Our solar is connected direct to the batteries via a solar controller, the two batteries are also linked by a BatteryMaster so that the VB
is kept topped up as are the LB's. We chose that route as we found that without the vehicle battery was flat within 3 weeks due to things like the alarm, the clock and other items running 24/7 which cannot be isolated.
If you remove the VB
then the alarm is switched off as no power, that can cause problems as you may have to do am alarm reset when you replace it, of course it also means that your vehicle no longer has an alarm which might upset your insurance company if they find out.... I do not think (but do not KNOW) if the central locking function releases the door locks whe the battery is disconnected.....
You also must ensure that you have any codes for e.g. the radio since they also are likely to need to be reset.
IMO having a permanent solar panel is the best option (roof mounted), we used to use a 7w folding "briefcase" style solar panel placed in the windscreen facing South BEFORE I fitted roof mounted panels. That was just about sufficient to keep the VB
topped up (connected via crocodile clips) but only if the alarm was switched off....... see earlier comment about doing that.....
If you can connect to EHU, switching it on every week for 24 hours should ensure the batteries stay charged, if not, then look seriously at having solar panels fitted, or fit them yourself - they are not difficult to do.
I hope that gives you an answer, perhaps not as clear cut as you would wish, but it is a balancing act and I would be wary of removing the VB
, leaving the vehicle without the alarm.......