I vastly doubt you are using 30 amps per day on your weekends away. I would think your 75 Amp hours house battery is fine.
I like to keep mine well above the 50% much better is 12.3 or 12.4. Thats about 70-75%. Use a multi meter stuffed into your cigarette lighter socket to check the battery
12.65 V 100%
12.45 V 75%
12.24 V 50%
12.06 V 25%
Also remember, when you are using power on your boat during the day you are still charging with your solar panel, so what you are using is 'free'. Your draw is only at night
But I would rather buy it in person to get the know-how and answers to my questions.
I agree with you. I like to touch, feel, read the instructions, go home and think about it etc. Its worth the few extra dollars.
This time ( since I am 'building' my power layout ), I want to do it right!
Nothing is going to blow up, so just experiment
A cheap multimeter is about $25, get one with a digital read out. Don't be afraid to run the battery under 50% is you are testing for a weekend. One deep discharge won't hurt.
Cheaper Solar controllers are $36 Solar Charge Controllers - Budget Marine
Solar Panel (seems expensive!!) 80-Watt Solar Panel, 4.67A Max. Amps @ 15V, 47.28"L x 21.14"W x 1.81"D $549.00 Polycrystalline Solar Panels 80 Watt Panel, 4.67a Max. Amps 15v, 47.28"l 21.14"w 1.81"d
You should be able to do better than that.
the 5 watt and 15 watt panels are toys. Won't even run a vibrator.