For information - The emoncms.org GUI export uses calls of form
(Taken from comments in the code)
// Export multiple feeds on the same csv
// http://emoncms.org/feed/csvexport.json?ids=1,3,4,5,6,7,8,157,156,169&start=1450137600&end=1450224000&interval=10&timeformat=1
To ‘see’ what export URLs are for you, complete the fields on the export form, disconnect your network (Flight mode on my laptop) and click [Export]. It will fail leaving the URL displayed.