When I was looking for a way to replace the 12v gel cell I saw that system. By the time I bought the unit and the battery I found it was way to expensive for my tastes. Ended up with a set of rubber pads that allow you to slip in two 6 cell NiCad car packs onto the bottom of the starter. Think the pads were $2.50 a pair from Heliproz. I used 1800mah batteries and have no problem starting anything I own.
heliproz item number is KSJ454 Starter Bat. Pk. Holder