For what it is worth, I added a second battery bank to my C-27. I have a 128Ah Deep Cycle Lead Acid bank that was my original house bank. I opted to add a new, independent bank for my electronics and I am transitioning all of my house use to it so the original bank will be for emergency use and motor starting only. The second bank is a 184Ah AGM bank with two cells.
I picked up two cheap Sunforce solar panels and their 7A charge controller off Amazon for what West Marine was charging for the one large panel alone. I got their small trickle charger panel and their 15W charger panel. The small panel maintains the engine batteries and the large one is used to charge the AGM house bank.
The charge controller works well as does the panel. My cells took a couple weeks to get to full charge but it has been remarkably easy to install along with the new circuit. It's been very trouble free and is installed nicely hidden away under the cockpit.
If you're looking for a cheap solar option, the Sunforce panels do work. Not as good as a quality single crystal cell but I'm also not going offshore with them. My install costs were reasonable for what I did. Switch panel, master switch, battery fuse, bus bar, terminal strips, wire and all connectors plus tools.
SV South Paw
2000 Hunter 340
South River, MD