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Thread: Small off grid system help

  1. #1
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    Default Small off grid system help

    Hello,

    I'm new to solar but wanted to take a shot at setting up a system to run a small pond I have in my yard. The pond uses a 900GPH pump 120v 60w. It also has an air pump for a filter module 120v 15w.

    I'm considering using 2 Trojan 6V batteries (in a 12v configuration) rated at 390ah each. According to my math, that gets me about 100 hours of run time with fully charged batteries (60w +15w+ (some % of inverter loss = 100w ?)

    Can I use a small grid tied battery charger to continuously top off the batteries which would then run the inverter and pumps?

    From here, I wanted to add solar panels until I could untie the system. This would make it easier for me to purchase the panels over time.

    Are there any risks to this setup? I've looked at some Magnum MMS1012G inverters that charge via grid power but they seem very expensive ($1,000). Isn't it cheaper to just use a 5amp charger to top off?

    lastly, what solar panels would you suggest?

    Thanks,

    Fred

  2. #2
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    Yes but why?
    do the pumps run 24/7 or just part of the day.
    Use the calculator here to determine what you will need panel wise etc.
    http://www.solarpaneltalk.com/showth...Battery-Design
    Rich
    WWW.solarsaves.net

    NABCEP certified Technical Sales Professional

    http://www.solarpaneltalk.com/showth...Battery-Design

    http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

    www.gaisma.com

  3. #3
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    Quote Originally Posted by Naptown View Post
    Yes but why?
    do the pumps run 24/7 or just part of the day.
    Use the calculator here to determine what you will need panel wise etc.
    http://www.solarpaneltalk.com/showth...Battery-Design
    Yes, the pumps run 24/7 so I need some battery to support them in the evening. I'm trying to do this on a budget so my plan was to invest in an inverter and batteries. Hook up the inverter and run the pumps from this keeping the batteries topped off with a small amp charger. I hope to purchase some panels to support and eventually replace the battery charger so it's completely off grid.

  4. #4
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    Hint
    Save your money and run it off the grid power it will cost less by far in the long run.
    Rich
    WWW.solarsaves.net

    NABCEP certified Technical Sales Professional

    http://www.solarpaneltalk.com/showth...Battery-Design

    http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

    www.gaisma.com

  5. #5
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    Quote Originally Posted by Naptown View Post
    Hint
    Save your money and run it off the grid power it will cost less by far in the long run.
    Would you still suggest this if I paid 31 cents per kwh ?

  6. #6
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    Quote Originally Posted by fredlee View Post
    Would you still suggest this if I paid 31 cents per kwh ?
    I would suggest that if you were paying up to a dollar a KWH.
    batteries and inverters dont last that long and will eat you alive in costs that you will have to pay up front and in full.
    Rich
    WWW.solarsaves.net

    NABCEP certified Technical Sales Professional

    http://www.solarpaneltalk.com/showth...Battery-Design

    http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

    www.gaisma.com

  7. #7
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    Quote Originally Posted by Naptown View Post
    I would suggest that if you were paying up to a dollar a KWH.
    batteries and inverters dont last that long and will eat you alive in costs that you will have to pay up front and in full.
    Fred battery alone will cost you 60 cents per Kwh up front in cash. In 2 years you get to buy it again. That does not count all the other junk to charge the battery up and supply power to your pump. Do the math.
    MSEE, PE

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