We now carry in stock two less expensive infineon controller options that use 60V transistors. These units cannot be modified for 72V, but for those sticking to 36V or 48V operation they are good value. We have a small 6 mosfet controller that has a 20A battery current limit and a larger 12 mosfet version with a 35A rating. Both are available independently and as options for the Nine Continent kits.