hi guys i'm looking to buy a small solar grid-tie kit for school. i need to connect it to a battery so it will store the energy that created during the day and during night to use it. if the battery will run out of power ,it will pull some from the electrical grid and the load wont "feel it". does someone knows where can i buy one ?

You will need four parts of this kit :
1.solar panels
2.controller
3.converter
4.batteries
principle figure will be this

1.solar panel --------->2.controller -----+---->4.batteries -------->DC device
                                                            ↑
                                                            |
power grid --------->3.converter --------

At day time ,solar panel output electricity feedback to the converter ,then the converter will cut the power grid out .

i have the :
Xantrex Prowatt 300 Inverter -

Rostec
>
- RC12-20 battery
steca solsum 10.10c charge controllers
Solar panel made by SunWize Solar Power Systems , size of
597x540x25 mm

and i'm looking to buy the controller or some kit, does anyone knows about basic small kit for it ? i need it for demonstration on two small engines.