If the batts are at half capacity, then it would take less time for the solar to raise their voltage. As voltage rises on a 12v panel you get fewer amps (as per IV curve), but not a lot fewer until voltage gets closer to 15. So I am not understanding this very well.
The lower capacity should make the battery charger taper sooner, not later. Again this is confusing.
Without some measured numbers using say a Trimetric, it is hard to get a grip on the situation.
Not being able to get the voltage higher than 14.5 using the same amps on half the capacity seems counter- intuitive.
Paralleling the engine battery with dubious house batteries is very brave! :) I don't know what that means where the "morning voltage" on the whole bunch is then " ok" What is "ok" in voltage? If the house batteries are shot, ie they would otherwise sink to a low voltage overnight, then how can the teeny weeny engine battery hold them up?
Very confusing situation! Anyway, the main thing is you are still in business, so something must be going right.
