High voltage, low current

BitterjackBitterjack Registered Users Posts: 3
I have a 4 panel of 140W each. I have them hooked up to 4 Enphase inverters. One of my panels produces more power than the rest. The other 3 produce about the same amount of power, but about half of the "good" panel.
The 3 underperformers have about 36 Vdc and maybe upto 1 Adc.
The good one has about 16 Vdc and over 4 Adc.
My old BEE tells me that I must have a high resistance somewhere but I can't find anything electrically wrong. I've checked, even redid, the electrical connections.
Any ideas?
Thanks in advance.

Comments

  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: High voltage, low current

    Welcome.
    How are you determining those values as none are anywhere close to what you should get from a 140 w panel.
     
    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
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: High voltage, low current

    Rotate two of the Enphase between the "good" and "bad" panels and see if the production follows the panels or the inverters.

    Also--Check the Voc and Isc of each panel. You can estimate Imp by connecting each panel (watch polarity--connecting solar panels backwards to a battery bank usually makes an "instant coffee table" out of the panel) to a car battery in full sun. The Imp-batt should be within ~10% of each other when in equal sun "charging" the car battery (you may want to put a bit of load on the battery--headlights, etc.--To keep the voltage similar when testing all the panels). Voc/Isc testing will catch ~80% of the failed panels, the Imp-batt test should catch the other 15-20% problems.

    I assume that these panels all are the same brand/model number... There are a few panels with junction boxes that allow a person to connect them in "12 volt" parallel or "24 volt" series strings (check J box wiring--But the above Voc/Isc tests should catch any major wiring problems).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: High voltage, low current

    Welcome to the forum

    The first question that's going to be asked so I might as well be the first to ask it is: exactly what are these panels?
    Enphase has a list of panels that will work with their inverters. None of them are 140 Watt, because the inverters are in the neighborhood of 200 Watts. This usually means the panels will be 30 to 35 Vmp whereas a 140 Watt panel will usually be around 17 Vmp. If you've found some that are 36 Vmp they are real odd balls.

    In service, a panel's output is dependent on the amount of insolation it receives and the load placed on its output. When those two factors are "ideal" you get Vmp * Imp = full output power. If you are seeing 36 Vmp * 1 Imp that's a pretty miserable 36 Watts. 16 Vmp * 4 Imp is a likewise unimpressive 64 Watts. How you are measuring your Voltage and current with the panels connected to the inverters could be another issue; it is not easy to do.

    Something about this makes me think "homemade panels" and "illegal grid-tie install". How close am I?
  • BitterjackBitterjack Registered Users Posts: 3
    Re: High voltage, low current

    Well, it's not illegal or homemade. However....
    I failed to notice (pretty sure it was never written except in the fine print in the manual) that the M210's need 24V to work. So....I have 4 sets of 1 120W panel wired in series with a 20W panel. Now mind you, the voltage and current ratings of the 120W panels are very similar.
    I have 3 different brands:
    1) 2 120W Infomon
    2) 2 120W Solar Cynergy
    3) 4 20W Power Solar
    I understand the insolation part. All of the panels are set at the same angle and in the same spot.
    This is a straight grid tie system with no batteries
    *Note* - I know this is a hacked solar array. I'm not expecting to get 1.21 gigaWatts (!). I just want to make back what my kids used on the computer and such. I am confused as to why they aren't the same - 1 panel shows it make about a 1kWh a day. Why don't the other 3? Why does that one make so much more?
    Thanks for all your help so far. I will try moving the inverters tomorrow.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: High voltage, low current

    You are probably not getting Vmp above the Enphase's turn-on point with the under-producers. That will severely limit their output.

    The M210's are meant to work not only with "24 Volt" panels but also with 210+ Watts. If you put the two Infomon in series on one inverter and the two Solar Cynergy in series on another you might get the right specs to activate the inverters properly and get some useful output. Should be on the nature of 210 Watts * 4 hours or 840 Watt hours each minimum (more with longer sun).

    The 20 Watt panels are quite probably useless in this application.

    I do not see how such a system could have passed any permit and inspection process, although the people who do that often don't know enough about solar to be qualified to make the decisions.
  • PhotowhitPhotowhit Solar Expert Posts: 5,653 ✭✭✭✭✭
    Re: High voltage, low current

    If I read your post correctly, your putting the 120watt panels in series with the 20 watt panels? You understand that this limits the amperage output to that of the lower panel? You might as well put 2 - 20 watt panels in series, the volatage adds but the amperage/current is limited to that of the lowest producing panels.

