A solar panel to Solar Charge Regulator aka Controller acts as voltage regulator allowing batteries to charge without overcharging from panels.
7 amp hours at 12 volt = 12 watts of continuous usage for 7 hours OR 7x12 = 84 watts for ONE hour. 7 amps of current at 12 volt is 84 watts. Most regulators figure somewhere between the charging battery voltage and the open voltage or right at the top of a fully charged battery. 7 amps x 14 volts (fully charged battery) = 98 watts rounded to 100 watt MAX!
Some older batteries that are in poor condition, like the one I am using in this video, draws current less effectively, this is why it is only receiving 38 watts. Also, the wiring is not proper for a real installation and the panel is not at the optimal angle to the sun, this is just to show you what a "Charge Regulator" does.
It is easy to forget!!!!! I had toxic gas smelling up my yard from a smoking battery I hooked direct in the morning and by 12 noon it was destroyed! Dangerous and stupid, BY A CHARGE REGULATOR!
A fully charged 12 volt battery is 12.6 - 12.8 volts at rest and 13.6 - 14.0 volts while charging.