Fixed and portable solar input into to 1 charging system

I suggest that the charge capacity required is relative to the power consumed from the batteries rather than the size of the batteries.
Cheers,
Peter
OKA196 motorhome

You have never been able to buy a retail solar panel without diodes in the panel - NEVER.
Even if there wasn't a diode in the panel, electronic solar regulators have never allowed the batteries to drain back - NEVER

I know he's gone now, but Dave B18 has missed the point.

Panels may be made with bypass diodes but to my knowledge none are made with blocking diodes.

Panels in parallel should each have a blocking diode in the output if it is likely that some will be in shade and some in sun.

It's not about blocking current from the battery to the panels. As Dave B18 suggested, the regulator does that.

It's about blocking current from lit panels in a parallel array backfeeding into shaded panels in that array. This happens within the array, before the regulator comes into play.

And the absence of those blocking diodes can cause hot spots in the shaded panel.
Cheers,
Peter
OKA196 motorhome

I have tested many panels over the years and found if the panels are of similar specs you only get a few milliamps flowing back into the shaded panel at its max output voltage. In my opinion if the blankets max output voltage is similar to the existing panels fitting blocking diodes would be a waste of time.

Alternatively, there is no problem using multiple solar regulators into the same battery, if that is a convenient solution or if the original regulator is fully loaded.
The multiple regulator approach also provides for some redundancy.
Cheers,
Peter
OKA196 motorhome

I don't believe that is correct, or at least, not always.
At least some regulators will shut down when multiple regulators are in use. Presumably, they sense the higher voltage (from the other regulator), assume the battery is full, and shut down.
Certainly my two portable panels do that.

I don't know about a DC/DC converter doing the job, but a solar controller would certainly be a help.

If your DC/DC converter had a solar input, then yes, but not all do.

Other replies have answered the OP's question, particularly HKB's.