I have two of these kits tied together with a 1200 watt inverter and a 115 Amp deep cycle marine batt. I have been getting between 96 and 313 watts per day from this design. I use this to power my living room; TV, laptop, and Dennon Audio system. On a sunny weekend I can get over 26 amps a day into the batt. (If anyone cares, I can get pictures out there for anyone to see my setup.)
In my case, the buzzer was telling me there was too much voltage a the PV. I burnt up my diodes and the MOSFET after a full day in the sun and a full batt.
I'll get you all better details as soon as I find my notes but here is what I remember about my controller I tore apart and traced:
It is more of a voltage regulator than a charger. As long as the voltage of the PV is above the batt voltage, it will charge. If the PV voltage exceeds a threshold it shorts to ground through a simple MOSFET circuit.
There is diode protection. 2 in a series immediate after the connection post. If the switch is on the PV+ (after the 2 diodes) is then tied to the Batt+. The PV- and Batt- are common when the switch is on.
In short, find a real charger made for PV applications. I replaced mine with a Manson found on e-bay. It has good historical and current data for display and can be remote switched off/on.