OK now what.....

SystemSystem Posts: 2,511 admin
Well I've been on this solar kick for about 8 months. I've gone out and purchased some components online and locally, and I'm putting together some material as we speak (helps having friends that are electricians)

This is what I have so far:

4- 100W 'b' panels, +/- 7Amp
1-C60 with CM
6- 6V 220Ahr golf cart batteries
1- Ingersoll Rand 1800W inv (think Xantrex XM series)
1 Xantrex 1500 Xpower

80' #3AWG (panels are 25' away)
6x 25' #10AWG stranded (panels to combiner box)
250' 12/2 wire for ac side of Inverter to point of use outlets in house
1- 10' grounding rod

I built a sealed battery box and I'm venting it through a 1" pvc vent to the ridge vent in my attic (gas will find highest point right?)

I am ready to start wiring everything together, but I don't know where to find the optimal wiring configuration. Also, what am I missing from this list? I'm sure I need some sorts of fuses or breakers, (do I ? ) and how do I size them and where do they go?

Thanks in advance for any help you may have.

-Billy D

Comments

  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: OK now what.....

    Consider a voltage controlled battery box fan,,, like the Zephyr :http://www.zephyrvent.com/

    I use a simple voltage controller to turn the fan on at the gassing voltage. While hydrogen is lighter than air,, I am not sure I would trust a simple atmospheric vent to carry the gas away. (other might have a different opinion).

    You do need fuses from the between the battery and the controller,, and between the battery and the inverter, (or any other loads) at a minimum.

    Icarus
  • snuffysnuffy Solar Expert Posts: 72 ✭✭✭✭
    Re: OK now what.....

    A disconnect/breaker between the battery bank and the inverter, disconnect/breakers between the solar panels and charge controller, disconnect /breaker between the charge controller and battery bank. Some large cable to go from battery bank to inverter, 2/0 or 4/0 possibly. Connectors for these cables. Possibly some buss bars to connect the battery bank to.
  • BB.BB. Super Moderators, Administrators Posts: 32,027 admin
    Re: OK now what.....

    Generally, you want the battery box to circulate air through it... Not just build up hydrogen and oxygen gasses to an explosive level...

    To do that, you probably need much larger than a single 1" pvc pipe to the roof.

    I would probably go with 3-4" diameter pipe, plus you should have an inlet into the box (roughly the same size as the outlet) to allow air to circulate... Right now, all you are really doing is "venting pressure"... The gasses can accumulate very easily. Adding a fan may be important if you cannot improve natural air circulation (1" is not enough in any case).

    Another question--you have 400 watts of solar panels and over 3kW of inverters... At best, you can, roughly expect around 1,000-1,100 Whrs (1-1.1 kWhr) of power per day for ~6 months of the year.

    If you were to run those two inverters at full tilt--that would be about 20 minutes of 3kW load per day.

    And with all of those batteries:

    ~3x220AH=660 Amp*Hours at 12 volts

    400 watts of solar panels / 17 volts = 23.5 amps @ 12 volt battery bank

    23.5/660 = 3.6% of charge current (of 20 Hour rating for your battery bank).

    Basically, you have too small of solar panels for the battery bank--and may have too large of inverters (or expect too much from your solar panels) with what you have now...

    If you have AC grid power and/or a generator to charge the bank every couple of days of use--it may still meet your needs.

    But, otherwise, the use of your system is a bit confusing to me right now.

    Regarding fusing/breakers--yes, you will want a major breaker/fuse between the battery / bus bar common point and the "branch circuits"...

    A 1.8 kW inverter would draw:

    1,800 watt * 1/0.85 inv eff * 1/10.5 volts batt min = ~202 amps maximum

    So, the circuit should be 1.25x larger (per NEC recommendations) than the maximum expected operating current:

    202*1.25 = ~250 amps (wire size and minimum fuse/breaker rating)

    You can go through our host's web store and see what wiring and fusing/breakers would work best for your application. Remember, the longer the wires, the more voltage drop--and the larger (more oversized in AWG) that you will need.

    Passing several hundred amps around at 12 vdc is a bit of a pain... One reason we recommend that people use a higher voltage (24/48 vdc) battery bank--so the wiring/fusing can be a more reasonable size.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: OK now what.....

    safety......just as I suspected.

    Does anyone know where I can go online to get a wiring diagram of how this should be wired up.

    other questions i have are like......

    ok #3 AWG from panel to battery, what about the controller, #3 too? how about battery to inverter, same? disconnects have to be sized to controller...60Amp?

    I feel like I'm going in too many directions at once....
  • System2System2 Posts: 6,290 admin
    Re: OK now what.....
    BB. wrote: »

    Basically, you have too small of solar panels for the battery bank--and may have too large of inverters (or expect too much from your solar panels) with what you have now...

