Getting full power output from Panel

cswaite
cswaite Solar Expert Posts: 46
Ok, I just bought a new 130W panel with the following specs.


130 Watts Maximum Power
19.8 Volts Max Power Voltage
6.55 Amps Max Power Current
24.10 Volts Open Circuit Voltage
7.11 Amps Short Circuit Current


During peak sunlight I am pulling in about 3.5AMPS at best (charge controller shows). The angle of the panel is almost at a flat angle, as the roof is practically flat (its a mobile home). My questions:
  • Shouldn't I be expecting more than 3.5AMPS at best?
  • Should increasing angle of panel increase AMP output?

Don't know if this helps but I am using 12Gauge wire from panel to controller, maybe 10 feet of wire.

Thank you.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,422 admin
    Re: Getting full power output from Panel

    Panels flat on roof, hot day, and--are you not having smoke in the air from a large fire in So.Cal?

    I could understand 3.5 amps pretty easily (humid, hot, smoky).

    Also need to know the panel/array voltage (lower than Vmp voltage would indicate a hot panel; higher than Vmp voltage could indicate the charger things the battery is >80-90% charged).

    What Charge Controller (remote battery temperature sensor?), does the controller say what "state" of charge it is in, how big of batteries, and what voltage is the battery currently at?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Getting full power output from Panel

    Hot panel, bad angle, coupled with a nearly fully battery and 3.5 amps wouldn't surprise me. I would like to know what controller and what the SOC of the battery is.

    Tony
  • cswaite
    cswaite Solar Expert Posts: 46
    Re: Getting full power output from Panel
    BB. wrote: »
    Panels flat on roof, hot day, and--are you not having smoke in the air from a large fire in So.Cal?

    I could understand 3.5 amps pretty easily (humid, hot, smoky).

    Also need to know the panel/array voltage (lower than Vmp voltage would indicate a hot panel; higher than Vmp voltage could indicate the charger things the battery is >80-90% charged).

    What Charge Controller (remote battery temperature sensor?), does the controller say what "state" of charge it is in, how big of batteries, and what voltage is the battery currently at?

    -Bill

    Havent personally noticed smoke from the fires, im located about 2 hours north of Los Angeles, although there has been reported ashes in our county.

    Im not up at the mobile home at the moment where the panel is to check voltage of panel.

    Temperatures have been high 90's-100+ during the daytime, we are actually pretty dry here, low humidity.

    Im not up at the mobile home as mentioned so cant see the SOC%, but if I recall it usually is at about 80-90+%. Battery voltage is usually at 12.0-13. I do notice once the battery gets near the set Charge Off 13.7 it will start trickle charging and I wont even get the 3.5 from the panel even if it is peak sunlight, it will fluctuate fast, going up to 3.0 down to 1.5, etc etc, changing every second (just example) I have (2) 125AH 12v batteries connected in parallel.

    Charge controller can be found here, it is a 45AMP, and does have a temperature sensor.

    Let me know if I can provide any further information. I would just love to get closer to spec power out of this panel.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,422 admin
    Re: Getting full power output from Panel

    If your battery is near 12.00 volts with no load and several hours of rest (no load/no charge)--that is near 50% State of Charge.

    Battery FAQ
    Battery Charging Battery charging takes place in 3 basic stages: Bulk, Absorption, and Float.
    Bulk Charge - The first stage of 3-stage battery charging. Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no "correct" voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take.
    Absorption Charge: The 2nd stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.2 to 15.5 volts.
    Float Charge: The 3rd stage of 3-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it's main purpose is to keep an already charged battery from discharging. PWM, or "pulse width modulation" accomplishes the same thing. In PWM, the controller or charger senses tiny voltage drops in the battery and sends very short charging cycles (pulses) to the battery. This may occur several hundred times per minute. It is called "pulse width" because the width of the pulses may vary from a few microseconds to several seconds. Note that for long term float service, such as backup power systems that are seldom discharged, the float voltage should be around 13.02 to 13.20 volts.

    The charging voltage should really be >14.2 volts, and after it has reached near 100% (hour or more at >14.2 volts with declining current), dropping back to ~13.0-!3.6 volts or so.

    The charge controller appears to be some sort of On/Off/PWM charger... The fluctuating voltage/current may simply be how it is regulating (on for 1 second, off for 5 seconds, etc.). Some controllers are slow, others will do it hundreds of times a second (or faster).

