Will this system work? What else do I need?

New to the forums (this is my first post)

I've been reading for months and its time to jump in. I ordered a cheapy inverter yesterday so now its time to ask some questions (go head and laugh).
The goal is a standalone, no frills - off-grid/RV kinda system (I was thinking I'd build it on my van) that will give me 1kwh, 2kw after I get more panels constant day power, and about 350wt-hrs night-time power. Cost is a factor, practicality a must - but I don't do "tools" that break in a year or don't work at all so... help me out.
This is what I am thinking. IN order of power flow as I understand it as well...

Panels:
(2) Sharp/Grape/Kyo 240ish watt solar panels - expanded to (4) when I get fiat in hand:p
1 - MNPV6 Midnight combiner box
Xantrex C60 Charge controller (60Amp)
(2) Trojan L16RE-B OR (2) Surrette S-530's - expandable to (4) ea when more fiat is available
Cheapy Inverter - Cobra CPI 2575 inverter
Maybe a little better one... Magnum RD 2824?

Don't blister me too bad... will this system work?
What other components might I need or.. what do I need to spend more on?
TIA
~Merlin

Comments

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Will this system work? What else do I need?

    if you have been reading for months then you should realize that 24v pvs shouldn't be used on a 12v battery bank through a pwm controller. if you insist upon using these pvs then go with an mppt controller, but you will be limited on the pv wattage for a 12v battery bank through the output of an mppt controller. this does depend on which mppt cc you look at to know what that limitation is. for example an fm80 outback mppt cc is limited to 80a out and at 12v this equates to 960w. now that was only an example mppt controller as there are others and the midnite classic 150 is capable of more amps on the output and therefor more pv power inputted.

    to go with a c60 (720w in pv) as you planned would mean running pvs that are lower in their vmp and would be generally 17-19v, but your plans of using that high of a wattage says you would be better off with the mppt and you could run the pvs of your choice within power limitations and run with greater efficiency than using the cheaper pwm c60.

    if it were me i'd go with the trojans as surrette users are reporting problems as i'm sure you've read.

    as to the modsine inverter, you can't expect to reasonably utilize more than a kw or so on a 12v battery system as the current gets very high in the wiring and necessitates extra thick wires from the batteries to the inverter. also note if you had been reading for months that it will not run any fans, compressors, electric motors, etc very well as it could 1> use more power for the same result, 2> shorten the lifespan of the appliance,, or 3> outright blow out the appliance being operated.

    the op's post reeks of a possible excuse to link to a competitor to our host, but i've doctored it and will give you the benefit of the doubt. further violations won't be tolerated.
    also note that links like amazon or ebay are usually short lived and we frown upon linking to them as you won't be able to see the link in the future.
  • System2System2 Posts: 6,290 admin
    Re: Will this system work? What else do I need?

    Got it, so basically you're saying that if I go over 2 panels (540) watts, I won't be able to use all the available wattage because of the limited output of most controller using a 12v factor system. To get past that I need MPPT or at the least a higher amperage output controller, one that can use 4 panels worth of juice, and a 24v inverter for say.. power tools (yes I do want that ability)

    As for the links, my intention was to simply provide the specs to those items because their are SO many possibilities for the equipment and rating simply cannot be assumed... not to sell those items or the company whose site they are linked to. Of course you KNOW that unless I linked them on YOUR site, that conflict is inevitable, because Wiki doesn't have model-specific links to solar devices with spec sheets. Thank you for editing out the links though. I will reedit them with your links.

    You know I almost put a disclaimer in there because I thought.. just maybe this could be a forum that wasn't about advertising or politics or some other arbitrary or polarized label, that we could simply read the facts... Can't we just talk solar?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Will this system work? What else do I need?

    Let's see if I can add some clarity (and hopefully not confusion).
    Merlin wrote: »
    Got it, so basically you're saying that if I go over 2 panels (540) watts, I won't be able to use all the available wattage because of the limited output of most controller using a 12v factor system. To get past that I need MPPT or at the least a higher amperage output controller, one that can use 4 panels worth of juice, and a 24v inverter for say.. power tools (yes I do want that ability)

    What Niel is saying is that the high Watt panels have an output Voltage that is too high to be used with a 12 Volt system and a PWM type charge controller. For 12 Volts & PWM you need panels whose Vmp is around 17 to 18 Volts. The Kyocera 240's Vmp is 29.8; that means about 40% of the panel's power will be lost if you try to use it this way. That's money down the tubes. This panel is also not suitable for 24 Volt systems for exactly the opposite reason: the Vmp is too low. These are meant to be used on grid-tie systems, and the only way to use the on off-grid without losing power is through an MPPT controller (so that the array Vmp is at least the minimum required for the system charging and any additional Voltage is converted to current).

