Photowhit ✭✭✭✭

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Photowhit
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  • Re: Battery sizing for 600W panels

    So calculate your loads, we can't do this.

    Then figure how much charging you will get from your panels, 600 watts using a PWM charge controller, will yield differently depending on the VMP. many of today's 100 watt panels have a vmp of 18.9 volts. So 600 watts would yield about 30 amps IMP and a bit less in real world numbers. say 25 amps to be safe, should support about 250 amphour battery bank at 10%, I'd just use 2 golf cart batteries. 

    With daily cycling I like to use the 10% charging rate as a minimum. if you are in a particularly sunny area, say the Southwest US, you could support 4 6 volt batteries, but in areas with multiple cloudy days, I likely wouldn't try it.
  • Re: solar powered generator

    Hi Earl, and welcome!

    In general, off grid solar will be more expensive that the grid, so long as saving money isn't your goal if you have the grid near by, let's talk!

    Lots of old threads to read through with good advice.

    An off grid solar system involves several parts, a solar array of panels that change the sun's rays to electrical energy, a battery to store the energy, a charge controller to regulate the battery charging, and usually an inverter to make the DC energy in the battery into AC energy for home use.

    Without knowing exactly how much energy you will be using, and where you live and your willingness to use alternate means to charge the batteries during periods of cloudy days. It's hard to give a good idea of needs and costs. So anything would be a crapshoot. 

    A new modern fridge will use about 1 - 1.5 Kwh's of energy each day and will likely use more energy than anything else you have specified. Calculations on a system just to run the fridge, might look like this; 1.5 Kwhs of electric needed each day, 2 days autonomy (days with no solar charging before you run a generator) charging when the battery reaches 50% to lengthen the battery life. 1.5 Kwhs x 2 = 3 Kwhs x 2 (50% charging) = 6 Kwh battery bank.  Something like 4 Trojan T105golf cart batteries at 230 amp hours at 6 volts = 1380 watts or 1.38 kwhs will get you close.

    A single string of 4 batteries to lessen voltage drop, and you have a 24 volt system. To charge a 230 amp battery bank you will want an array that will provide 10-13% of the battery bank capacity if used on a daily basis (you can use 5-6% of this would be a weekend cabin without loads during the week) So 23-30 amps delivered to the battery bank in bulk charging at 24 volt nominal system voltage. This would seem to indicate 28 volts (charging voltage for a 24 volts system) at 30 amps or 28x30=840 watt array. but solar panels are rated in ideal conditions, they usually only produce 75% of their rated value so it works out to be around 1120 watts needed. 

    If you went with 72 cell panels you could use a cheaper PWM charge controller, They produce about 35 volts VMP which is high enough to effectively charge a 24 volt bank with some minimal losses. If you go with 60 cell panels you would need a MPPT type charge controller to use them effectively to charge a 24 volt battery bank, you would also receive about 10% more charging current if used with 72 cell panels but the cost difference is substantial between the 2 different types of charge controllers.

    Lastly an inverter, Something large enough to kick off a fridge which has a compressor. While the fridge will only use 100- 160 watts running (generally) it might take 5-10 times that wattage to start. Usually the minimal inverter I would recommend to run a fridge would be around a 1000 watts.

    Throw in some fuses/breakers, a combiner box perhaps for the panels...

  • Re: How to add onto my solar array

    Small wind often comes with a charge controller. You would typically not want wind and solar on the same charge controller. wind will usually need a diversion load, you can't 'turn off' a wind generator like you can with a solar array. That said you will want a charge controller which can handle a diversion load. I think Schneider/Xantrex C40 can as well as Morning start TS45 and TS60 in PWM controllers.
  • Re: 3 months no grid power, you all saved me

    That's awesome, Glad to hear!
  • Re: String size question

    Since you have repeated this, the math works out that voltages add but the amperage remains the same when solar panels are in series. If the panels are in parallel, the voltage remains the same and the amperage adds up...

    So if you want a 48 volt system(battery bank) you would need 2 panels in series to reach the proper charging voltage for an MPPT type charge controller and you might not be able to run 3 in series due to the VOC being to high in your climate, since the Flexmax is limited to 150 volts, I think it can handle a bit more without production, but please verify that if you want to try strings of 3. I think you can have 12 panels on 1 charge controller and 10 on the other if you want/have 22 panels. 12 panels will be slightly over there suggested 4000 watt max, but there will be very little loss and only in the coldest of days.

    For that many strings you will need a combiner box and breakers or fuses on each string. Midnite and Outback make one that will handle 2 arrays with up to 6 strings each.