    I don't know anything about this brand of controller.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Getting full power output from Panel

    If your battery is +90% charged the controller should be tapering the current down, so ~3.5 amps even in direct sun wouldn't be odd. On the other hand you say that the battery is between 12-13 vdc. doesn't mean much. A fully charged battery will be ~12.6-12.7, a almost dead one will read ~12.0. I'm not sure how much faith I would put in the controller however.

    Tony
  • cswaite
    cswaite Solar Expert Posts: 46
    Re: Getting full power output from Panel

    im thinking the controller isnt the nicest or maybe 100% accurate. If I use my multimeter and check amps directly on the wires before they go into the charge controller should the number on my meter show the same as the charge controller?

    I will experiment with increasing angle a bit and see if that pumps out more juice. Not only would it be better direct sun but would be off the roof so could vent a little better allowing it to cool.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,422 admin
    Re: Getting full power output from Panel

    For clamp meters... You need to make sure that it is DC capable (and I have seen a fair amount of "drift" in DC current clamps).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dapdan
    Dapdan Solar Expert Posts: 330 ✭✭
    Re: Getting full power output from Panel

    Those spec are that of the sun-130 that requires positive grounding. Wouldn't that fact also influence the amount of energy harvested in a negative ground set up?
    Not an expert on this but i recognise the specs on the panel.

    Cheers...
    Damani
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Getting full power output from Panel

    I think the positive grounding issue MAY result in a 10-15% reduction in harvest, not a 50%. I think the combination of hot panels, fully charged battery, and panel mis-alinement and cheap controller probably account for more of the loss.

    Tony
  • cswaite
    cswaite Solar Expert Posts: 46
    Re: Getting full power output from Panel

    Yes it is a Sun-130 model. What exactly is positive grounding?
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Getting full power output from Panel

    Most DC wiring systems are negatively ground referenced. Just like your car, and probably your trailer have the positive side of the circuit running through wires, while the negative runs through the frame or "ground" Solar based DC systems should be grounded as well, both to the frame of a vehicle or to "earth ground" for safety.

    The Sun panels in question, due to an anomaly in their design, they perform better with their positive side grounded. (Most panels don't care) This is, as I understand it is due to a static charge that builds up in the panel. The result of either negative grounding, or no grounding results in a slightly (5-10%) drop in performance. It hasn't been firmly established to me that this is a real problem.

    Tony

    PS Please don't call NAWS for information on this panel.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,422 admin
    Re: Getting full power output from Panel

    There is more in the thread from this quote (but, unfortunately, the Internet has appeared to "forgotten" all it knew about the issue--so, you will have to use my quotes of the text from the original documents).

    Note that "Sun Brand" and "SunPower Brand" are two completely separate vendors and that, for a few "Sun Brand" panel models, they have used "SunPower Brand" whole panels and/or "SunPower" raw cells in their private labeled products:
    When a module is operated at negative voltage with respect to ground, the surface polarization reverses. In this case the performance of the module is not affected; in fact, it can improve slightly because the front now repels light generated holes, guiding them to the back collecting junction. Figure 2 shows the situation at negative voltage.
    ...
    Figure 3 shows the current-voltage characteristic of a module that has undergone surface polarization after operating in the field at a positive voltage of 160 V. The blue line labeled “before voltage bias” shows that with surface polarization, the module output has declined to 140 W from its initial 200 W rating. After biasing the module at a minus 1000 V for one hour to reverse the surface polarization, the negative surface charge has been bled off and the module completely recovered, as illustrated by the red line labeled “after voltage bias.” The surface polarization effect is completely reversible, with no lingering effect.
    ...
    The polarization effect can be easily avoided by designing systems with proper grounding so that modules only see negative voltage. All of SunPower’s system integration partners have developed grounding procedures that prevent module operation at positive voltage. In Europe, SunPower worked closely with its exclusive distribution partner, SunTechnics, to characterize the polarization effect and to develop system configurations that prevent the effect. SunTechnics also developed a range of system solutions and electronic devices to optimize SunPower system performance and meet European security standards. For European tracker systems, SunPower worked with Solon to characterize and develop system configurations to prevent the polarization effect. In North America, SunPower modules are exclusively installed with SunPower positive-ground inverters which eliminate surface polarization.

    If a system is mistakenly installed with the incorrect grounding, modules will temporarily lose power, but no lingering effect remains after surface polarization is reversed. Because the surface polarization effect is completely reversible, once the grounding problem is corrected, modules will quickly recover to their initial performance without any further intervention.

    The above, in words (from a "SunPower Brand" white paper), describes the basic problem and solution. The problem is that positive ground off-grid systems are not common and there is no hardware designed to run the panels at positive ground while the rest of the system is negative ground.

