"the reason I did not minded about sizing was because I rode that if I am going to be off grid and count with a generator, then the size of the bank does not necessarily need to be precisely calculated."
Jorge:
Getting by with a smaller battery bank because you have a generator, is a false economy in my book. You can do it, but you are going to pay for it in a shorter battery life.
Battery life is directly related to how deeply you cycle it. As an example, look at
http://store.altenergystore.com/mmsolar/others/USB_AVG_Life_Cycle_Graph.pdfWith a 20% DOD (depth of discharge0, it will survive about 2800 cycles. 30%DOD will drop it to 1800 cycles. At 50% DOD, 1050 cycles. At 80% DOD, you are down to about 550 cycles.
While the total number of cycles may vary between batteries, the percentage drop in the cycles is quite typical for all flooded lead acid batteries.
So, would you want your battery to last 2800 cycles (over 7.5 years) or 550 cycles (about 1.5 years) ? Personally, I would shoot for a 20% DOD on a daily basis, with no more than a 50% DOD in an emergency basis. With a generator, you can eliminate the reserve capacity that a stand alone solar system would need for cloudy days. But in going below that point, the greater your DOD, the shorter your battery life will be.
I would suggest that you attempt to quantify your loads, to properly size your battery bank. There is a load calculator at
http://store.altenergystore.com/calculators/load_calculator/Or you can make your own spreadsheet.
While a bit time consuming, it will be worth it in the long run. A side benefit is that it will point out the loads that either need reduction, or would be the easiest to reduce through conservation measures.
I think you should plan on using less expensive batteries such as T105’s (or equivalent) which typically have a 2-6 yr life. Or possibly L-16s, which typically yield a 4-8 yr life, for your next battery. Either would be less expensive to replace, if you do shorten the life of it. After you have learned to prolong the battery life, then you can move up to the forklift or other premium batteries.
I would recommend that you use a battery temperature sensor in conjunction with your charge controller and with your generator driven battery charger. I would also give some consideration to jumping your battery bank to 24V at this time. It would help with your wire sizing and reduce the number of charge controllers that you will need.
I would also recommend that you start with all brand new batteries. Depending on how far you have discharged them, you may have already used 25% (or more) of their cycle life. Putting them into a battery bank with new batteries, they will shorten the life of the new batteries to about the same level. Best to sell them to someone looking for a bargain, and get a fresh start.
You didn’t say what your inverter is. If it doesn’t have good load control features, I would consider installing a load controller between the inverter and the batteries.
Ken
