It looks like the specs are 30 amps. Voltage and current are key parameters for your build. Too much power and your will melt or brake something, too little and you wont' get the performance you want.

The controler you linked to was 30 amps.

The LED screens are not particularly useful for lifepo4 batteries, as they tend to hold constant voltage and then drop fairly fast. I hear they make more sense with li-ion or maybe lipo. As my terrain is pretty consistant, I know I can go 25 miles, so I just use that to judge my range.

You could also wire an inexpensive watt meter to allow you to check how much power is left with your battery.
http://www.ebay.co.uk/itm/New-Digita...item2a28384842