    The cells/panels are probably find (for the price)--The kicker is that "Sun" (a private label of various products) panels do not list the grounding requirement/issue--The only way somebody would catch on to the issue is because of the sales blurb "made with high efficiency back-contact solar cells" -- which describes the "SunPower" type cells -- which have the positive grounding requirement.

    There are other "Sun Brand" products that are based on other vendor cells/product that are normally run as negative ground (I would guess that positive or negative grounding is fine with the "standard products".

    And, the actual negative grounding results (from the black-holed papers) is a reduction in power of:

    140watt/200watt= 0.7 => a 30% reduction in output (at 160 volts negative reference).

    IIRC correctly, the reduction happens when the panels are negative referenced to even a small amount (12-24 volts?)--but it did stabilize and did not get worse.

    And--Don't call Northern Arizona Wind & Sun for questions on this matter--they have nothing to add (as far as I know).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Getting full power output from Panel

    Try just bypassing the charge controller, and wire the panel directly to the battery. That should get the amps up to somewhere near 6A.
    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 ,

  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Getting full power output from Panel
    Ok, I just bought a new 130W panel with the following specs.

    130 Watts Maximum Power
    19.8 Volts Max Power Voltage
    6.55 Amps Max Power Current
    24.10 Volts Open Circuit Voltage
    7.11 Amps Short Circuit Current


    During peak sunlight I am pulling in about 3.5AMPS at best (charge controller shows). The angle of the panel is almost at a flat angle, as the roof is practically flat (its a mobile home). My questions:

    • Shouldn't I be expecting more than 3.5AMPS at best?
    • Should increasing angle of panel increase AMP output?

    Don't know if this helps but I am using 12Gauge wire from panel to controller, maybe 10 feet of wire.
    PV modules rarely develop full output current without correct alignment, unless they’re clean, and without “full” Sun. The flat (horizontal?) angle is probably not ideal, and tilting the module up for better alignment with local noon Sun should help.

    Horizontal modules also tend to collect dirt, bird souvenirs, and other environmental debris, all of which contribute to lower output current. So, you may need to wash the module off every now and then. The last time I cleaned my tilted array I saw output current increase by ~10%.

    “Full” Sun (1,000 kW/m^2, etc.) is rarely experienced. You generally need high Sun elevation, clean air quality, and low humidity.

    As mentioned, the controller charge state can also affect the module’s output current. If the controller is in absorb, float, or EQ mode, it will purposely limit current from the module to the battery and load(s) in order to maintain target battery voltage.

    Module temperature typically affects module voltage (high temp = reduced voltage) with very little impact on current.

    HTH,
    Jim / crewzer
  • cswaite
    cswaite Solar Expert Posts: 46
    Re: Getting full power output from Panel

    I appreciate all the replies. Thank you for bringing up the Positive ground information. So if im reading this correctly, if I want more of the rated output I will need to get a charge controller that is positive ground, or what would I need?

    Thanks again.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,422 admin
    Re: Getting full power output from Panel

    There are no "positive ground" based solar charge controllers that I am aware of (and certainly, I am not not in the field to no much...).

    Some controllers (Outback series??? for example) may include information in their manuals about how to do positive grounding. And--if everything else is isolated--a positive ground installation is possible (be careful, obviously, many 12 vdc appliances assume negative ground and the chassis could be "hot" with respect to the vehicle/building chassis/grounds).

    For a "mobile" applications--this brings up an interesting (at least to an engineer) issue. The typical "dry" RV is floating on rubber tires. To "properly" ground reference the trailer/panel would require you to "bond" the trailer to local earth... Drag a chain, drive a ground rod, etc... It does not have to be a "low resistance" ground--even a few million ohms would probably be enough (I used to static discharge my computer card packs I designed with a 10 MegOhm resistor--allowed static charge to be dissipated--but no ground loop/short circuit issues).

    Because of the issues with positive/negative grounding... I would think twice about using a SunPower/Sun panel that required Positive Ground for a RV/portable application.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    Re: Getting full power output from Panel

    Morningstar makes a positive ground one, the PS30M-PG, but nobody stocks it, and special order is around 4-8 weeks. About the only place that uses + ground are some of the older telephone and cell phone sites.
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Getting full power output from Panel

    The "negative ground penalty" for the positive ground module may not be too bad for a "low voltage" system. I finally connected with a dim recollection of this old discussion (lots of cobwebs to sift through :roll:):

    http://forum.solar-electric.com/showthread.php?t=1540&highlight=positive+ground

    HTH,
    Jim / crewzer