LifePO4 upgrade

The current offerings in better lifepo4 batteries will power your go hub in the 10 ah size. But if you go for the really inexpensive ones from ebay then the 20 ah size is better since the larger size means the battery will supply the power with less strain on it. The real answer to your question lies in how far you need to ride. Though it can be easily done to go farther, I still like to use the 1 amp hour takes you one mile method for choosing size. That rule gets you 10 miles at full throttle out of a 10 ah battery, including a healthy reserve so you don't have to discharge it 100% every time you ride 10 miles.

The better vendors of lifepo4 batteries are Pingbattery, High tech bikes, and Ebike kit tm. Other options abound, more powerfull motors owners are liking the headway packs just appearing on the market. And lots of people are just using drill batteries like the bosch fatpacks.

For nicads, the packs from ebikes-ca are very nice. I have two 24v 8 ah packs that I run as a 48v 8 ah battery on a similar hubmotor. I usually get about 10 miles out of it, but 8 miles is a more realistic range at full throttle. The other day I rode 20 miles at slower speeds, including a 800' vertical hill and lots of headwind. I really love the lifepo4 for my daily rides to work, but the nicads are ideal for my weekend bikes since they can sit around unused for months with no problems, no issues with bms, etc. They are a little bit cheaper than lifepo4, and they do work pretty good. Lighter than lead, but still pretty heavy compared to nimh or lifepo4.