Planning for an upgrade

245

Comments

  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #32
    Re: Planning for an upgrade

    The fellow selling the panels just got back to me. He'll sell me four at $150 each.

    As a review, here are the specs:

    Max Power (Pmax), (Wp) 210
    Max Power Voltage (Vmp) 29.1
    Max Power Current (Imp) 7.2
    Open Circuit Voltage (Voc) 37.0
    Short Circuit Current (Lsc) 7.7
    Max System Voltage (VDC) 600

    I've also attached a pdf with the full spec sheet.

    The panels have been used for less than 2 years on a grid-tie system; he is upgrading to larger panels.

    Any advice on what I should look for? He'll be delivering them in the evening, so I guess that testing them is out.

    Thanks.
    Attachment not found.
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #33
    Re: Planning for an upgrade

    If you can't put an Ammeter on them and test the Isc in full sun all you can do is look for signs of physical damage, and hope.

    With a Vmp of 29.1 those will only work using an MPPT controller, no matter what system Voltage.
    · Share on Twitter
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #34
    Re: Planning for an upgrade
    Cariboocoot wrote: »
    If you can't put an Ammeter on them and test the Isc in full sun all you can do is look for signs of physical damage, and hope.

    With a Vmp of 29.1 those will only work using an MPPT controller, no matter what system Voltage.

    I might be able to get out to see them over the weekend with (hopefully) daylight available. I do have one of the DC Clamp Meters from Sears that BB and most others have recommended. If I do get a chance to test them, what steps should I follow?

    If all else fails, there is the remainder of the manufacturer's warranty on them that is transferrable. (or so he says)

    I do plan on getting an MPPT controller, but elsewhere in this thread I was lead to believe that a PWM would work, albeit with only half of the potential output.

    With a possible max output of 50+A, would this damage my planned 200-220AH 12V battery bank?

    Thanks yet again

    Jerry
    · Share on Twitter
  • Volvo Farmer
    Volvo Farmer Solar Expert Posts: 209 ✭✭✭✭✭
    #35
    Re: Planning for an upgrade

    You can test those panels with any old multimeter that has a 10ADC plug. Just put the test leads straight across the panel output and see if you get 7 amps or so.
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #36
    Re: Planning for an upgrade

    If you can get them in full sun what you're looking for is that Isc rating of 7.7 Amps. Both leads connected together withe the clamp-on meter zeroed and on the leads. You probably won't see exactly that, but something approaching it will prove they are capable of putting out current which is the main thing.

    Without the MPPT controller you won't damage the batteries, but you will be losing about 84 Watts from each panel. Possible more. Some (cheaper) charge controllers will not like the high difference between panel Voltage and battery Voltage.

    The >50 Amps potential with the MPPT controller is pretty high for a 220 Amp hour battery bank. It's over 20% charge rate. Depending on what controller you get you could limit the output Amps just in case. Otherwise, use half the panels for that size battery bank.
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #37
    Re: Planning for an upgrade

    If they are MC4 type connectors--Shade/point away from sun and plug together... Then measure Isc in full (or near full) sun. If you get >50% rated current--you probably are doing good. If you get <50% of rated current, then either you have poor sun or other problems.

    Look closely at the cells and over the j-box area for browning/blackening of the material (local over heating of conductors).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #38
    Re: Planning for an upgrade

    Thank you all for the advice and tips. I do feel better hearing things directly from people who know what they are talking about. I can read about these issues over and over, but I don't seem to absorb them as quickly as I once did.:blush:

    @ $0.72/W these beat out anything else I can find in my neck of the not-yet-white North by a factor of 3-4. The higher voltage will require a more expensive controller; however, unless I'm missing something, I think that I'd still end up better off with these than spending twice as much for a 135W panel. I THINK
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #39
    Re: Planning for an upgrade

    You're probably right. :D

    It wasn't that long ago I did a comparison for someone somewhere with Kyocera panels and Morningstar controllers showing the cost difference between two roughly same-size arrays, one using 'standard' panels & PWM and one use 'grid tie' (odd Vmp) panels & MPPT. About 400 Watts it was nearly a trade-off for the same power going to the batteries.

    For 800 +/- Watts? Probably even better. Hey! Let's do it again!

    Four KD 140's @ $284 each = $1,136 + 45 Amp TriStar PWM @ $150 = $1,286 for 560 Watts and 32 Amps peak current on a 12 Volt system
    Two KD 245's @ $331 each = $662 + 45 Amp TriStar MPPT @ $400 = $1062 for 490 Watts and 32 Amps peak current on a 12 Volt system

    Six KD 140's would be 840 Watts, cost $1,704 + $500 60 Amp controller (about 47 Amps from those panels) = $1,764
    Three KD 245's would be 735 Watts, cost $993 + $500 60 Amp MPPT controller (about 47 Amps this way) = $1,493

    Just as an idea that yes, sometime the cheaper panels with the more expensive charge controller works out better.
    · Share on Twitter
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #40
    Re: Planning for an upgrade

    That's what I figured - guess my brain isn't quite as bad as I thought.

