There are some instructions in the Ctek manual..
 Also , well is on my unit, where you select motor bike, car think another 2 above .
 If anything is wrong the red light in top left cnr comes on.
 Thu have found on some batteries it has come on, check polarity and stuff, all good then goes off and few hrs later battery is at maintenance and good..
 I would be hesitant to charge from 'flat' charge' both at the same time.. thu charge or even top up one at a time yes.

If once the little indicator lights reach to 'maintenance' and if both batties are in parallel, and identical and about same age/ condition... then maintain both together..

Cant rem off hand mine I  (think is about 4amps ???) handles our about 760/ 780 cca nps ( not sure what it is exact other than its a good 200cca above engine requirement) ....also does the still ex factory 4x4 deisel ute nps.. not sure what that is either without going out have look

Depending on level of your battery charge, they don’t like to be to flat. You will need a charger with an output of 14.8v, the larger Cteks have this range, so you will need to check your charger specs.

Bounty Hunter wrote: does the battery manufacturer provide any documentation with recommended charging voltages/currents? - and how do these details compare with the output of the Ctek model you have? probably best to start with manufacturer supplied info rather than internet opinions from 'who knows where'  - batteries are expensive and you dont want to shorten their life inadvertently.