Trying to figure Battery Bank

[jkhale]

Hi all, I am trying to figure how many KWH's my Battery bank needs to be to run my home at current usage. Last year I used 7382 KWH at home. If my math is correct that is about 20.50 KWH per day using a 30 day month. Now if I wanted to store enough power for 2 days and not taking the Battery Bank any lower then say 60% how many KWH's do I need. I also need to figure out how long it will take to charge the system using 720 watts of panels at 12 volts. I am still unsure if it would be better to use a 12 volt system or switch to 24 volts.

Thanks for the help
Jack

[SunEagle]

Hi all, I am trying to figure how many KWH's my Battery bank needs to be to run my home at current usage. Last year I used 7382 KWH at home. If my math is correct that is about 20.50 KWH per day using a 30 day month. Now if I wanted to store enough power for 2 days and not taking the Battery Bank any lower then say 60% how many KWH's do I need. I also need to figure out how long it will take to charge the system using 720 watts of panels at 12 volts. I am still unsure if it would be better to use a 12 volt system or switch to 24 volts.

Thanks for the help
Jack

Simple answer is that it will cost you tens of thousands of dollars for a battery system to meet your power needs.

At 21 kwh per day you will need more than 7000 watts of panels and over 2000 AH 48volt battery system.

There is a great post in the off grid part of this forum that will help you understand how to size a system for your needs.

http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design

Go read that first and then think about why you want to spend 10 times what it would cost you to get power from the Utility grid.

[Naptown]

You don't even want to know the answer to that question.
But to start it would take a 100Kw battery bank.
12v would be a huge mistake this needs to be 48v at minimum
At 48v it will take 24 2v 2400ah batteries
A minimum of 10kw of solar
Multiple inverters and charge controllers and a generator for cloudy weather

[jkhale]

You don't even want to know the answer to that question.
But to start it would take a 100Kw battery bank.
12v would be a huge mistake this needs to be 48v at minimum
At 48v it will take 24 2v 2400ah batteries
A minimum of 10kw of solar
Multiple inverters and charge controllers and a generator for cloudy weather

Thanks Guys for the input.

[Sunking]

I will tell you exactly what it takes. A 6000 pound $24,000 battery you replace every 5 years and have all kinds of fun with the EPA and local fire Department to play with and inspect yearly to make sure you have proper spill containment, and an operating FM-200 system.

Any questions?

[Naptown]

I will tell you exactly what it takes. A 6000 pound $24,000 battery you replace every 5 years and have all kinds of fun with the EPA and local fire Department to play with and inspect yearly to make sure you have proper spill containment, and an operating FM-200 system.

Any questions?

Actually closer to 7000 pounds and $28000 for batteries
And the fun starts there

[Mike90250]

...If my math is correct that is about 20.50 KWH per day using a 30 day month. ....

I think you need to look at some serious conservation measures. Insulate, swap power sucking appliances for Energy Star versions.... that sort of thing, get your daily power usage down to
something affordable - 6KWh in winter should be doable, with no electric heating gear.
Mike

[jkhale]

I think you need to look at some serious conservation measures. Insulate, swap power sucking appliances for Energy Star versions.... that sort of thing, get your daily power usage down to
something affordable - 6KWh in winter should be doable, with no electric heating gear.
Mike

Hi Mike, I would love to get it down that low (6KWh). 8 Months out of the year we average about 12.33KWh per day. During the Summer with the Central Air it jumps as high as 47KWh during June,July,Aug and Sept. OUCH. Plus the fact that I live in a 100 year old home with a stone foundation and using 1/2 new wire and 1/2 old NTube. A/C is only about 10 years old. I did put in all new windows last Summer which did help. We use Gas Heat and Drier and Water. I really need to look into other ways I can Insulate.

Thanks for the input.
Jack

[russ]

Look into sealing air leaks - around doors, windows, electric switches and plugs, air ducts etc.