damn just get a small honda gen. they have some real small gas one that you cannot hear them run !!

 

Go to a camper/boat dealer and get an isolator. you connect two batteries to it to keep them charged but can use one as the starter battery and the other as an accessories power source. I did that with my boats in the past to camp overnight and run stuff so that I could still start the boat at the end of the weekend.

I think I got it from J.C. Whitney, but that was a long time ago. It is aluminum fins with three post to connect to. center post is the wire from the charging system and one lead each to the two batter + post. Underneath is some diodes. they last forever.

 

And what size would those be ???

 

The ones I have seen are the same size as car batteries, but may be bigger than a bike battery. They are called leisure batteries here in the UK and can be bought at boat, camper and trailer centres. Should be easy enough to google!

 

The factory battery is too big already. Any increase in size, would be counter productive.

 

I think I would rather ride. I want to listen to the motor not the radio. But I guess if it makes you happy, hook up another battery. If you hook up three will you get a solid thirty minutes?