    If you actually have a set producing 1 KW a day, you must have 2 of the 120 watt panels connected! And yes the 3 strings left 1-120w+1-20w, 1-120W+1-20W, and 1-20W + 1-20W will all act alike! current being limited by the 20 watt panel.
    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.
  • PhotowhitPhotowhit Solar Expert Posts: 5,653 ✭✭✭✭✭
    Re: High voltage, low current

    PS- quit calling 2 or more panels in series a panel, it becomes a string.

    ...by "Well, it's not illegal..." you mean your power company has inspected and signed off on you backfeeding the grid?

    I may be the only person here, who doesn't care if you do this with out their permission, if you do it safely, you not being able to understand what is going on makes that likelyhood about nil.
    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.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: High voltage, low current

    "Well, it's not illegal or homemade."

    well, i'm afraid it is illegal without the inspection or permission from the utility. if they catch you they can throw you off of getting electric from them altogether and then you won't have to worry about how much power your kids are using.

    that's not the worst part because when one does something like this and they don't know what they are doing things can go radically wrong. best thing would be to take that down before something bad happens and disconnect it all and just be firmer with your kids by limiting their fun time on the internet. i think that makes sense, but it is your choice.:-)
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: High voltage, low current
    Bitterjack wrote: »
    So....I have 4 sets of 1 120W panel wired in series with a 20W panel.

    OUCH!!!! This is scary!
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: High voltage, low current

    And if you like to see math ...
    20 Watt panel @ 17.5 Vmp is 1.1 Amps
    120 Watt panel @ 17.5 is 6.8 Amps
    Put one of each in series and you get 35 Volts @ 1.1 Amps or 38.5 Watts

    Variations from this would be due to the exact Vmp and Imp of the panels in each string, but you get the idea: simply putting a 20 Watt and a 120 Watt panel in series does not get you 140 Watts.
  • BitterjackBitterjack Registered Users Posts: 3
    Re: High voltage, low current

    Everyone -
    yes, Penelec signed off on it and it was inspected. The electrical inspector signed off on it. They're may concern is I don't backfeed the grid during an outage (Enphase M210 is UL listed) and I don't burn down the neighborhood. It is electrically sound
    The only thing I wasn't aware of was the powersource going to the lowest current. Time to find better panels I suppose.
    Strings....gotcha.
    Oh...and the kids are handled. Power for 3 kids, my wife, and myself add up quick though.
    Thanks for the help. I'll end up disconnecting the little panels - a wasted $320 - and coming up with something better. Maybe even the right panels.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: High voltage, low current

    Even just connecting up two of the inverters with the four large panels as I mentioned before will net you more power than you're getting now.
    But this is why Enphase has a specific list of "approved" panels.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: High voltage, low current

    under some circumstances the pvs can be seriesed, but that is when their current outputs match within 5-10%. (that's why others are recommending you do a series arrangement with the 140w pvs as the currents will be withing tolerance.) the closer the match the better as less power gets lost. during this seriesing (is that a word?:confused:) of the pvs the voltages will add.

    to work properly and use all of your inverters you will need more pvs. observe the requirements set forth by the inverter for voltage and wattage. going over the approved pvs for the inverter could help you, but you were on a path that would've worked if the pvs were all of the similar 140w design in a series string of 2 for each inverter. this could exceed the ratings of the inverters, but the inverters should be held to roughly that max output point through self regulation of the output power. this gives more consistent output from the inverter at the possible loss of power at times by overfeeding the inverter. going with a pv in the area of 220w+ area will show good results and exceeding the inverter rating some will be fine as pvs aren't rated real world. i don't want to confuse you further here with these intricacies of the ins and outs of it all.

    btw, technically any change in the system warrants a reinspection, but if they only worry of the possibility of islanding then maybe they will just signoff on it understanding that you mismatched the pvs causing little output to be realized.

    sorry i sounded harsh about the kids, but i said it because conserving a watt is far easier and cheaper than generating a watt.
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: High voltage, low current
    : simply putting a 20 Watt and a 120 Watt panel in series does not get you 140 Watts.

    True, but it could get him a fire if parts of the 20 watter shorted out or developed a high resistance internal connection, as it was not designed to carry the extra current the bigger PV is capable of delivering. :cry:
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