Question....

fireman00
fireman00 Registered Users Posts: 4
in Off Grid Solar & Battery Systems #1
Hello all!

Quick intro.... I live in NW NJ and had a 10.2 kw ground mounted array. The array is built with 51 panels, each one puts out 200 watts. There are three DC to AC inverters which feed into a single underground wire run for about 200 feet to the house where it was spliced into the main feed.

When I had the system installed 8 years ago I went with "grid tied" vs "battery bank" due to venting and cost concerns. For safety reasons, the system shuts down when the grid loses power.

At the present time I can't afford the 12 grand to hook my array up to a 12,000 watt hour battery bank system.

In the event of a long lasting power outage I’m looking for a way to utilize four of the panels to create a small battery bank system to provide power to a pellet stove and a couple of lights.

What are the thoughts if I shut down the array, remove 4 panels off the array, bring them to the back patio, attach them to the roof, connect them in serial then to a 30 amp solar charge controller connected to a lead battery of a 5 battery battery bank (12v deep cycle 200ah for ea battery). The battery bank would be connected to a 1100 watt inverter and to our pellet stove’s DC outlet. I’d have to ignite the pellets manually; but I’d avoid draining the batteries trying to run the stove’s igniter. The other 4 fans on the pellet stove are DC and according to Quadrafire the pellet stove would run for upwards of 8 to 12 hours depending on the battery used.

I would use the invert to power a couple of lights or the TV for several hours a day.

What are the obvious / not so obvious issues with my thinking.

Any thoughts/ comments would be appreciated.

Thanks in advance. Doug
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Comments

  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #2
    Re: Question....

    If you want it for backup purposes only, it doesn't have to be matched in size to the array. Doesn't even have to be related to the array. You can use a smaller bank which you always keep charged. If the grid goes down, you simply power your house from the inverter attached to this battery bank. After outage you recharge from the grid (that is from your GT inverters powering the grid).

    Although it is complicated, you probably can set it up so that one (or more) of your GT inverters would be able to provide power to charge batteries during long outages. Or you can replace one of your GT inverters with a hybrid inverter and solar charger.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: Question....

    Welcome to the forum Doug.

    Temporary reconfiguration of an array to provide charging for a small battery bank in the even of an outage is not impossible. It has and can be done. :D

    A couple of issues. You mention connecting four panels in series. Without knowing what Voltage the panels are you won't know what this results in. 200 Watt panels are likely "GT" panels with a Vmp around 30, so four in series would be 120 VDC. This would also be an 800 Watt array capable of about 50 Amps on a 12 Volt system. This is MPPT territory.

    Second, five 200 Amp hour 12 Volt batteries in parallel is a no-go. They won't remained balanced for long, and 50 Amps would not be sufficient for charging 1000 Amp hours of battery. Nor is it likely you would need that much.

    Last, you mention the pellet stove's DC outlet and say its fans are DC. Are you sure you don't mean AC? Inverters output AC, not DC. As such if it really is DC the inverter would not be needed.

    For inverter power (including the pellet stove run from standard AC) you should get a Kill-A-Watt and measure the power you would need in an emergency. For example you might want to keep the refrigerator running too. Once you have a number for Watt hours to provide and maximum Watts to supply it will be much easier to design your back-up system.

    BTW you will also need to keep whatever batteries you use charged while not in use, otherwise they will self-discharge to a state of 'dead'.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #4
    Re: Question....
    fireman00 wrote: »
    What are the thoughts if I shut down the array, remove 4 panels off the array, bring them to the back patio, attach them to the roof, connect them in serial then to a 30 amp solar charge controller connected to a lead battery of a 5 battery battery bank (12v deep cycle 200ah for ea battery). The battery bank would be connected to a 1100 watt inverter and to our pellet stove’s DC outlet.

    Welcome to the forum.
    Those five batteries will be a 1000 ah bank and would like to see about 1000 watts of solar power (after losses) if it is to be charged while the grid is out. It's not yet clear to me that you need that size bank.

    Whatever size bank you need, you should realize that most of the deep cycle batteries used in the residential renewable energy industry are NOT a good choice for a backup battery. Backup batteries spend most of their time floating and are seldom discharged. In order to have a long float life, their cycle life is compromised.

