I just got some new SLA's - they were a bit pricey, but they go far!
I went 50 km with them day before yesterday and they had a good amount of juice left in them still. They are 21AH batteries - 4 of them for 48V. They are installed in my scooter - not a magic Pie. Before that I had 4x18AH and I was barely getting 16 KM as well - found a runt cell and the batteries never did take long to sag and reach the min current.
Now I am trying to install 8, 12V 12AH batteries (2x 48V packs) in my Magic Pie bike... Hope to be done this weekend - I'll let you guys know how it goes.