    Four 210W @ $150 each=$600 + $500 60 Amp MPPT = $1,100 for 840 Watts and 54 Amps peak current on a 12 volt system

    Or the best local buy

    Four 135W @ $300 each =$1,200 + 45 Amp TriStar PWM @ $150 = $1,350 for 540 W and maybe 30 Amps peak current on a 12 Volt system

    I suppose if I really only need 2 panels for my proposed system, I could sell the other 2 panels and go with a smaller MPPT charger, but then I'd probably kick myself a few months down the road.
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #41
    Re: Planning for an upgrade
    Rybren wrote: »
    I suppose if I really only need 2 panels for my proposed system, I could sell the other 2 panels and go with a smaller MPPT charger, but then I'd probably kick myself a few months down the road.

    Yes, when your load inevitably grow and you realize you need 2X the battery bank. :D
    · Share on Twitter
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #42
    Re: Planning for an upgrade

    Because of the nature of my cabins and the relative positions of one to another, my plan is to construct a small shed directly below or beside the panels to house the batteries, CC, Inverter, etc and then run buried lines from there to each of the cabins (each about 50' away from the panels/shed).

    I can insulate the shed, but it won't be heated. Because the road into the camp isn't plowed in the winter, the system will essentially be in float mode from mid-late Nov to mid-late April. This is essentially how my current system is set up, except that everything is housed in a large, uninsulated, wooden crate. The previous owner had run it like this for the past 3 years with no issue.

    I guess that I'm somewhat concerned about housing an expensive MPPT CC in the shed where winter temps can hit -40. There's really not much choice, as there won't be heat anywhere.

    I must admit that I feel like a little kid on his way to the first day of school, squeezing Mom's hand all the way and looking to her for assurance that everything will be okay.
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #43
    Re: Planning for an upgrade

    Can you ensure that there are no loads during winter when there is nobody there (assuming snow covers the array) and the batteries are fully charged when the system is buttoned up for winter?

    Is it possible to dig into the earth a bit to use the ground heat to keep the batteries a bit warmer (at the risk of flooding during melt if you cannot drain the pit/basement naturally--may need a sump pump)?

    Can you (do you want to) add a couple vertical panels (keep clear of snow) to float the batteries?

    If the batteries are fully charged in an insulated shed--it would take very cold temperatures to freeze the batteries (which you don't want to do).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #44
    Re: Planning for an upgrade

    No worries.
    Disconnect the inverter when you leave. Make sure the batteries are charged and watered. Next Spring it will be fine.
    This is what I do and -40 is not unusual here either. I have 2" foam insulation around the batteries, but it isn't vital.

    Charged batteries don't freeze and keeping the array connected keeps them charged. Charge controllers don't care about -40 temps either. My MX60 has been through this for five years now and still works as new. Any controller that doesn't survive isn't any good for the application and should be replaced anyway. A little bit of current will be flowing through it every day too, keeping it warmer than ambient.
    · Share on Twitter
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #45
    Re: Planning for an upgrade

    BB:

    I can't dig down very deep - I'm on the Canadian Shield and there's solid granite about 12" below where the panels will be located. I could, however, build a berm around the shed if required.

    My current panels are at about a 45 degree angle and from what the previous owner tells me, they shed the snow fairly well.

    Coot:

    When I buttoned up my camp a couple of weeks ago, I checked the water and SG (temp corrected 1.27) and walked away. (No inverter to disconnect)

    It's good to know that the CC shouldn't have an issue with the temps. Now all I have to do is wait until I can find a bargin-priced sale on 60A MPPT CCs.


    ======

    I'd like to thank all of you for helping me out on this journey. I must admit that it is an intimidating process and I know that I would not have even considered doing this without your help and advice.
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #46
    Re: Planning for an upgrade

    "Bargain-priced"? In Canada? :confused: Just moved here, have you? :p
    · Share on Twitter
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #47
    Re: Planning for an upgrade

    I have a pretty good fantasy life! :D
    · Share on Twitter
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #48
    Re: Planning for an upgrade

    I've been reading through the manuals for some of the MPPT controllers and I've noticed that both the Morningstar and Outback units state that the max PV array for a 12V system is 800W while the Midnight units state that the max is 900W. My planned 4 panels would be 840W. Is the PV array size a "hard" limit, thus either eliminating those CCs from consideration - or driving me toward a 24V system?