    Also, it is generally a mistake to have so many batteries in parallel. Batteries in parallel do not share current equally while cycling, and the more they cycle, the more they diverge in their capacity and lifespan. In a backup application, however, parallel batteries are not as much of a problem because there is not much cycling (but parallel batteries are still not the optimal arrangement).
    fireman00 wrote: »
    The other 4 fans on the pellet stove are DC and according to Quadrafire the pellet stove would run for upwards of 8 to 12 hours depending on the battery used.

    We need to get technical... how much do the fans draw? Are they on all the time? How many wattHours (or ampHours) per day? The answers will help to determine the correct battery bank size.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: Question....

    i'll go along with northguy's recommendation of just adding a psw inverter with charger and ac pass through ability and a battery bank. if the 1100w inverter you speak of is an exeltech then it does not have a charger built into it and you would then need to buy a 3 stage charger separately.

    i have a magnum mms 1012 for 1000va and with the remote (recommended) i can vary the charger up to 50a at 12va. the charger current is fixed without the remote. while utility ac is active it will pass through the inverter to the circuit it powers while similtaneously delivering a charge to the 12v batteries. once utility power fails a relay inside the inverter trips very quickly activating the inverter and without a scope it is not a noticeable transfer. at that point you operate from batteries through the inverter and off to the ac load. upon utility power returning it may take a few seconds for the inverter to sense good ac to it and then it trips the relay again to return to utility ac and will commence recharging the batteries again. it works very well, but at the 1000va max power it will not last very long without a huge battery bank and paralleling more than 2 batteries isn't recommended. other battery voltages are available, but the costs are way higher and often allow for a higher wattage that one may not need as you really are going for autonomy.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #6
    Re: Question....

    I think you can combine the ideas of everyone here, and figure out your absolute needs for a couple days of power failure and charge a battery bank capable of supplying those needs to a discharge of 50%. My guess is your stove will use more than any other item, so knowing what it draws will be paramount.

    Learn what it takes to charge the batteries and write it down. If it's 4 panels and a 30 amp MPPT charge controller, own one and if your very concerned, hook it up so your sure you have all the pieces.

    If you have a failure, your good for a couple days, and if it looks like it will last longer you can rewire the array. Batteries will have to maintained charged in some manner or they will rapidly die. So setting it up like this will give you some comfort and the ability to change in case for a major event.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • fireman00
    fireman00 Registered Users Posts: 4
    #7
    Re: Question....
    NorthGuy wrote: »
    If you want it for backup purposes only, it doesn't have to be matched in size to the array. Doesn't even have to be related to the array. You can use a smaller bank which you always keep charged. If the grid goes down, you simply power your house from the inverter attached to this battery bank. After outage you recharge from the grid (that is from your GT inverters powering the grid).

    Although it is complicated, you probably can set it up so that one (or more) of your GT inverters would be able to provide power to charge batteries during long outages. Or you can replace one of your GT inverters with a hybrid inverter and solar charger.

    excellent idea! I'm going to reach out to our solar installer about replacing one of the inverters with a hybrid inverter/ charger.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: Question....
    fireman00 wrote: »
    excellent idea! I'm going to reach out to our solar installer about replacing one of the inverters with a hybrid inverter/ charger.

    For which you will need:
    Hybrid inverter same size as existing GTI
    Battery bank sufficient to handle the AC ripple (100 Amp hours per 1kW of inverter on 48 Volt system)
    Charge controller capable of handling sufficient current to recharge battery bank
    Re-arrange array configuration to accommodate lower Voltage of charge controller (or very expensive XW 600 V MPPT 80 controller)
    Miscellaneous hardware and wire to facilitate change-over

    Five or six thousand dollars ought to do it. Not including labour.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #9
    Re: Question....
    Cariboocoot wrote: »
    Five or six thousand dollars ought to do it. Not including labour.

    I would say more than that.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: Question....
    NorthGuy wrote: »
    I would say more than that.

    Yeah, but we live in Canada. That's a 50% premium on everything! :p
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  • fireman00
    fireman00 Registered Users Posts: 4
    #11
    Re: Question....
    Cariboocoot wrote: »
    Welcome to the forum Doug.

    Temporary reconfiguration of an array to provide charging for a small battery bank in the even of an outage is not impossible. It has and can be done. :D

    A couple of issues. You mention connecting four panels in series. Without knowing what Voltage the panels are you won't know what this results in. 200 Watt panels are likely "GT" panels with a Vmp around 30, so four in series would be 120 VDC. This would also be an 800 Watt array capable of about 50 Amps on a 12 Volt system. This is MPPT territory.

