Advice choosing battery

Elmundopalladio

Finding my (electric) wheels
Dec 13, 2016
10
0
47
Edinburgh
Hi there

I've taken the plunge and purchased a TSDZ 2 motor (36v) and after a lot of reading then measuring I'm looking to purchase a suitable battery pack. My commute is 12 miles each way

My bike is a Moulton that I'm converting and it has limited options for the standard dolphin type packs. I'm not really up for a custom pack to fit in the web of the bike as waterproofing and ease of access comes into play.
I do have a long seat post which could easily take a bottle battery. The standard seems to be 10a, but there are some 15-16a advertised (U.K. Sellers) is it worth paying nearly double for 50% improvement in capacity?