I'm considering on buying a 12v GSM Controller with 2 relays that can power 30A, 220VAC, 4000watts each. I want to control a 12v utility pump which consumes 12 volts DC, 5 amps, 50 watts. Is this overkill? Can the GSM Controller handle this task easily?
That depends on whether on you think buy something with a rating 80 times what you need is overkill..
The voltage rating is far higher than you need but that hardly matters. The current rating is substantially larger than you need and that's a good thing - it means the relay is likely to last longer.
I haven't looked into the controller you're proposing to buy to see whether it's capable of controlling those relays. The controller would need to be able to supply the voltage and current needed to operate the relay coil, and it would need to provide flyback protection. If the controller is designed to operate a relay and supplies the right voltage to operate the relay you're using then it should be fine.
Thanks for both your input guys! There is also a GSM Relay Controller with 7 channels 250V 10A 50 Hz relay contacts. However, I didn't read anything about a quad band GSM receiver. In getting the industrial grade GSM Relay Controller I could update my project to stronger more powerful hardware, such as, a pump with requires 1/2 horsepower. I'm thinking to power the project with a single car battery.