On Monday, November 30, 2015 at 12:45:24 PM UTC, newshound wrote:
Anyone got any experience with them, or can recommend one? Only for a
1.3 petrol engine plus general use as a mobile supply.

This chap has a few videos on making car batteries with lithium
cells and supercapacitors:

https://www.youtube.com/watch?v=z3x_kYq3mHM