    The 60 Amp PWM charge controller limits you to roughly 720Watts of panel, but they have to be the right Voltage panels. Any available current over 60 is 'clipped', regardless of controller type or array configuration.
    As for the links, my intention was to simply provide the specs to those items because their are SO many possibilities for the equipment and rating simply cannot be assumed... not to sell those items or the company whose site they are linked to. Of course you KNOW that unless I linked them on YOUR site, that conflict is inevitable, because Wiki doesn't have model-specific links to solar devices with spec sheets. Thank you for editing out the links though. I will reedit them with your links.

    You know I almost put a disclaimer in there because I thought.. just maybe this could be a forum that wasn't about advertising or politics or some other arbitrary or polarized label, that we could simply read the facts... Can't we just talk solar?

    This isn't politics, it's courtesy. NAWS pays for this space and they shouldn't have to pay for what amounts to advertising to competitors. In the past there have been problems with such links confusing people into thinking this was a support forum for other retailers, and NAWS would get complaints about problems with those sellers that had nothing to do with our host.

    For the most part, you only need to provide the make and model of any given component. The people here know pretty much every piece of equipment you're likely to run in to. Links to manufacturer's sites are not a problem.

    This site is not about advertising or pushing product. NAWS has never requested we operate it in that manner, only that we keep the ads for other competing retailers out and try to avoid junk links and such. None of us moderators are connected with NAWS; we're just volunteers here to keep things flowing smoothly. And yes we do link to NAWS when mentioning products; it's a courtesy to them and a good starting place for looking at equipment and prices. No one says you have to buy there.

    I'm curious as to why you picked the Cobra inverter. After your statement of not wanting to buy tools that break and picking good panels/controller/batteries - why the compromise on the inverter?
  • System2System2 Posts: 6,290 admin
    Re: Will this system work? What else do I need?

    What Niel is saying is that the high Watt panels have an output Voltage that is too high to be used with a 12 Volt system and a PWM type charge controller. For 12 Volts & PWM you need panels whose Vmp is around 17 to 18 Volts. The Kyocera 240's Vmp is 29.8; that means about 40% of the panel's power will be lost if you try to use it this way. That's money down the tubes. This panel is also not suitable for 24 Volt systems for exactly the opposite reason: the Vmp is too low.

    Ok I see SO.. I need to get panels that are about the right Vmp to charge whatever increment I have the battery bank at? 17ish Vmp for 12V bank, 29ish for 24V bank?
    I never noticed panels classfied that way.. I guess you really have to look at the specs of your panels... or lose power.
    I'm curious as to why you picked the Cobra inverter. After your statement of not wanting to buy tools that break and picking good panels/controller/batteries - why the compromise on the inverter?

    I compromised there because originally I was trying to keep it under 1500$ lol... I see that isn't really possible for what I want it to do so.. its.. want less... or spend more - can't have both ehh!
    I aimed at the Cobra because it was $1000 price difference in just about everything I can find on a specifically solar oriented retailer. I guess it's like buying tools at an Autozone -madeinchina- or buying them from Snap-on, Craftman, etc etc.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Will this system work? What else do I need?
    Merlin wrote: »
    Ok I see SO.. I need to get panels that are about the right Vmp to charge whatever increment I have the battery bank at? 17ish Vmp for 12V bank, 29ish for 24V bank?
    I never noticed panels classfied that way.. I guess you really have to look at the specs of your panels... or lose power.

    Panels are confusing things because they have three Voltage ratings: the nominal, the Voc, and the Vmp. It gets worse if some company refers to their panel as "24 Volt" (nominal) when it's Vmp is barely enough to meet the charging minimum for such a system. Usually you have a "12 Volt" panel with a Vmp around 17.5 and a "24 Volt" panel with a Vmp around 35. But there are lots of panels made for grid-tie systems that have Vmp ratings which fall outside of these convenient parameters. GT systems only need to put together strings that add up to the high Voltage required to operate them, and there's a pretty wide latitude there. Such panels can be used for off grid systems but only efficiently with the MPPT type controllers.
    I compromised there because originally I was trying to keep it under 1500$ lol... I see that isn't really possible for what I want it to do so.. its.. want less... or spend more - can't have both ehh!
    I aimed at the Cobra because it was $1000 price difference in just about everything I can find on a specifically solar oriented retailer. I guess it's like buying tools at an Autozone -madeinchina- or buying them from Snap-on, Craftman, etc etc.

