What can I put on a C-40?

MarcelMarcel Solar Expert Posts: 39
I have 4 77 watt panels and 4 100 watt panels that I want to put on one C-40. The ISC's for the panels are 5.29 for the 77 watters and 4.96 for the 100 watters. 708 watts total. Will the C-40 take all of that? Can you help me out with wiring advice. This is a new one for me. Thanks a lot.

Comments

  • bmetbmet Solar Expert Posts: 630 ✭✭
    Re: What can I put on a C-40?

    What is the Vmp of these panels?
  • MarcelMarcel Solar Expert Posts: 39
    Re: What can I put on a C-40?

    Is that the VPMax? If so, its 17.0 for the 77 watters.

    I'm not sure about the 100 watters. They are Solarex. The data sheet says under voltage: open circuit 28.2, rated 22.5. Not sure what that means.
  • bmetbmet Solar Expert Posts: 630 ✭✭
    Re: What can I put on a C-40?
    Marcel wrote: »
    Is that the VPMax? If so, its 17.0 for the 77 watters.

    I'm not sure about the 100 watters. They are Solarex. The data sheet says under voltage: open circuit 28.2, rated 22.5. Not sure what that means.

    I don't know either, because those numbers are higher than my experience with a 12 V panel, but too low for a 24 V panel. Could there be a typo?
  • BB.BB. Super Moderators, Administrators Posts: 31,614 admin
    Re: What can I put on a C-40?

    Voc, voltage open circuit at 70F (higher in very cold weather) is the maximum rated input voltage of the charge controller.

    Vmp is voltage maximum power at 70F (usually 20% lower than Voc (and lower yet in full sun and hot panels).

    Both numbers are important when designing your solar power system.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MarcelMarcel Solar Expert Posts: 39
    Re: What can I put on a C-40?

    These panels are all 12 volt. I'm trying to figure out the VMP for the 100 watters. Is the VMP the open circuit number or the rated number?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: What can I put on a C-40?

    The short answer is "no".

    Four 77 Watt panels = 308 Watts + four 100 Watt panels = 708 Watts total. Divide by nominal system Voltage of 12 and you get 59 Amps - in excess of the C40's maximum. Never mind trying to do the "fancy math" - it still comes very close to the controller's maximum limit; almost no breathing room.

    Plus, with one set of panels having a Vmp of 17.0 and the other et having a Vmp of 22.5 (yes it's possible) you're going to lose some power potential to heat.

    So it could work, but it's not going to be very efficient and will probably be pretty hard on the controller.

    The Solarex's "odd" Voltages indicate they were meant to be used for grid-tie or with an MPPT controller.
  • MarcelMarcel Solar Expert Posts: 39
    Re: What can I put on a C-40?

    Does it help that our system is 24 volts?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: What can I put on a C-40?
    Marcel wrote: »
    Does it help that our system is 24 volts?

    That makes it worse. :roll:

    Two 17 Volt panels in series = 34 Volts
    Two 22.5 Volt panels in series = 45 Volts

    Neither hits the "sweet spot" of 35 Vmp for a 24 Volt system, but the smaller panels come close.
    The difference is so great between them that I wouldn't recommend trying it. Something like 25% of your power from the large panels is going to go to heat, not charging the batteries.

    The current rating (and really you need the Imp here) on the two are close enough you could run one of each in a series: 17 + 22.5 = 39.5. That too is a high Voltage for a "24 Volt" system, but I think you'd only be losing about 11% that way (may have done the math wrong).
  • MarcelMarcel Solar Expert Posts: 39
    Re: What can I put on a C-40?

    Well, that is a big fat bummer. I just don't want to have to buy another charge controller. gotta think.
  • snuffysnuffy Solar Expert Posts: 72 ✭✭✭✭
    Re: What can I put on a C-40?

    4 series strings at 39.5 volts each string at something less than 5 amps from each string for a total of less than 20 amps out of the series parallel arrangement. The C40 is rated for 40 amps continuous DC and a max input of 125 VDC. I don't think you'll fry the C40. But you won't get 700 watts of juice to the battery bank. Maybe 500.
  • mike95490mike95490 Solar Expert Posts: 9,261 ✭✭✭✭✭
    Re: What can I put on a C-40?

    What is your battery voltage?

    If you can post the specs off the backs of both types of panels
    Vpmax
    Ipmax
    Voc
    Isc
    we won't keep asking about what's this
    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 ,

  • MarcelMarcel Solar Expert Posts: 39
    Re: What can I put on a C-40?

