1250watts of solar panels given to me for free, want to make offgrid setup.

[fastfwd]

Hi,

I was given 1250 watts of panels (6 x 250watt) for free. All have been tested and working optimally.

i wish to make a off grid setup coinciding my on grid setup with the free panels given to combat power prices at my house in Australia.

I have a server room and an adjacent wall with my kitchen fridge which the two together have been tested over 24 hours and use 175watts of power on average.

I wish to make this offgrid setup power this 24/7 as a start. The calculations im completing is based on 200watts of usage over 24 hours on 240volts = 4800watt/hours.

Looking at purchasing a semi budget sinewave inverter with charge controller inbuilt like this: http://www.ebay.com.au/itm/HSE-2400W...EAAOSwRgJXjvMV

and some quality deep cycle batteries such as these: http://www.aussiebatteries.com.au/ba...eep-cycle-agm/

The plan is i want the system to pay itself off in 2 years. I believe it will have a savings of $400-600 per year on my electricity bills so im basing the budget off this build at $800-1200

I know there is quite a few variables that can effect the setup without knowing exact details such as sun time on my panels and weather situations where i live. But i live in an area with over 12 hours of sun and solar panels will have 7-10 hours of direct sunlight.

I need to find out how much battery AH i will need for this setup and if its viable for my budget. And/or if you have any other suggestions about my build i can change. Any info will be much appreciated.

[fastfwd]

Worse case if what im trying to achieve is going to be to costly and replacement cost of batteries over 5-10 years is not worth the end goal. I would like to setup the same system to power my external house lighting (gardens lights etc) for 5-6 hours per night on a timer using about 100watts so 500-600watt hours total.

[Mike90250]

175w x 1.5 (eff losses) x 24 hr= 6300 consumed / harvest /stored per day
With a 48V battery bank, that can be done with 2 banks of 48V golf cart batteries. Not sure I'd advise you to try this first with expensive AGM batteries.
This will cost you money every day, When using batteries, the replacement cost will always be much more than grid power.

The way to save money is to simply use PV panels and a Grid Tie inverter, to unwind your electric meter. Skip the thousands of $$$ for battery cost and the hours wondering if you got it right. It does require a permit from the city and approval from the Utility to backfeed their grid.

[fastfwd]

175w x 1.5 (eff losses) x 24 hr= 6300 consumed / harvest /stored per day
With a 48V battery bank, that can be done with 2 banks of 48V golf cart batteries. Not sure I'd advise you to try this first with expensive AGM batteries.
This will cost you money every day, When using batteries, the replacement cost will always be much more than grid power.

The way to save money is to simply use PV panels and a Grid Tie inverter, to unwind your electric meter. Skip the thousands of $$$ for battery cost and the hours wondering if you got it right. It does require a permit from the city and approval from the Utility to backfeed their grid.

Mike.

unfortunately here in australia. Specifically western australia we pay 11c per unit (Amp hour) off peak times and 26c per unit on peak times. When we use panels here to tie back into the grid the power companies only give us 4c per unit back. So we literally get bent over and shafted royally.

This is the reason why i want to offgrid, purely so i can keep 100% of the power i make. rather than waste half of it going back to the power companys pockets.

Side note and ive tried this in the past but users on here dont like the idea. I have 100s of 12v 5.5AH batteries from UPS's. Literally 100s of them. All of them in 80-90% working order. Its tough with these batteries...to try and make a 12 or 24v or even 48v battery bank setup it accumulates fast and anything past 10 batteries can be a little unsafe.

i have 8 of these in a bank atm on 1 solar panel with a 12v charge controller running some outdoor lights for a little fun project but looking for something more permanent.

[SunEagle]

I don't see how you are going to keep your budget to $1200 when you look at the cost of a battery system and inverter that needs to provide over 4kWh a day.

You can do the math yourself. That inverter is over $400 so how much will $800 get you in a battery system to delivery 4kWh a day without going below even 60% SOC?

Now if you don't plan on the system paying for itself in a few years you could build one that will work but once you include batteries I don't see any type of payback even if your POCO is charging you 26c per unit cost for electricity.

Most calculations show a battery system will deliver XXX kWh over it's lifetime (provided it is not discharged below X %) and based on the price to purchase and ship the cost comes to approximately 50c per kWh.

[Sunking]

Even with high grid power cost is still a lot less expensive than batteries. You are just asking for even higher prices going off grid. Not logical.

[organic farmer]

Our 48vdc 600ah battery-bank cost us around $2600USD including cables and terminals.

[bcroe]

A battery system is for when there is no other way; grid power is most times many times cheaper than battery power, and doesn't have
a list of other issues. If you could manage to use the power from the solar array as it is generated, you don't lose on the in/out differential
of your grid tie. Bruce Roe

[jflorey2]

unfortunately here in australia. Specifically western australia we pay 11c per unit (Amp hour) off peak times and 26c per unit on peak times. When we use panels here to tie back into the grid the power companies only give us 4c per unit back.

Getting paid 4 cents/kwhr sounds a whole lot better to me than paying 11 or 26 cents per kwhr.

So we literally get bent over and shafted royally.

I knew you guys were into some odd stuff down under there .. . .

This is the reason why i want to offgrid, purely so i can keep 100% of the power i make. rather than waste half of it going back to the power companys pockets.

As long as you are willing to pay ~50c per kwhr to do that, you can. Doesn't make any financial sense though.

[organic farmer]

A battery system is for when there is no other way; grid power is most times many times cheaper than battery power, and doesn't have a list of other issues. If you could manage to use the power from the solar array as it is generated, you don't lose on the in/out differential of your grid tie. Bruce Roe

I have access to grid power, but it is terribly unreliable.

Obviously grid power is cheaper. If cost is your only consideration than stay on grid [for days when the grid is up].

[Sunking]

Getting paid 4 cents/kwhr sounds a whole lot better to me than paying 11 or 26 cents per kwhr.

As long as you are willing to pay ~50c per kwhr to do that, you can. Doesn't make any financial sense though.

Ditto, fools and their money will soon part ways.

[Sunking]

Our 48vdc 600ah battery-bank cost us around $2600USD including cables and terminals.

Must be used car batteries at less than $90/Kwh.

[Logan5]

but they look brand new.

[Mike90250]

This is the reason why i want to offgrid, purely so i can keep 100% of the power i make. rather than waste half of it going back to the power companys pockets.

Then you only make the array large enough to zero out your daytime usage and forget trying to make $ selling it back. If you need 2Kw of generation to cover peak hours, install 4K of panels and you have shaved your 26c to zero.
Do you have a spreadsheet (excel?) plug the numbers in, your daylight hours, your peak hours and massage it around till you find the sweet spot. Or just jump in and stack up a lot of batteries and fuses. Used AGM batteries - use lots of fuses or breakers to be fire safe for when one battery fails and the 6 others try to dump their power into it. Boom

[SunEagle]

I have access to grid power, but it is terribly unreliable.

Obviously grid power is cheaper. If cost is your only consideration than stay on grid [for days when the grid is up].

I meant to ask you how did you make out with all that white stuff that came down a week or so ago. It looked like New England got hammered.