    Second, five 200 Amp hour 12 Volt batteries in parallel is a no-go. They won't remained balanced for long, and 50 Amps would not be sufficient for charging 1000 Amp hours of battery. Nor is it likely you would need that much.

    Last, you mention the pellet stove's DC outlet and say its fans are DC. Are you sure you don't mean AC? Inverters output AC, not DC. As such if it really is DC the inverter would not be needed.

    For inverter power (including the pellet stove run from standard AC) you should get a Kill-A-Watt and measure the power you would need in an emergency. For example you might want to keep the refrigerator running too. Once you have a number for Watt hours to provide and maximum Watts to supply it will be much easier to design your back-up system.

    BTW you will also need to keep whatever batteries you use charged while not in use, otherwise they will self-discharge to a state of 'dead'.

    Thanks for the input!

    I'm in the process of reaching out to the installer to get more info on the panels and the inverters and will come back with more details on the array.

    The pellet stove is a "Quadrafire Mt. Vernon AE". The ignitor runs on AC, the remaining fans are all DC (plug for the stove - they are MUCH quieter than the original model which had AC motors.... VERY NOISY).

    I'd have the battery bank hooked to a trickle charger until needed.

    I have a 30 amp charge controller that I'd use to connect the panels to the battery bank but it's become obivious I need more informaiton on panel specs to avoid damaging components.

    I was thinking of a battery bank with the postive posts all connected to a single common postitive terminal post - using the same length of copper. Same with the negative side. Connect the inverter and stove to these single common terminals. I was thinking this would pull same amps from each battery keeping things balanced.
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  • fireman00
    fireman00 Registered Users Posts: 4
    #12
    Re: Question....
    niel wrote: »
    i'll go along with northguy's recommendation of just adding a psw inverter with charger and ac pass through ability and a battery bank. if the 1100w inverter you speak of is an exeltech then it does not have a charger built into it and you would then need to buy a 3 stage charger separately.

    i have a magnum mms 1012 for 1000va and with the remote (recommended) i can vary the charger up to 50a at 12va. the charger current is fixed without the remote. while utility ac is active it will pass through the inverter to the circuit it powers while similtaneously delivering a charge to the 12v batteries. once utility power fails a relay inside the inverter trips very quickly activating the inverter and without a scope it is not a noticeable transfer. at that point you operate from batteries through the inverter and off to the ac load. upon utility power returning it may take a few seconds for the inverter to sense good ac to it and then it trips the relay again to return to utility ac and will commence recharging the batteries again. it works very well, but at the 1000va max power it will not last very long without a huge battery bank and paralleling more than 2 batteries isn't recommended. other battery voltages are available, but the costs are way higher and often allow for a higher wattage that one may not need as you really are going for autonomy.

    I was looking at an AC coupled system from Backwoods solar which would run the entire house... but the cost, about 10,000 dollars, is prohibitive right now.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #13
    Re: Question....
    fireman00 wrote: »
    I was looking at an AC coupled system from Backwoods solar which would run the entire house... but the cost, about 10,000 dollars, is prohibitive right now.

    Time to reconsider what loads are really necessary in an emergency situation. Time to consider more energy efficient appliances etc. Time to consider what usage is really necessary and what is actually waste.
    As has so often been said by others when speaking of off grid systems: "Conserve, conserve, conserve."
    This doesn't mean doing without, it means cutting waste. It means what to many is a whole new way of thinking, a new mindset.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #14
    Re: Question....
    waynefromnscanada wrote: »
    ... a new mindset.

    I'd like a new mindset. Mine has got holes in it. :blush:
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #15
    Re: Question....

    that's ok coot as i've lost mine.:confused::p

    fireman00,
    as far as backing up a whole house, yes, it is quite expensive and not necessary in most cases. now you could use a bigger inverter that takes 24v or 48v battery banks if your necessary circuits are larger in scope than about the 1000w area. extra batteries and larger inverter would still be expensive, but should be well under 10 grand.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #16
    Re: Question....
    fireman00 wrote: »
    I was looking at an AC coupled system from Backwoods solar which would run the entire house... but the cost, about 10,000 dollars, is prohibitive right now.

    I don't think there's a cheap way to build a backup system. If the cost is a big concern, you may consider a generator. This will be cheaper anyway.
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