That is pretty much the definition of a UPS system.I would envision I would be at the other vertex of the triangle. Near 0% discharge most of the time, and near 50% a few days a year.
Not me--but probably true to a degree... Although, it is almost people are handicapped by old ideas. Leads them to a large battery bank with small charging resources (less than 5% even). And when they "ran out of power", the recommendation was a larger battery bank (yes, that was common advise not too many years ago, and probably still true in some areas of the Internet/off grid resources). Adding batteries instead of charging resources--was still a bad idea back then, and still is now.Was it you who said (in some other forum) about a generational difference in off-gridders. The old notion was "batteries cheap, panels expensive" , but now its the exact opposite
Presently battery monitors are (for the most part) not integrated with charge controllers... So, other than a programmable alarm (for limited type of events), the typical battery monitor is to inform the system owner about the present state of charge of the battery bank. I don't know of any Battery Monitor that can warn of "over charging events"... (not that I know much in details about monitors or what is available).What about the fancier battery monitors?
A battery monitor will not be a substitute for a remote battery temperature sensor controller charge controller.
I tend towards recommending small AC UPS for computers (UPS's have losses--I don't want to waste the power to provide a UPS for my fridge and microwave/toaster ovens so I don't have to reset the clock)--and a "balanced" off grid solar PV system for balance of home (with conservation/power management for motors via choice of motors/systems and/or VFD type controllers).Another reason for AGM batteries for the setup I describe (better for providing possibly large wattage during transient events)
In the end, you will probably do several designs and compare the cost/benefits for your needs. And they probably will not be black and white type answers.
And how much planning/equipping do you do for a once in 100 year event? Our last 1 week power outage was in the Mid-1950's. The rest have been for a few hours every couple years.I figure 2-3 year life for a UPS, at $100 a pop. Which is one of the "economic" reasons for seriously considering some kind of "batteryization". In fact, up until our friendly neighborhood dereecho provided a refresher course in coping with extended outages, the bigger reason.
We have "the big one" (earth quakes) every 100-150 years.... Last "big" one was in 1907. Earthquakes tend to have very scattered heavy damage among almost no damage. "Earthquake" proofing an older home is a much better idea here vs adding a entire off grid solar capable system.
Two is always better. Spare and a backup. Plus you can always "barter" fuel/unneeded genset/electricity if ever needed. Plus the larger genset can be useful for power tools/AC etc. when needed and convenient (fuel availablility, etc.).I figure I am going to need a genset -- and I got one already (though I might ditch it for a honda eu2000).
Assuming install a large GT system (or Hybrid GT system)--Yes, Net Metering and SRECs will help reduce overall system cost (plus tax breaks for "whole" solar system vs smaller UPS plus smaller solar system which is not 100% tax break compatible).Definitely have net metering up here. And, quite importantly, SRECs. So value of electricity sold to the grid is > retail cost. Achieving optimality may not be possible for both functions, but reasonable efficiency should be achievable. I posit that will be cheaper & easier than two seperate optimal systems.
True, the amount of time you would spend on GT/OG "bang-bang" charging will be low... So battery life will be unaffected.The suggestion by stevendv (http://www.wind-sun.com/ForumVB/show...056#post123056) to have a transfer switch to select GT > main_cb_panel or GT -> inverter/charger_subpanel is interesting; it might remove this concern (99% of the time the battery is being properly charged (if charged at all) by the inverter/charger.
I am a big believer in looking at maintenance (costs, time, debugging, locating old/obsolete parts vs forced upgrades, etc.).
A whole home UPS--replace batteries every 7 years or so, repair/replace electronics after 10+ years (for the most part, 10+ year old "high-tec" electronics are not repairable as vendor has cut parts/service support and electronic compenents are not available on the open market, etc.
So--Figure on saving cash for new MPPT controller, new GT controller, new Off Grid inverter, every 10+ years... New battery bank every 6-10 years. And look at the energy costs (loses, battery charging, conversion losses for UPS's, etc.).
Not saying it is not worth it for you... Just that you will be replacing 2/3rds of your system every 10 years or so.
VS me--use laptops (have own battery), small $100 UPS every two years for one desktop system. And buy a new Honda eu2000i for $1,000 every ten years (if it still runs--I now have spare/something I can loan out for non-emergency use).
Buy 20 gallons of fuel and preservative once a year, recycle old fuel back into car (has been making me money lately with the rocketing price of fuel--better than my savings account).
Look for propane/natural gas version of gensets if you have natural gas/propane available.