I'm happy charging it up, then using it the next day.  One launch per every second day is what I'm aiming for.

I have been charging my jumper battery on a std  artec(??) 230v charger for yrs now.. basically same as your battery(s)
 The amount of draw is determined by the internal resistance of the battery..
 So you can either simply plug a small std Pb charger into the wall of the camper, and charge it up.
 Your camper batteries and the solar unit will be far greater storage and current than you require
 OR
tap into the solar panel outlets, and buy a battery charging module.. About $40.. like I have on my smaller 10/20w panels and charge from there.. during daylight.

 The latter is just duplicating the charging modules you already have for your current camper batteries.. so go to the simple 1st soln.


Can you boil a full jug in the camper van? 2 or 3  times over a day?  or couple times in the evening?

 plug the charger into the 240v outlet on the van and charge it up.

Cant get much more simple than that...

 Did the batteries, kontiki come with a charger?.. out of interest.

Steps wrote: Although it will be charging from a solar panel, I have an inverter to convert DC to AC, so it will be like a standard house power point. I'm happy charging it up, then using it the next day.  One launch per every second day is what I'm aiming for. I have been charging my jumper battery on a std  artec(??) 230v charger for yrs now.. basically same as your battery(s)  The amount of draw is determined by the internal resistance of the battery..  So you can either simply plug a small std Pb charger into the wall of the camper, and charge it up.  Your camper batteries and the solar unit will be far greater storage and current than you require  OR tap into the solar panel outlets, and buy a battery charging module.. About $40.. like I have on my smaller 10/20w panels and charge from there.. during daylight.  The latter is just duplicating the charging modules you already have for your current camper batteries.. so go to the simple 1st soln. Can you boil a full jug in the camper van? 2 or 3  times over a day?  or couple times in the evening?  plug the charger into the 240v outlet on the van and charge it up. Cant get much more simple than that...  Did the batteries, kontiki come with a charger?.. out of interest.