I've been trying to rework my solar requirements but have to admit I'm not certain even with the spreadsheet, as to what I need.
Just did an offgrid calc on another site and was given 500watts of solar power as my needed bank using 15k watt hours per week in my zone. However when I use the sheet and plug in Surrette S530's I end up with a lot more solar power required.
I'm wondering this: is the AH rating asked for the 20 hour rate or perhaps a different rating? After all, many batteries list up to 100 hours. The difference? The 100hr rate is 532AH where as the 20hr rate is 400ah.
Not sure that matters a whole lot but I'm wondering.
Here's my situation: I'm running 8 GCB's (~220ah @20hrs) and can draw them to 50% in one evening of using my fridge and lights if it's a particularly dark day if I assume (I know I know

) the lights on the Charge Controller and Inverter are correct. The logs might show a discharge of more then that even but I've learned that under a load the batteries show a lower voltage then when the load stops (i.e. the fridge running can show the bank at 50% until it stops where it jumps back about 80%).
I'm certain that I DO NOT have more then 2 days to 80% of real discharge but with lots of sun most of the time it isn't an issue because the bank charges back up the next day so I don't usually see anything near that.
My system is 615watts of solar panels in series running to a Morningstar 60MPPT controller. It's a 12vdc bank @ 880ah and my calculated weekly usage should be about 9000 watt hours. Though the controller logs suggest that could be as high as 12000 watt hours.
I've drained the bank down badly last winter (voltage reported as low as 9.9vdc) and plan to replace the bank but also want to make sure I don't ruin the new one.
Thanks for the help