New here and need some advice

solarpowernovice
solarpowernovice Solar Expert Posts: 134 ✭✭
I am trying to put together a small off-grid solar system, this is what i have so far...
Four 100Watt grape solar panels from costco / a 45 amp MPPT morningstar charge controller / 1000 watt Go Power sine wave inverter / and Four 6v 232 or 242 or 250 amp-hour golf car batteries from interstate battery(im not sure which to go with)?? I am planning on putting the panels in series and then paralleling them. With the batteries i plan on putting the Four 6v batteries in series making a 24 volt battery. I only plan on draining batteries by 30% or 40% MAX to make the batteries last longer... I have a few questions, will i need to use a combiner box / DC disconnect box or just fuses between each component? Do all these components go together? Will the batteries recharge back to 100% in a sunny day with 4.5 hours peak sun?
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New here and need some advice

    Welcome to the forum.

    This inverter; you've already bought it? If so, check the specs: if it is a 12 Volt inverter (most likely for 1kW) you will not be able to run a 24 Volt system and use that inverter.

    Next issue: 400 Watts of panel on an MPPT controller will produce about 25 Amps @ 12 Volts. That would be sufficient for 250 Amp hours, but at 12 Volts (two 6V batteries) not 24. It will also give you roughly 900 Watt hours to work with if that's 4.5 hours of equivalent good sun.

    Your MS 45 Amp MPPT controller is definitely overkill at this point. But it does leave you with room for expansion.

    Most GC2 type batteries are 220 Amp hours, btw. The 232-250 range will tend to be more expensive per Watt hour; you may want to reconsider that choice as well.

    Most important: do you have a target number for how many Watt hours you want to supply?
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    No I haven't bought the inverter yet, but I was going to get a 24 volt 1000 or 1500 watt. If I understand you right and I went with Four 232-250 amp hour 6v batteries in series @ 24volts I'd have to get 400 more watts of panels? Thats all I've bought so far is the 4 panels. I want to use 700 watts per hour for about 5 hours. here are the panel specs 100 Watt, 18 Vmpp, 5.56 Impp,
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New here and need some advice

    Yes. Since you want around 10% of the batteries Amp hour capacity as the peak charge current you get this:

    25 Amps @ 24 Volts = 600 Watts plus derating factor (77%) = 779 Watt array. That is pretty close to 800 Watts and no one ever complains about having more panel! :D

    BTW if you were to do this with a PWM controller you can estimate array size using the standard Vmp for the system Voltage. That's 35 on a 24 Volt system, so you'd have 25 Amps * 35 Vmp = 875 Watt array. As you can see the larger the system the better value you get with an MPPT type controller.
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    Thanks so much for the fast replies... So i would definitely need to wire it all thru a DC breaker box not use fuses right?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New here and need some advice
    Thanks so much for the fast replies... So i would definitely need to wire it all thru a DC breaker box not use fuses right?

    That would depend on which section of the system you mean.
    For example, using eight 100 Watt panels (and at that size array they would not be much of a bargain) and an MPPT controller you can make it two strings of four in series. This would not require any fuses or breakers for panel protection. But it would move the array Voltage much higher than system Voltage with a resulting loss of efficiency.

    A bit about array configuration: http://forum.solar-electric.com/showthread.php?16241-Different-Panel-Configurations-on-an-MPPT-Controller

    But for the circuit between charge controller and batteries as well as the one between batteries and inverter some form of over-current protection is necessary. Fuses are usually less expensive, but breakers give you the added advantages of a disconnect and repeat use.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: New here and need some advice
    Thanks so much for the fast replies... So i would definitely need to wire it all thru a DC breaker box not use fuses right?
    With either a breaker or fuses, make sure that they are rated for DC at the voltage you need.
    Both common fuses and common breakers cannot handle as high a voltage at DC as they can handle at AC.

    For high currents and voltages, it is usually cheaper to use fuses for DC than breakers, but as Coot said, you lose the opportunity to use it as a disconnect.
    (Warning: If you use a touch-safe fuse holder, so that you can pull the fuse while voltage is present without getting shocked, be well aware that that does NOT mean that the fuse holder can safely interrupt DC current when you pull it. Very bad things can happen if you do not shut off either the load or the source before pulling a fuse.)
    SMA SB 3000, old BP panels.
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    Okay i'm thinking about going to a 12 volt system now and cutting down my power usage... All i really need to power is a little pump to get water from a 5 foot deep cistern, into a cabin about 30-40 feet away. I also need 2 or 3 LED lights at night and a mini fridge rated at 161watts and maybe a laptop charger? how does this sound? good to me much cheaper :D
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    sorry i forgot to ask, does anyone know if i need to buy a special pump or will my AC transfer pump be enough? it probably only takes like 250 watts.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New here and need some advice

    The LED lights should be no trouble at all. The pump you want to measure. In fact a 12 VDC pump like a Shurflo might be better than trying to run a conventional 120 VAC unit.

