Re: Matching Battery Bank Size to Panels
Just for illustration, since both posters here have similar situation to mine.
We run ~400 watts of panels (depending on how you count the name plate). We run that through a Rogue 3024 controller, into 4 225 ah T-105 trojan batteries wired for 12vdc, leaving ~450 ah of battery.
On an average day, we draw the battery down ~60 ah by morning, sometimes as little as 30, almost never more than 75 ah. So on average we draw down ~ 15% every day. In addition, we do significant load shifting so that we recharge laptops and do web work during the day, pump water during the day etc.
Our panels get into full sun ~ 8:00 AM between the equinoxes. The panels are essentially dard by ~2:30 PM between the equinoxes. Because of odd peculiarities in our panel arrangement and shading almost never do all the panels get full sun at the same time. The front wall mounted panels get sun very early, but have partial shading through out midday. The roof panels get full sun ~ 10 and loose it at 2 or so, but have no shading. Depending on the season, they get some late evening (4-9pm sun) but I don't count that in any calc. So when everything is firing right, the rough puts ~300 watts/~ 20 amps for the bulk of those hours. I sometimes see ~375 watts and 28 amps, but that is the exception. On an average (full sun day) we harvest ~ 1.2 kwh/day (or ~80 ah/day).
So the 20 amp average charging rate is only ~ 4.5% of the 450 ah capacity of the batteries. Would I like more? Of course, but my system works just fine. I do think that any less would be net/net not enough, but that said, we lived for years with only 200 watts, and the batteries have lived 10+ years.
Bottom line, I wouldn't get too hung up on the % charge rate (within reason) I would pay attention to the batteries on a regular basis.
Please note, being a moderator does not add any weight to my opinions 300 watts Siemens/BP panels,plus a Sun 90,, making ~400. ~30 amps into Rogue MPT-3024, 450 ah of Trojan T-105, Morningstar ts300 inverter, a Tri-Metric meter.a collection of antique generators, plus 2 Honda eu-1000i's (also a BS2512 IX controller) and assorted other stuff!