    I forgot about having a ProStar-30. Can I put the 4 77watters on that? 4x77=308. 308/12 volts is 26. My system is 24 volts. Will the ProStar-30 work with a 24 volt system?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: What can I put on a C-40?
    Marcel wrote: »
    I forgot about having a ProStar-30. Can I put the 4 77watters on that? 4x77=308. 308/12 volts is 26. My system is 24 volts. Will the ProStar-30 work with a 24 volt system?

    Yes the Prostar30 is 12 or 24 Volt. Run two of the 17 Volt panels in series and you get 34 Vmp, which just might work for charging a 24 Volt system.

    The main problem is with the other panels' "odd ball" 22.5 Vmp, which doesn't work out to proper charging Voltage for a 24 Volt system no matter how you configure them (using a PWM controller such as the C40 or Prostar30). One is too low for the system, two in series is too high.

    I think you'd be better off running four strings made of one each of the two panel types into the C40.
    Vmp 39.5, current around 5 Amps +/- per string * 4 strings = 20 Amps. You'll probably only lose 10-12% of the total power this way. Without going to an MPPT controller you're not going to get that back.
  • PhotowhitPhotowhit Solar Expert Posts: 5,563 ✭✭✭✭✭
    Re: What can I put on a C-40?
    Marcel wrote: »
    Does it help that our system is 24 volts?

    I would say the answer is yes since you will be well with in the 40 amp rating of this charge controller at 24 volts, you still have the miss matched panels to deal with but you'll not go near the amperage as only the voltage adds when run in series.

    I can't recall for sure, but I believe if run series the 2 panels will not exceed the amperage of the lowest rated panel, and the voltages will add, So you have losses that way as well, might be time to look for a Rogue MPPT charge controller for the 100 watt panels.
    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.
  • MarcelMarcel Solar Expert Posts: 39
    Re: What can I put on a C-40?

    Maybe i should put those SunWize panels on the MX60. I have Kyocera 120's on that now. Their VPMax is 16.9. Would it be better to put the 120's on a C-40?
  • PhotowhitPhotowhit Solar Expert Posts: 5,563 ✭✭✭✭✭
    Re: What can I put on a C-40?
    Marcel wrote: »
    Maybe i should put those SunWize panels on the MX60. I have Kyocera 120's on that now. Their VPMax is 16.9. Would it be better to put the 120's on a C-40?

    Likely it's close to a draw, better in summer worse in winter...

    ...is this the first we've heard about 4 kyocera panels? what are their specs?
    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.
  • MarcelMarcel Solar Expert Posts: 39
    Re: What can I put on a C-40?

    The Kyocera 120's are: ISC 7.45, VOC 21.5, IPMax 7.10, VPMax 16.9.

    I think I got the numbers right on the 100's. Didn't wuite understand the terminology on the data sticker. Here it is directly: short circuit 4.96, rated 4.45, open circuit 28.2, rated 22.5. Did I mess something up?

    I thought that the 120's would work better on the C-40 and the 100's on the MX60 since it is MPPT.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: What can I put on a C-40?
    Marcel wrote: »
    The Kyocera 120's are: ISC 7.45, VOC 21.5, IPMax 7.10, VPMax 16.9.

    Oh good; more panels that are just a tad out of expected range. :roll: At 16.9 Vmp they're a bit low for 12 Volt charging, and two in series would be low for 24 Volt systems.
    I think I got the numbers right on the 100's. Didn't wuite understand the terminology on the data sticker. Here it is directly: short circuit 4.96, rated 4.45, open circuit 28.2, rated 22.5. Did I mess something up?

    I don't think you got that wrong. I'd interpret it at Isc 4.96, Imp 4.45, Voc 28.2, Vmp 22.5.
    I thought that the 120's would work better on the C-40 and the 100's on the MX60 since it is MPPT.

    In this case I think you might drive yourself mad trying to figure out which set of oddball panels will give you the least over-all power loss when matched with which controller.

    If nothing else this thread will serve as an object lesson on the problems of trying to add panels later or use mismatched panels together. :cool:
  • mike95490mike95490 Solar Expert Posts: 9,261 ✭✭✭✭✭
    Re: What can I put on a C-40?
    .....

    In this case I think you might drive yourself mad trying to figure out which set of oddball panels will give you the least over-all power loss when matched with which controller.

    If nothing else this thread will serve as an object lesson on the problems of trying to add panels later or use mismatched panels together. :cool:



    There ought to be an app for that !
    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 ,

Sign In or Register to comment.