    The refrigerator may be an ugly surprise. The start-up demands even on the small ones can be quite high, and if that is 161 running Watts it is more than many full-size units use! What is worse is that they have a variable duty cycle, meaning the Watt hours can add up quite quickly. For example 160 Watts running 1/3 of the time (not unusual for a refrigerator) adds up to 1280 Watt hours. As such any refrigerator is definitely something you want to get an actual measurement on, rather than going by the label.

    Laptops are usually not big power users, even when charging. Measure it, though; 35 Watts for two hours of charging (for example) is still significant.

    If we interpret your earlier statement as 700 Watts average over 5 hours that is a substantial 3500 Watt hours. That's about 1 kW hour more than my cabin uses in a day with a full size refrigerator and satellite Internet set-up.
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    okay so lets say i get a 12v DC pump, then i should have plenty of power for the pump,lights,laptop for 5 hours right?
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    if so then do they make 12 volt mini fridges too?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New here and need some advice
    okay so lets say i get a 12v DC pump, then i should have plenty of power for the pump,lights,laptop for 5 hours right?

    Not necessarily. Energy consumption is still there, although it will be less. With using the 12 Volt pump you eliminate the need for the inverter with its consumption and conversion losses running a pump and the start surge of a 120 VAC unit. On the other hand if you need to move a large volume of water or lift it a long way the efficiency pendulum tends to swing back in favour of the 120 VAC units. This should not be an issue for you with a shallow cistern and 30-40 linear run.
    if so then do they make 12 volt mini fridges too?

    They do, but again they are not necessarily better on power. Here's a thread full of looking at various refrigerators. Note how the small ones can use as much power as a big one.

    http://forum.solar-electric.com/showthread.php?12272-Just-how-bad-a-small-frige-is

    Sorry this all sounds like a lot of non-answers, but you have to examine many options to see which are best for you and then plan the power system around that.
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    OKAY this is my last question today. lol... can i run a laptop charger and 3 LED lights and a 12volt dc mini fridge all for 4 hours straight? and then the 12volt pump whenever needed? thanks for all your help today
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    woops you answered my questions already thanks
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    I was looking at this kit http://www.windynation.com/products/solar/solar-panel-kits/600-watt-24-volt-complete-grid-solar-kit
    and in the instructions > http://www.windynation.com/sites/default/files/Complete_Solar_Kit_Manual_Final%20R1.pdf < it says to use a 250 amp-hour 24 volt battery with Four 100 watt panels (see page 12 of 21). Now i am thoroughly confused :( what am i missing here? On the last page of the manual it shows SIX 100 watt panels wired for a 24 volt battery. Is this the way to go?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New here and need some advice

    What you are missing is that using only 400 Watts of panel with 250 Amp hours @ 24 Volts is going to result in a slow charge rate (about 12.8 Amps or barely the 5% minimum recommended by makers) which will be even lower if there are any loads on while charging (which there inevitably will be) or sun conditions aren't 'perfect' (which they invariably are not).

    Over the years I've helped design and repair dozens of systems, and insufficient charging caused by too few panels for the battery capacity is the #1 problem.

    BTW I personally don't like "kits"; they sell you what they've got, which is not necessarily what you need.
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    Hi again cariboo :) I see what you're saying. Someone told me i should return the Four 100 watt panels i bought at costco, and then buy Two 250 watt panels. Paired with a 45 amp MPPT charge controller/1500w inverter and Four 208 amp hour 6v golf car batteries. Would this be enough to power the loads i described yesterday? (small pump 30 minutes max down hill 40 feet / laptop 4-5 hours / 3 or 4 LED lights for 4-5 hours) maybe an ice maker? or this mini fridge i saw on youtube?... the guy says it has 85 starting watts 35W while running http://www.compactappliance.com/CRF320SS-EdgeStar-Midsize-Compact-Refrigerator-Freezer-Stainless-Steel/CRF320SS.html?cgid=Appliances-Refrigerators-Midsize_Refrigerators

    EDIT: I priced 4 of the RENOGY 250watt panels at $1200 after shipping. If i paired this with a 1000 watt sine inverter for $430 / $500 for a 60 amp MPPT Charge Controller, this equals $2130. So after buying batteries and all the hardware (for mounting/wiring)I should be right around my $3500 budget. would this run all my loads? Heres the panel specs: http://www.renogy-store.com/250-watt-panels-p/black-rng-250d.htm
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New here and need some advice

    What you could expect from two 250 Watt panels and an MPPT controller is enough power to recharge 320 Amp hours @ 12 Volts.

