concerned about is the amount of heat tgis set up puts out. Which is around 150 to 180 watts. If i wanted a higher discharge current I would need to add more resistors. For the 2s Lipos I would add them in parallel. For the 4s Lipos it would be a much more complicated configuration. For the 2s Lipo 1 more resistor in parallel would discharge at 3 times the battery voltage and 4 resistors would discharge at 4 times the resistance. With all that said someone is selling a nice discharger right now for $40 if you are in America that does 30 amps.