    If you have AC grid power and/or a generator to charge the bank every couple of days of use--it may still meet your needs.

    But, otherwise, the use of your system is a bit confusing to me right now.



    -Bill

    Thanks Bill, this site has proved to be the most helpful one I've found so far.

    As for my useage, I live in Florida and this will serve as a seperate back up system should I lose power after another hurricane. Inbetween storms, I'd like to utilize what I've created to knock down my electric bill a bit. The size of my inverters are a bit larger than I need right now, but I hope to grow into them. Remember, I do live in South Florida and get just about as many clear sunny days as anybody.

    With this in mind, what appliances can I afford to run on a system with this configuration. I'd like to get my refrigerator and my home office off the grid......am I reaching? What would be a realistic draw?

    -Billy D
  • snuffysnuffy Solar Expert Posts: 72 ✭✭✭✭
    Re: OK now what.....

    I purchased one of these books and it helped me a lot.

    http://www.amazon.com/Photovoltaics-Installation-Solar-Energy-International/dp/0865715203
  • BB.BB. Super Moderators, Administrators Posts: 32,027 admin
    Re: OK now what.....

    You can use this site to estimate your available solar power based on where you live... Choose a site that is near you, or has reasonably similar weather patterns (for example coastal influences).

    Enter in 1kW (minimum size, choose for easy scaling later). And a derating of 0.52 (using inverters and flooded cell batteries). Defaults for the rest of the information for now.

    Example of Daytona Beach:
    Results for 1kW of solar panels @ 52% sys eff
    
    Month
    Solar Radiation (kWh/m2/day)
    AC Energy (kWh)
    Energy Value ($ at $0.09 per kWhr)
    
    1      4.35          97        8.73   
    2      4.96          102        9.18   
    3      5.81          130        11.70   
    4      6.14          129        11.61   
    5      5.98          128        11.52   
    6      5.67          116        10.44   
    7      5.74          122        10.98   
    8      5.65          121        10.89   
    9      5.51          114        10.26   
    10      4.84          105        9.45   
    11      4.67          100        9.00   
    12      4.23          95        8.55   
    =======================================
    Year=5.30 hrsofsun 1,359 kWhrs/yr $122.31 worth of power
    

    So, toss out the bottom three months, Feb is 102 kWhrs per month... Or:

    102kWh/30day = 3.4 kWhrs per day for 1 kW of solar panels

    But, you have 400 watts of solar panels, so multiply everything by 0.4x (400 watts / 1,000 watt):

    3.4 * 0.4 = 1.36 kWhrs per day (average min for 9 months of the year)...

    Now, how much can you power at your home with 1.36 kWhrs of power? Perhaps one EnergyStar fridge/freezer Rated under 496 kWhrs per year.

    Your better bet would be to use a Kill-A-Watt meter to measure your planned loads--plus, this is a great tool for measuring your power usage throughout your home (to start your conservation regime).

    wind-sun_2044_9106Kill-A-Watt AC Power Monitor Meter
    P4400 Cumulative Killowatt-Hour Monitor

    Because your solar panels are so small right now--you will probably need a good 60 amp battery charger that can equalize your bank around once per month.


    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,363 ✭✭✭✭✭
    Re: OK now what.....
    I built a sealed battery box and I'm venting it
    through a 1" pvc vent to the ridge vent in my attic
    (gas will find highest point right?)


    1) hydrogen will "float" to the higher level. Generally, "pure" gas (like the oxygen that also vents) is heavier, and will sink.
    1" is not enough, 3" should not even need a fan, unless it's to reduce heat build-up.

    2) safety is over-rated - unless you are this fellow who got a shirt sleeve snagged in his lathe. (don't click if you are squeamish)
    - edit - link too bloody to post email me for it. -
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • System2System2 Posts: 6,290 admin
    Re: OK now what.....
    BB. wrote: »

    Your better bet would be to use a Kill-A-Watt meter to measure your planned loads--plus, this is a great tool for measuring your power usage throughout your home (to start your conservation regime).

    wind-sun_2044_9106Kill-A-Watt AC Power Monitor Meter
    P4400 Cumulative Killowatt-Hour Monitor

    Because your solar panels are so small right now--you will probably need a good 60 amp battery charger that can equalize your bank around once per month.


    -Bill

    I just got my kill a watt in the mail yesterday and have been playing with it all day. you think my next investment is in more panels then?
  • System2System2 Posts: 6,290 admin
    Re: OK now what.....
    BB. wrote: »
    Because your solar panels are so small right now--you will probably need a good 60 amp battery charger that can equalize your bank around once per month.