    208 Amp hours @ 24 Volts? That would be "lean" at about 7.6% peak current but just might make it.
    (If you're wondering: multiply expected maximum current by 100 and divide by Amp hour capacity to get the percent rate.)

    You could expect about 1kW hour AC from that much panel too. From the 208 Amp hours @ 24 Volts using 25% average DOD you'd get about 1kW hour AC as well, so it's a pretty good match. Usually the system will be happier if it has more panel capacity than battery capacity under the same terms.

    Now, will that power the items you mention? Almost certainly. But for how long? Since you don't have any fixed Watt hour number you have to ask yourself "what will happen if the power runs out?" If you have a back-up power source such as a generator, you're good.

    Let's assume the numbers on the ice maker are correct (this isn't a wise assumption to make, btw). If it runs 1/3 of the day @ 35 Watts that's 280 Watt hours. Is this something you can live with? Making up a batch of ice and then shutting down, keeping things cool in an insulated chest? There's a bonus to be had if you can run it once the batteries are charged as the power will be coming directly from the panels meaning you'd utilize power otherwise lost.

    But if it actually chews 85 Watts while making ice you'd run it for only 3 hours to get the same consumption. That may be plenty of ice for the rest of the day or even two days, depending on your usage.

    And that is the question no one here can answer for you: how much energy do you use in living the way you want to? If you can adapt to what is available it could work well.
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    I'm going to get a kill a watt meter today at the store and I'll measure all my appliances ill be using then i will be back with all the info. Then you can help me figure out how many panels/batteries ill need. Before i go can you explain how i use the kill a watt meter to get an accurate measurement of how many watt hours each device adds up to? I'm confused about starting power vs running power of a fridge/pump. Can I use the kill a watt meter on the appliances I'm going to be using while they're hooked up to a generator? Will this give me an accurate reading?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New here and need some advice

    The K-A-W is not going to capture the start surge. But it will show Voltage, Amps, Watts, peaks, and Watt hours (over time). From that you can get a good idea of the Watt hours per day (helps to 'sample' for more than 24 hours) and the start-up surge is typically 5X the running current for a refrigerator. (The only type of meter that will measure this start-up accurately costs a fortune.)
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    so do i really need to buy a K-A-W or can i just do the calculations without one?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New here and need some advice
    so do i really need to buy a K-A-W or can i just do the calculations without one?

    Get the meter. The info supplied by manufacturers regarding the power use of their equipment is as fine a work of science-fiction as you will ever see. :D The only calculating to be done is estimating the start-up surge (necessary for sizing the inverter) based on the running current.
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    Re: New here and need some advice

    I don't know where you live, but around here, the public library loans out the meters. I haven't found a store that carries them anymore.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New here and need some advice
    Rybren wrote: »
    I don't know where you live, but around here, the public library loans out the meters. I haven't found a store that carries them anymore.

    Both Canadian Tire and Home Depot carried similar units, but I can't find a listing for any such thing at either store now. It's like they want everyone to go "mail order". :roll:
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: New here and need some advice
    Rybren wrote: »
    I haven't found a store that carries them anymore.

    Here, HD doesn't sell them any more. They have a substitute, but it has much worse characteristics. When my KaW broke, I had to buy a new one on eBay.

    Perhaps NAWS should start selling them? By far the most recommended item on the forum.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New here and need some advice
    NorthGuy wrote: »
    Here, HD doesn't sell them any more. They have a substitute, but it has much worse characteristics. When my KaW broke, I had to buy a new one on eBay.

    Perhaps NAWS should start selling them? By far the most recommended item on the forum.

    NAWS does sell them: http://www.solar-electric.com/kiacpomome.html

    But we Canucks have that aggravating cross-border hassle to deal with (id est our government standing there with its hand out).
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    thanks to everyone.. thanks for the newegg link westbranch buying it now :)
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    Re: New here and need some advice
    Rybren wrote: »
    I haven't found a store that carries them anymore.

    Guess I should have specified Brick and Mortar stores in the local area :p
  • solarpowernovice
    solarpowernovice Solar Expert Posts: 134 ✭✭
    Re: New here and need some advice

    Ok i got the kill a watt and unplugged my mini fridge then waved the door around for about 2 minutes, then plugged it back in through the kill a watt meter. After 25 hours its saying .5 KWH ... can this be right? I had about 8 cold cans in the fridge and a frozen pack of hotdogs in the tiny freezer section. Oh and i opened the fridge 3 times during this period to get a drink out.