    In a related note, although I really don't require a 24V system for now, I do know that loads grow and was wondering if I should just go to a 24V right off the bat.
    · Share on Twitter
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #49
    Re: Planning for an upgrade
    Rybren wrote: »
    I really don't require a 24V system for now, I do know that loads grow and was wondering if I should just go to a 24V right off the bat.

    In the first reply to this thread, Cariboocoot wrote:
    Cariboocoot wrote:
    I'm looking at whether or not you might be needing a 24 Volt system instead. Adding on to the existing 12 Volt system is probably not a good idea in any case; having separate systems gives you the safety factor of redundancy.

    The thread drifted off into water pumping. You are right to figure this out now. And yes, you should consider a 24 volt system.
    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #50
    Re: Planning for an upgrade

    You can "over panel" an MPPT charge controller by 0.77 or so without losing too much power in the middle of the day (panels+controller deratings, panels get dirty, a bit of wiring drop, etc):

    80 amps * 14.5 volts charging * 1/0.77 derating = 1,506 watts maximum "cost effective array" for an 80 amp controller

    If you live in an area with lots of sub freezing temperatures, snow on the ground, near vertical array, and clear winter skies--You may not want to over panel by that much as you could lose a bit more power due to cold weather and refection from snow..

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #51
    Re: Planning for an upgrade

    I do recall Coot's post and I guess that it's been working through my feable brain bit by bit.

    I'm thinking out loud here...

    For the short term: 2-3 year minimum, I really don't foresee a need to go over 12V as I really doubt that my daily draw (mainly weekend only) would exceed 1KWH, in fact, it will likely be less than 600WH. Beyond that, I'll be retired and will be (hopefully) spending more than just weekends at the camp. If the loads are to grow significantly, I suspect that it will happen then.



    This gives me a couple of years to learn the ropes and the ins and outs of properly caring for a battery bank. If I switch to a 24V system now, I won't have to replace the inverter in a couple of years nor will I have to purchase 4 new batteries then. On the other hand, if I go to 24V right away, I'd have to either switch the current 12V cabin lighting to AC or pick up some 24V to 12V converters.

    With a 24V system, I would be able to go with a smaller MPPT CC, but from what I've seen, the extra batteries would cost more than the difference in price between the controllers.

    Ahh, lots to consider and think about. Luckily, I have the entire winter to work through the issues - and hopefully find some good sales on equipment. I do plan on having the panels within the week.
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #52
    Re: Planning for an upgrade

    Morningstar's top MPPT controller has a 60 Amp maximum output: 60 * 12 = 720 Watts, so they say 800 Watts on a 12 Volt system.
    Outback's FM80 has an 80 Amp maximum output: 80 * 12 = 960 Watts, so they say 1000 Watts on a 12 Volt system.
    MidNite's Classic 150 has 96 Amp maximum output on 12 Volts: 1152 Watts, so it would take 1200 Watts.

    There isn't much of a problem putting a bit more Watts on a controller; it will simply 'clip' any extra power available and limit its output.

    Always plan for the future.
    · Share on Twitter
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #53
    Re: Planning for an upgrade
    BB. wrote: »
    You can "over panel" an MPPT charge controller by 0.77 or so without losing too much power in the middle of the day (panels+controller deratings, panels get dirty, a bit of wiring drop, etc):

    80 amps * 14.5 volts charging * 1/0.77 derating = 1,506 watts maximum "cost effective array" for an 80 amp controller

    If you live in an area with lots of sub freezing temperatures, snow on the ground, near vertical array, and clear winter skies--You may not want to over panel by that much as you could lose a bit more power due to cold weather and refection from snow..

    -Bill

    I've been looking at the 60A MPPT controllers. While I'm definately in the cold weather zone, I'm not really concerned about loosing power then, because the system will just be in float mode throughout the winter.
    · Share on Twitter
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #54
    Re: Planning for an upgrade

    In an attempt to really get a grip on my basic understanding, I ran my panel specs through the morningstar calculator. As suspected, it failed for a 4-panel configuration on a 12V system..

    Attachment not found.

    If my understanding of the previous posts is correct, if I went with this configuration anyway, the controller would simply clip off the excess power and no damage to the controller would occur. So I guess that the "Fail" is really an issue of not realizing the full potential of the system rather than a safety/damage one.

    So, from a controller perspective, aside from wasting some power, there should be no big deal.

    From a battery charging perspective, this system would be overkill for a 200-220 AH 12V battery bank. I assume that as long as the controller is working properly, it will regulate the charge cycle well enough to preclude damaging the batteries.

