I have not seen this done. But it seems alright, I mean if it produces enough electricity to power something I do not see why it wouldn't work.
But, I have seen at Costco this exact same system for round 50 dollars! It comes with two solar panels, all the connections you need and the battery witch has 3 prong plug-ins directly in the battery so you don't need to hook up anything with a car battery! And I beleive that battery produces 150 watts!
I checked around, and the best option is to use used car batteries because they store enough
energy. To light up a terrarium I believe the $50 kit will not do the job too great, and you will
need a spare battery for sure.
I'm planning on using solar panels to light a few cages, so I definitely need a big panel, and a few
batteries.