cocooners might also think twice about the added cost of using a 48/24/12 vdc system. with an inverter like the sunny island, you will be required to have batteries. furthermore, since it's not grid-tie, you will not get the benefit of net metering, which means you'll need to store all the excess power generated during the day otherwise you've wasting your investment in the array.
One of the reasons I like the www.xantrex.com/ inverters. They do (a few of them) priority powering. You configure it HOW you want it to power things, and it will take your solar power, shove it into batteries first, then to the grid (if you so chose). Or, it can power the batteries from the panels, and supplement charging from the grid (if having a blackout is a large concern to you).
If the grid is out, you are isolated from the grid (UL 1741 was it?). "No Islanding". As was said, you can't inject power into the grid when there is no power from the grid. By being isolated, then you run off of batteries.
make sure you have enough capacity so you don't run the batteries down too low every night otherwise their lifespan decreases (50%?). don't forget to check the water levels of the batteries every 3 months and clean the battery terminals. is it cold where you live? then your batteries won't be as efficient and you'll need to add more to compensate or pay extra to heat their environment. expect to replace batteries 3-6 times during the life of your solar panels. hopefully you'll have an easy time dumping 4,8,12 etc batteries at a time in some abandoned field. did one battery die? expect to replace the whole bank. figure on paying an extra 10-30 cents/kwh over the life of the battery.
If you live in a cold area, you would generally keep the batteries in the basement. So, the temperature based lifespan thing doesn't "count". You don't end up checking the water levels, as you would use deep cycle batteries, do not get as effected as the "car" batteries you are referring to ("car" batteries are the only ones I am aware of that are hurt by a deep cycle). Expecting to replace the batteries. I do not have solid numbers, however, most of the better units do a charging that is similar to how a
Batterminder works. As such, they last a LOT longer then you are indicating. I've had batteries (2 of them to be exact), where they were ready to be disposed of (wouldn't hold a charge for longer then 3 hours).
I ran it on my battery minder and now, 4 years later the thing can almost hold a charge thoughout the Winter. Empirically, I determined this as it's been 4 years since I ran it on the battery minder. I forgot to plug the battery (from my lawn mower) into the battery minder for Winter. The battery still had enough go to start my mower, 4 months into Winter. It struggled, and had to REALLY crank the mower (probably the oil had thickened too much), but it did start. Again, this was a battery that couldn't hold a charge for more then 3 or so hours. I determined that number by, one day I charged the battery up to mow the lawn. I disconnected the battery from the charger and was about the start the mower. Instead, I went to the store with the family, when I came back...it was about 3 or so hours. This was pre-owning a battery minder. The battery was not able to turn the motor over.
Why would you just "dump" the batteries in a field? Most places around where I live will take them for free, as they process them to get the lead out. They actually make a profit from that.
If one battery died...why would you need to replace the whole bank? I would replace that one battery. Seems a little simple...am I missing why you said that? Where did you get the pay an extra 30cents/kwh over the life of the battery?
I guess I'm missing something here.
). it would appear that wiring panels serially is the standard way of doing so for grid-tie systems...world-wide.
