You are right on both counts (high charge voltage and long charge time), but it's required. It turns out the Surrette super-duper mega-moster batteries really aren't a good match for a solar system. They are more suited to large commercial vessels, trains, and other applications where charging is via a prolonged charge source. Solar, by it's very nature, only lasts for a fixed number of hours per day.
It turns out that the very thick plates in the big Surrettes (series 5000) want a really long absorption charge. 6-8 hrs would be ideal, and that's AFTER they go though their bulk charge phase. Well, around here the sun don't shine that long every day. After extensive back and forth with Surrette, I settled on just under 60V as the bulk/absorb voltage. That's equivalent to 15V on a 12V battery. It's a super hot charge voltage, but the only way to get the SG back up in the available time. And it's not like I'm draining them down very much, or that I'm short on charge power with 3600W of panels. This has been a real source of frustration, and I deeply regret having bought the batteries and feel Surrette really misrepresents them by selling into the solar market. But they are mine now, all $14k of them, so I live with them as best I can.
FWIW, my goal is to have sorted out a LiFePO replacement by the time the Surrettes give up the ghost. They seem very promising, but the charging and control systems still seem immature.
Oh, and the water consumption is WITH Hydrocaps. I put them on years ago.