    You can buy good stuff and pay the big money once, or you can buy poor stuff and pay the small money twice. :p Made in China is not necessarily a bad thing. Made in China as cheaply as possible with no quality control oversight is. Grape Solar panels are made in China. So are Xantrex inverters. Nothing wrong with either one. Some other products made 'here' have proven to be pretty poor stuff.

    Expensive hobby, isn't it? ;)
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Will this system work? What else do I need?

    it is confusing to say the least and i hope you are getting a grasp on it.
    btw, the midnite classic is very feature packed, competitively priced, and made in the usa so it would warrant your close consideration for a mppt controller choice. also, be sure the charge rate to the batteries is roughly 10% as trojan recommends. this means you can't just keep adding battery capacity as the charge rate would suffer and the batteries may not receive a proper charge. you also shouldn't wait too long to add capacity as new and old batteries aren't good to mix and this is a general statement that follows the ifs, ands, and buts talked of below.:confused:

    there are lots of ifs, ands, and buts to this and it all gets factored in to make it work right. if it were simple then we wouldn't be here trying to explain all of those ifs, ands, and buts. i could even throw in a few ors and maybes.:roll:

    i will say that if you plan to expand (doing it soon after base system is implemented) then plan for a higher voltage on the battery bank from the start. also plan for an mppt controller as there is far less losses with this type of controller and is well suited for systems 300w-400w+ and allows for a large expansion.

    for example you start with 2 230w (stc and is another one of those buts) pvs as this is 460w total. no problem here with a 12v system as 460w/12v=38.3a and well within the abilities of many mppt controllers. now expanding that to 920w (doubling the pvs) at 12v this is 920w/12v=76.7a. now you are limited to a few mppt controllers that can do that at 12v with the classic as one of them. arranging that battery bank for 24v at this point allows you to parallel 2 strings of 2 pvs in series (because of the vmp being too low for 1 pv for 24v battery bank). something happens here you need to note as the controllers are still capable of the same current output as they were rated for at 12v, but because the voltage out doubled then the power out capability is also doubled. those same 4 pvs would now be 920w/24v=38.3a and is now a very familiar number again with room to spare. if you elect to go to a 48v battery bank (controller max specs need observed) for that same 920w the result is an output of 920w/48v=19.17a. there's now allot of room to expand on the amps without exceeding the ability of the controller and i'm comparing to the 60a and up mppt controllers most commonly out there. for example with 60a controller at different battery voltages,
    12v x 60a = 720w, 24v x 60a = 1440w, 48v x 60a = 2880w.
    this max output helps determine your max input as i believe the nec would keep both figures the same even though there are losses in any pv that bring this down closer to about 77% of that give or take.

    you normally don't want to go 12v now and later go to another battery voltage as this voids the use of the inverter you would presently have. now you could plan to get rid of the cobra inverter for a better sine wave inverter with a higher battery voltage later, but should happen in less than a year without abusing the present batteries that you would also expand on along with the extra pvs to properly charge them with. see what i mean about if, and, and but?:confused:
  • TnAndyTnAndy Solar Expert Posts: 249 ✭✭✭✭✭
    Re: Will this system work? What else do I need?

    Also, for what it's worth, if you go with a better (MPPT) charge controller, like the Outback FX60 or FX80, you can drop down to a Midnite 3 circuit box, as you can wire your panels in series ( sets of 2, or 3 ) and up the voltage to (35 x 2) or (35 x 3) as the controller has a 150v input limit, and let's you select whatever output you want (12,24,36,48v). You'd save a little on the box, the breakers, extension leads, and can use smaller wire with higher voltage. It adds up !

    The panel array limits on the FX60 are:
    (as per Outback)

    12v out.....800w
    24v out.....1600w
    48v out......3200w

    For the FX80:

    12v out......1200w
    24v out......2400w
    48v out......4800w
  • System2System2 Posts: 6,290 admin
    Re: Will this system work? What else do I need?

    Hmm hmm... I think I need to set out to spend more hah.

    Ok I get the 12-24-48v Vmp thing..

    What is "nec". I get most of the terminology here, that one I don't recognize.
    niel wrote: »
    12v x 60a = 720w, 24v x 60a = 1440w, 48v x 60a = 2880w.
    this max output helps determine your max input as i believe the nec would keep both figures the same even though there are losses in any pv

    Ok so my original system would work, 2 panels (550w), C60, 2 [email protected] and 12v inverter, I just wouldn't get sawzall and refrigerator power out of it AND it wouldn't be expandable without changing the controller and inverter AND I'd be wasting power from "non 12v" Vmp panels?
    How's my reading comprehension so far 8)

    So if my "final" system is gonna be a 1000w array, I should be thinking a 80A-MPPT or Midnight classic kinda higher amp controller to get full use of the panels as well as charge the total (4) 400aH-ish batteries around 10%
    SO (4) x [email protected](ea) series wired to 24V = 400aH which needs about 24vX40A charging, easily managed and expandable by say the Outback FX60/80

    ONe last thing, since the controller seems to be the critical point here... any pro/con guidance on choosing the Midnight classic over the Outback FX80?

