DIY eMTB Battery Capacity and Voltage?

[Old & Slow]

I'm putting together a DIY eMTB to ride the local trails. Trails I used to hike but don't do as much anymore. Most of the trails involve 1-2K of elevation gain and no more than 20 miles total. Just me and the dog going slow, he can easily do 20 miles, I can't. Might do multiple days w/o the ability to recharge.

Planning on converting my ghetto mtb at first, then upgrading to some form of FS mtb later. I've already ordered tools to removed the crank arms and the bottom bracket. I will use one of Bafang motors with programming to suit my style.

Many choices as to battery capacities:
36V 17AH
48V 12AH
48V 17AH
52V 14AH

Since I have no first hand experience, how do I choose?

 

[PierreR]

Higher voltage is almost always advantageous.

 

[boss]

If you have a BBS02, you'll need 48V or 52V (BBS01 is 36V). 52V provides more power, but most battery gauges on the display are set for 48V and don't provide accurate information with 52V (Luna has one that will, but the stock Bafang won't). If charging might be a problem, use the higher amperage battery. 48V, 17 ah = 816 watt hours which should be adequate for two 20 mile rides (2 - 3,000' ascent) if you pedal moderately. For comparison my BBS02 consumes about 300 watt hours in a 15 mile ride with 3,000' of climbing, but I pedal as much as possible.