Purpose of Rectifier in Solar Tracker 5 Circuits

[Joster]

Hi John and Chuck,

Just curious as to what the rectifier is used for. I am referring to the one John points out here

http://youtu.be/y93IwhOGWB4

I'm a bit confused because its dc in dc out...I suspect it is for further smoothing of the DC but that's just a guess.

Thank you for your time,

Joe

[BobZilla]

Joe not all panels have built in diodes so I would guess this is there to ensure the batteries cannot drain back to the panels when it's dark.