    I can see they both have full 80A @ 104*F, which I might actually use here in SC (wipes forehead as its still in the mid-70s mid-november...)
    I see they both support at least 60V output charge, the Classic up to 120V and both have about 150V input voc ratings, the FX80 a tad less according to spec sheet. Both also have a 5-year warranty.. 10yr available from Outback (impressive)

    Any pebbles to tip the scales?

    I can tell you guys like the Outback stuff, even before I knew what PV meant I'd heard about the awesomeness of Outback equip.
    In case you haven't noticed I am trying to buy American - doing my part to give you and me a job seems a good idea! (insert political rant... and now remove it)
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Will this system work? What else do I need?

    guess i better address this point by point. (in bold)
    Merlin wrote: »
    Hmm hmm... I think I need to set out to spend more hah.

    Ok I get the 12-24-48v Vmp thing..

    What is "nec". I get most of the terminology here, that one I don't recognize.

    national electrical code. electricians and do it yourselfers have to follow these rules when governing bodies make them law.

    Ok so my original system would work, 2 panels (550w), C60, 2 [email protected] and 12v inverter, I just wouldn't get sawzall and refrigerator power out of it AND it wouldn't be expandable without changing the controller and inverter AND I'd be wasting power from "non 12v" Vmp panels?
    How's my reading comprehension so far 8)

    the only way your original proposed pvs will work well is by an mppt controller as these pvs are not in the nominal range that is good for a pwm controller. the following is an example of a pv that will work with a pwm controller,
    http://www.solar-electric.com/kyso130wa12v.html
    now the evergreen line i believe had some in the acceptable range as well and you can still get them or their equivalents for now as they went bankrupt. that makes future expansions tough to do when the pv availability is in question. my advice is to skip the c60 altogether and save if you have to to get a good mppt charge controller.


    So if my "final" system is gonna be a 1000w array, I should be thinking a 80A-MPPT or Midnight classic kinda higher amp controller to get full use of the panels as well as charge the total (4) 400aH-ish batteries around 10%
    SO (4) x [email protected](ea) series wired to 24V = 400aH which needs about 24vX40A charging, easily managed and expandable by say the Outback FX60/80

    i think you grasped this part of it as 40a would be outputted by the mppt cc to charge the 400ah battery bank at 10%. there is a bit of wiggle room there as exactly 40a won't be critical.

    ONe last thing, since the controller seems to be the critical point here... any pro/con guidance on choosing the Midnight classic over the Outback FX80?

    i have my opinion and you can see in my signature line that i have a classic so i might be a bit biased here, but either would work for a 40a application. the classic can go a bit higher in amps out than the fm80 and may play a factor in an expansion. you have to read and moll over the info on both to decide. the guys that make the classic were the makers of the outback mx60 which is the blueprint for much of the fm series, but with some modifications by the present crew there. boB and robin founded and left the company to form midnite solar.

    I can see they both have full 80A @ 104*F, which I might actually use here in SC (wipes forehead as its still in the mid-70s mid-november...)
    I see they both support at least 60V output charge, the Classic up to 120V and both have about 150V input voc ratings, the FX80 a tad less according to spec sheet. Both also have a 5-year warranty.. 10yr available from Outback (impressive)

    actually the classic can go higher than 150v by about the battery voltage without damage and the fm80 can't do that. it still needs to be under 150v to work though for the 150 model. midnite i believe is also offering an extended warranty and you don't quite have the specs for the classic down quite right. there are many models as these can go with a higher input voltage, but the classic 150 should do you i think. here's a link to some specs,
    http://www.solar-electric.com/mnclassic.html
    you can also read the manuals for many of the controllers to know what each is like specifically.
    in the link i just gave you there's more info available you might want to look at by clicking details.

    Any pebbles to tip the scales?

    i don't like to throw many stones as they get hurled back in spades.:cry::p

    I can tell you guys like the Outback stuff, even before I knew what PV meant I'd heard about the awesomeness of Outback equip.
    In case you haven't noticed I am trying to buy American - doing my part to give you and me a job seems a good idea! (insert political rant... and now remove it)

    both are good, but midnite has the work being done here in the states. many of the parts for both are unavoidably made outside of the states.
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