Small plugs are connected to thin gauge wire and thin wire has high voltage loss and cannot carry respectable loads (amperage).
I do not recommend "factory" installed systems as they simply aren't efficient and don't work as well. Lots of vendors that install solar also do not do calculations to determine losses and use too thin gauge wire that make expensive systems only look good and do not perform as expected.
Solar is not difficult and one can easily learn everything you know to do it yourself! Basic mechanical skills are necessary and a cheap Ebay crimper really speeds things up! If you don't want to buy a one time use crimper, solder lugs, small propane torque and heat shrink tape take longer but work as well if not better. I crimp and solder my lugs which is a little overkill but guarantees things don't get loose with vibration.
Lots of internet examples (easy to google) of solar not working like it should and a little research is all it takes to design a great system.
Just a 1/2 volt drop in too thin wire can make the difference between a trickle charge and a fast charge. 10 gauge wire to a solar controller really has no place in any solar install unless you are running panels in parallel which increases voltage and decreases losses. Many installers don't do calculations to minimize voltage drop and use a cookie cutter build to save money (thick wire is expensive).
Here is a good blog.
https://handybobsolar.wordpress.com/...ging-puzzle-2/
Handybob blasts commercial RV solar intallers who do not take into account voltage drops that occur with wire length and thickness. Voltage is what pushes amps into a battery and many commercial RV systems just trickle charge batteries and don't ever get a battery fully charged.
A wet cell battery typically needs as a general rule of thumb the following:
14.5-14.8 volts for the Bulk Charge which ususally takes a battery up to about 90% state of charge. Many chargers (controllers) put out 14.2 volts
The last 10% takes MUCH longer and is called Absorption charge and is between 13.6 and 13.8 volts
After battery is charged it is put into a float charge voltage which is around 13.2 volts.
You can use your Zamp plug and portable solar panels but do measure voltage at battery to see how well it is working.
Side note: Handy bob uses very expensive equipment, controllers and inverters. I don't on my installs because you can get 90% of the performance from other equipment at 1/2 the cost which is a sacrifice I'm willing to make. I have a Renogy controller that puts out 14.4 volts per spec (actual is 14.2) and that is good enough although many higher end battery manufacturers recommend a higher voltage. I have a Samlex commercial grade inverter which is 1/2 the cost of a Magnum inverter and it is a true sine wave inverter. I make up for the lower cost products by minimizing losses from panels to controller and with all other wiring.