Re: Charge Controller and batteries for solar panel
Breaker or fuse should be located near the battery bank. If you're going to use a breaker, be sure it has a high enough AIS rating...at least 5,000 amps. I believe only the new, special Blue Sea Systems breakers have this.
If you're going to use a fuse, make it an ANL or a MRBF, located near the battery bank.
The Concorde Lifeline GPL-4DL is a good AGM battery. Hope you're upgrading your charging capability. These AGMs can easily take five times their AH rating when 50% discharged, i.e., the 210AH GPL-4DL can take 1,000 amps or more for a few minutes before dialing back. Four of these could potentially take 4,000 charging amps!! Obviously, this isn't possible, but to get the best from your AGM battery bank you'll want to beef up the onboard charging capacity as much as you reasonably can.