Solar panels will give something like their full output if
Angled at sun
Cold
It isn't cloudy
You aren't shaded at all
Basically they don't work too well between October and March.
On a rainy day in winter I am looking at maybe 5-10ah per day from my 500w.
What you need to do is find a good way of monitoring your batteries, either with a cheap voltmeter and amp meter or a smartguage. Then you will know when to run your engine.
Half an hour is not enough. If that is all you can manage, do it every day in the morning to supply bulk charge, then hope the solar tops up the rest.
I can't stress enough that you need to learn to listen to your batteries, and charge them when they ask for it. Or they will die very quickly.
Good luck