800 watts solar array

Adefemi
Adefemi Registered Users Posts: 6 ✭✭
in Solar Beginners Corner #1
Hi am in Port Harcourt Nigeria I recently set up 800 watts solar panels, two of them are 250 watts 24v each, one is mono-crystalline and the other is poly-crystalline and they are connected in parallel to make them 500 watts. I also have two 150 watts 12v mono-crystalline which are connected in series to make them 24v and i now connected then to the two other panels in parallel to make them 800 watts 24v in total, but the highest power i have gotten from them so far is just 405 watt. what can i do to get the optimal performance from the panels.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    First, what type of charge controller are you using? Are the 24v panels true 24 volt panels? do they have 72 cells each? Often 60 cell panels are sold as 24 volt (nominal) panels, and they can not reach the charging voltage needed for a 24 volt system. I suspect you are in a hot environment, which worsen's this problem.

    Typically panels will only put out about 75% of there panel rating, so 50% does seem low.
    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.
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  • Adefemi
    Adefemi Registered Users Posts: 6 ✭✭
    #3
    Am using EPEVER 40A charge controller and where i am falls withing the tropics i guess the hot climate might be part of the problem but the weather is not really hot now. i have also checked the 24v panels they are 60 cell panels not 72, what can i do to get them operating at the optimal level.
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  • softdown
    softdown Solar Expert Posts: 3,925 ✭✭✭✭
    #4
    Do you have the correct angle? pvwatts.nrel.gov will show the best angle for each season after you input your location. i am assuming they have data for the entire world though.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #5
    Can you post the panel info from the sticker on the back:
    Voc  __
    Vmp  __
    Isc  __
    Imp  __
    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 ,

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #6
    The problem is that 60 cell crystalline panels are designed for Vmp~30 volts... When you get them hot, they will drop down to (as low as) Vmp-hot~24 volts.

    To properly recharge a lead acid storage battery (24 volt bank) needs a Vmp-stc~36 volts and you need Vbatt-charging~29-30 volts (even higher if cold/equalize charging).

    The 60 cell (Vmp~30 volt) panels have been called "24 volt" panels, but they simply do not have high enough voltage to drive current through your wiring/charge controller/24 volt battery bank in warm to hot weather (common, I am sure, for where you live). (note, the panels still will output current above 24 volts--It is just they will output less than rated current).

    These 60 cell panels are perfectly good--But they are typically used on  Grid Tied power systems where you put ~10 of them in series for Vmp-array~300 VDC.

    The two "12 volt panels" you have are probably Vmp~17.5 to 18.x volts and those are fine for 12 volt batteries. And if you put them in series, are fine for 24 volt batteries.

    The standard solution for 60 cell panels is to put two or three in series, and get a "MPPT" type solar charge controller. Unfortunately, while MPPT controllers are perfect for the application and work very well--MPPT charge controllers are much more expensive than PWM type controllers (Maximum Power Point Tracking vs Pulse Width Modulated charge controllers).

    Now--For you... If your EPEVER 40A charge controller is an "MPPT" type charge controller with 100 Volts max input.. You can take your two 250 Watt panels in series (the two should have the same Imp rating--or within 5-10% match--Mixing Mono and Poly crystalline panels in series is not the best--but should work OK). Hook those to your MPPT controller and away you go.

    But that does leave you with your two "12 volt" panels. You cannot connect those with the 250 Watt panels. Your best bet would be to get a second PWM charge controller and connect the second to your battery bank in parallel with your EPEVER controller (paralleling charge controllers is generally not an issue if wired correctly).

    And--In general, on a hot day, you will be doing well to get ~77% to 81% (roughly) of the panels STC ratings... Most of it is Vmp drops as the solar cells get hot (power=voltage*current--Falling voltage means falling power). It is the nature of the system.

    -Bill

    Some links (if this is your charge controller):

    https://www.amazon.com/EPEVER-Controller-Display-Battery-Charging/dp/B01GMUPGZA

    https://www.youtube.com/watch?v=zTBrktPQdCM


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #7
    Well good news and bad news...

    The 4210A gets good reviews at Amazon and it is an MPPT type charge controller!

    That is also the bad news. MPPT charge controllers require even more head room. (voltage above the output voltage)

    The manual is here; http://www.epsolarpv.com/en/uploads/news/201512/1449040581526220.pdf

    If you read through it, it recommends that you use 2 - 60 cell panels in series for high enough voltage to charge correctly.


    The 36 cell 12 volt panels would NOT be recommended unless you had 3 of them. You could buy a simple/inexpensive PWM type charge controller to use them at the same time charging the same battery bank.

    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.
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  • Adefemi
    Adefemi Registered Users Posts: 6 ✭✭
    #8
    can i connect the two 250 watt 24v panels i have in series to get a higher voltage since the charge controller am using is MPPT, and also add a 150 watt 12v panel to the two 150 watt 12v i already have to be connected in series to get a higher voltage. and still connect them to the two 250 watt 24v in parallel to produce more power?
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #9
    Not through the same charge controller.
    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.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #10
    The only way you could share one controller with both sets of panels is if the Imp of the 250 Watt panel is the same as the Imp of the 150 Watt panel. But if the Imp of the two panels are more than 10% apart--Don't do it (can damage a panel, or lose too much power because of miss-match).

    Hmm... It is possible that both panels have Imp~8.3 amps and they would work nicely (250+150 in series, then put the two sets in parallel).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Adefemi
    Adefemi Registered Users Posts: 6 ✭✭
    #11
    Do you mean i would connect each of the 250 to 150 in series to make two set and connect the two set in parallel if they have the same lmp ?

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #12
    Yes... Exactly.

    250+150 Watt panels in series to make a single series "string"

    Connect two of the above strings in parallel to make your 4 panel array (efficient/safe).

    Only if the Imp are "close". I.e., One panel is 8.3 amps Imp, then the other panel would be Imp 8.3 amps +/- 0.83 amps.

    It is better that they match within 5% (more efficient)--But +/- 10% will work.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Adefemi
    Adefemi Registered Users Posts: 6 ✭✭
    #13
    thanks for the info i would check them out tomorrow 

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