I've been using those starters on 50 and 60 cc engines. I have a Zenoa G62 and a friend used the Megatron on his DA 50's.

Those 12V gel cell batteries are only $5 ea at the ham radio swap meets and at the surplus store up town.

Here's a video of Mac Hodges using a Dynatron/Miller with two gel cells on his B-29 which uses four ZDZ80 twins

http://www.youtube.com/watch?v=S0DxPo5tWGg