grid tie with battery backup

[sirmoiu]

Hi everyone, I have a question that I hope that can be answered, when is the best or energy efficient time to go on your battery, during day while the batteries are charging or at night. Thanks

[Robin]

What is the intent? do you want to reduce your electricity bill by running on batteries?
If so, it is usually hard to beat the power company's prices. Replacing batteries is expensive. In either case, if you want to run off of batteries, you will need to shut down when the batteries reach a certain level. That level is usually adjustable. If you have a grid tie battery based inverter, you will be selling back all you can during the day. The batteries are charged. If you take the house or part of it off grid at night, you will have to wait the next morning until the batteries are charged again. These inverters cannot invert to run your house and charge at the same time. You have to make a choice.
Again, what is your goal?

[sirmoiu]

My intention is to reduce my power bill, and yes I have two 2kw grid tie battery base inverters that automatically switches between on grid and off grid, it switches to grid tie when the batteries reaches 45 per cent, and when sun rises it switches over to off grid, it can also be manually switched over, and we do not sell power back to the power company here in the Bahamas, our power consumption is reduced.

[Westbranch]

Just to clarify that is 45% SoC under load...  can you tell us what the loads are? and what the battery rating is?

[sirmoiu]

Ok, I have 10-150w panels total 1500kw, the 45 per cent is the battery voltage, the batteries are 4-200 ah 12 volts connected in series 48 volts total, the inverters are 2kw each. I hope that helps.

[phonetic]

Keep in mind battery cycle costs 10-20 cents per kWh, its really not cost effective to use nitetime tariff to charge batteries. for using power during day ?

[sirmoiu]

Thanks everyone for the good suggestions

[ananthapriya]

Oh god! how do i answer this question hmm yeah mostly for  Until now, gridtie solar power systems operated only when utility power was available. When the grid went down, the electricity from your solar panels was not used. Now, specialized inverters from Outback Power enable your gridtied solar panels to charge a battery bank from which you can power your home.and also  When the grid is running properly, your home or business will use power generated from your solar panels or pull electricity from the grid. Any excess power generated over and above your needs go back to your utility company for credits on your power bill in areas where net-metering is available.
!!!!!!!!!!!!!!!!!!!!!!This is the fact! you got your answer.

[Halfcrazy]

Actually battery based grid tie has been around for a good long time and Trace Engineering has been doing it for many many years. Outback is just one of the many manufacturers to make a battery based grid tie inverter. SMA and Schneider are a couple more.

Take a look here: http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=30&productCatName=Inverter%20Systems,%20Pre%20Wired%20-%20Grid%20Tie%20with%20Battery%20Backup

Ryan

[mtdoc]

Ryan,

Why did you discontinue the prewired Outback epanels?

[vtmaps]

Why did you discontinue the prewired Outback epanels?

I would also like to know.  I have recommended them to several newbies over at the NAWS forum, as well as to friends here in Vermont.

BTW, the June/July issue of Home Power has a Midnite advertisement for prewired Outback systems.

--vtMaps