What is the difference btw a 5 farad and 10 Farad capacitor? Will a 10 farad takes long to charge up to start the system (my main concern)?

 

ones just bigger than the other. 5 farad should be good for up to 5000 watts, and 10 farad should be good for up to 10000 watts. most caps stay charged when you turn your car off, so when you turn it back on, their ready to go.

 

Yes. The bigger the cap the more charge energy it takes to store and the longer it takes to discharge under load.