I’m wanting to install a small Solar Panel to drive a 4A, 12VDC fan.  The Solar Panel has an output of around 19-24VDC.  I’m concerned to know IF there is a problem with a Buck-Boost Converter Module when the sun goes down and the Panel voltage starts to drop.  I was looking at the F36W12V5A3S module… but some say that the Voltage spikes to around 30V when the voltage gets too low… I don’t want to burn out my fan!  Any comments appreciated!