Thanks! Did you modify the controller yourself? or bought it off market? I am not so worried about the battery life as I have enough time to recharge my battery everyday. And I use only 15 miles a day. What I am after is increasing speed with the existing equipments, use the maximum potential of the current setup. I don't mind getting a new controller but not keen on spending for a new battery or motor. Currently I get 17-18 mph on peak battery. Would be nice if I can achieve 20mph by increasing the controller Amp.If you want speed then more volts is what you are after, 48v in lion form its possible you may get up to about 23mph with 250w. A higher amp controller will give you more torgue/pulling power and climbing ability but will reduce battery range.
I have 3 250/350w drives and controllers 15, 18 and 20a. All cruise nicely on the flat up to 19mph and can get me to 22-23mph with some harder peddling, a really fit cyclist will be able to go beyond that but if they are that fit a normal very light bike is best. Higher gearing ranges will also add speed but again you need to be quite fit and have the stamina to maintain speed above the pas cut off.