    -Bill

    To save myself the expense of a battery charger, could I simply disconnect my load from the inverter and plug them into FPL when needed then just let my batteries fully charge before switching back outlets? This is primarly an offgrid back up generator.

    -BillyD
  • mike95490mike95490 Solar Expert Posts: 9,363 ✭✭✭✭✭
    Re: OK now what.....
    I just got my kill a watt in the mail yesterday and have been playing with it all day. you think my next investment is in more panels then?

    Or at least a good charger to get the batteries topped off before they sulphate.


    wireing schematic
    There is some explanation here, about battery wires, on the diagonal -
    http://www.smartgauge.co.uk/batt_con.html

    There is a nasty compressed JPG of someones schematic here:
    http://www.offgrid-desert-living.com/solar-schematic.html
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators, Administrators Posts: 32,027 admin
    Re: OK now what.....

    TGO,

    Hmmm... Usually, there is a minimum charging current required to properly equalize flooded cell batteries... Typical charger ratings are 5% to 13% of the 20 Hour rate (your bank, 660 Amp*Hours at 12 volts).

    The problem is that the acid/electrolyte can stratify in fixed batteries (no motion like in a vehicle)--and the 5% is the usual rule of thumb minimum to properly "stir" the electrolyte... In theory, you could also use a ~20 amp charger plus you 25 amp solar panels--added together should be enough current to mix.

    For long battery life--you need to not let the batteries fall below ~75% state of charge for more than a hand full of hours... The sulfates begin to harden and the battery bank will begin its slide downhill in capacity.

    The two best ways to know your bank's state of charge--A hydrometer (plus thermometer), or a battery Monitor.

    You can also use an accurate volt meter to estimate the level in charge by using a DVM--but the batteries have to rest for 3 hours or so (no charge or discharge) to properly estimate the charge level.

    A hydrometer is accurate, cheap, and relatively easy--but messy. Usually, after you know the state of the entire bank, you just check one cell (pilot cell) for a quick reading.

    However, the Battery Monitor is the way to go--it is the equivalent of the gas gauge for your fuel tank... Imagine driving around without a fuel gauge or an odometer... A Battery Monitor will probably save you your first battery bank from an early life failure due to undercharging/over discharging.

    Here are some links:

    Deep Cycle Battery FAQ

    wind-sun_2044_2146928Freas HD98C Precision Hydrometer Set


    Battery Monitors (Trimetric for low cost, Xantrex LinkLite/LinkPro for higher end)

    And, for an emergency off grid system--especially if it will be used for 9 month of the year running your appliances--I would really push a TSW (True Sine Wave) Inverter for your installation. You probably would need a minimum of 1,000 watt inverter to run a fridge (starting motor, running auto defrosters).

    If you have heavy loads that run part time (tools, well pump), then you can save the MSW (Modified Square/Sine Wave) Inverters for those applications.

    Depending on what you do for the TSW Inverter--some include both an internal transfer switch and an AC Mains powered battery charger. Basically, you are building your own extra-large UPS for your emergency home circuits (fridge, lights, radio). And you can still connect your solar panels to your battery bank.

    Would I suggest more solar panels--probably--but this is really in your hands... What do you want from the system, and what do you want to pay.

    You are right in the middle of where solar systems are hard to justify cost wise...

    A simple Grid Tied Inverter system... Cheapest and when connected with net metering--the best return on your solar dollar (all available power is sent to the home/grid).

    An off-grid system (like you are building)--if it is always in standby--you have "wasted" your solar panels except the few weeks a year you need them for emergency power.

    And if you try to run your fridge and a few lights off of your off-grid system--you have to keep an eye on the battery charge levels (to prevent battery bank damage), and you are cycling the batteries and using an extra inverter--which is inefficient and reduces the life of the batteries (through normal charge/discharge cycling).

    Lastly, there is a beautiful system from Xantrex (and a few others) that combine the Grid-Tied operation of cheap and efficient with the ability to run off-grid in an emergency with solar panels + generator + other power sources. These Hybrid systems do a pretty nice job of bridging the Off-Grid / GT gap... But they are not cheap and you will still have battery maintenance/replacement (should not be as often as a "off-grid" that is used every day).

    What is best for you--don't know... For me--I ended up with the Grid Tied system and a small gasoline Genset (Honda eu2000i).

    1. We don't get many power failures at all--and the last multi-day failure in our area was over 50 years ago.

    2. I went through my home and did as much conservation as I could (or at least was thinking about before joining this forum) and reduced my power needs where a small 1,600 watt generator and 20 gallons of stabilized fuel (plus a siphon hose for my car) will keep enough power for running my fridge + freezer + a few lights for several week.

    But I don't live in a severe weather area (cold or heat)... Your decisions will probably be different than mine.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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