    As I've previiously noted, I really want to get my basic understanding up to speed to ensure I don't fall into the READY, FIRE, AIM trap.
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #55
    Re: Planning for an upgrade

    From my understanding of the overall system--I would agree that no damage to the controller should result.

    60 amp * 14.5 volt charging * 1/0.77 = 1,130 watt maximum cost effective array

    You are looking at over 25% rate of charge (if 200 AH battery ban, with 60 amp MPPT charge controller). That is a lot of current for a smaller bank--I would, at a minimum, get the remote battery temperature sensor to ensure the battery bank does not over heat/run into thermal run away.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #56
    Re: Planning for an upgrade

    Well you appear to know something about computers, I think the Midnite Classic Lite may be a batter charge controller and should handle the 4 panels for a bit cheaper price. It has standard charge settings for solar you can set by pin, and you can have all the information through a network connection. You can even do all the custom setting that way!
    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.
    · Share on Twitter
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #57
    Re: Planning for an upgrade

    Thank you both for the confirmation that I'm not quite as clueless that I thought I was.:p

    I have been reading the manuals for the various 60A MPPT controllers to get a better understanding of their features and how they work. I used the Morningstar Calculator only because I saw it when I was browsing their site.
    60 amp * 14.5 volt charging * 1/0.77 = 1,130 watt maximum cost effective array

    BB: I'm not quite sure I follow what you are getting at with this equation. If the calculator states the 840W is too large for the controller, how would 1,130W be the maximum cost effective array? I'm obviously missing something and recind my first comment in this post.
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #58
    Re: Planning for an upgrade

    More or less, the 0.77 (or 77%) is a typical figure of loss when operating a solar array "in real life".

    The STC ratings of a solar array are done with a bright light for a few seconds at near room temperature. This gives a Vmp/Imp rating with the cell temperature at ~75F.

    In real life, you have the cell temperature 20-40F (or higher) due to the sun beating down on the panels for hours per day (panels mounted flush to roof with no air circulation can get even hotter)--Hot panels reduce Vmp (by upwards of 20%) which reduces the amount of power available to the MPPT controller (Power=V*I; note that Imp does rise very slightly with increasing temperature but its affect is ~1/10th that of the Vmp, so is typically ignored).

    Add dusty panels, voltage drop in wiring, a bit of aging, and another 5% or so loss in the charge controller (~95% efficient)--You get the ~77% efficiency from solar panel, wiring losses, through charge controller losses.

    You can do better (folks with cool weather, clean panels, etc... have seen 82-85%--And in sub zero weather with reflected light from snow--upwards of 100% of STC rating)--But those are typically only seen rarely.

    In general, if you use the ~0.77 derating number, there will only be a few hours per year where your 60 amp MPPT charge controller will "clip" the output to 60 amps maximum.

    More or less--This is the "optimum" point for using the most solar panels and the most current out of your charge controller without spending more money (second controller, larger controller, or "wasting" a lot of panel output).

    MPPT charge controllers have the capability of limiting their output current to a "safe" level as part of normal operation--So even if the controller is clipping--There is no damage/hazard.

    PWM controllers do not have the ability to limit output current (other than shutting down).

    The MPPT current limit capability gives us the ability to do "interesting things" with the charge controller... One option that is used quite a bit--You have a 24 volt battery bank and a 12 volt load--Get a small 15 amp MPPT charge controller and a 12 volt battery bank. Connect the MPPT controller from the 24 volt battery bank (to solar panel input) and the charge controller's output to the 12 volt battery bank. You now have a very efficient step down DC to DC charge controller for your 12 volt DC loads.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #59
    Re: Planning for an upgrade

    Bill,

    Thanks for the detailed explanation. I do like the step-down idea for converting 24V to 12V.

    I sometimes think that I should be bringing you folks apples - just like back in my elementary school days.
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #60
    Re: Planning for an upgrade

    The biggest help... Start a thread about your system and any pictures you may have. Discuss the good and the bad, and what you are doing with the power, etc...

    Helping others makes it easier for us moderators/posters helping to supply answers, and helps the other readers of the forum understand what a real system looks like and other's experiences (as wells as adding to my education too).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #61
    Re: Planning for an upgrade

    I picked up my panels today. It was bright and sunny, so I was able to test the panels before purchasing them. Using the Sears Clamp meter, the current read anywhere from 6.95 A to 7.15 A. The vendor also gave me a money-back guarantee for the remainder (23yrs) of the 25 Year warantee.

    Going from 60W of panel to 840W. I'm happy.

    As an aside, the fellow I purchased the panels from has a 12.5KW tracking array. I had never seen one up close before; it was an impressive sight.
    · Share on Twitter

Categories