200W solar panel setup

jdfnnl
jdfnnl Registered Users Posts: 15 ✭✭
in Off Grid Solar & Battery Systems #1
I am currently working on mounting a couple 100W panels on the roof of my truck and saw to my dismay that the supports I was planning on leaving in place above the panels reduces their output to less than 50%. I suppose it is clear that I need to remove anything at all above the panels for an appreciable current generation.

I was also planning to use an MPPT with the panels in series, but also consider it may be better putting them in parallel with a PWM controller. Could someone please point me in the right direction and enlighten my understanding between these two configurations?



Partial Shade really obliterates the current as shown here -->


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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    Shade on solar panels = bad harvest     Sorry. Panels need full sun
    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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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #3
    Even your test isn't a good example, if you placed the panels in full sun, then cover with a 2x4, you are likely to see, 85% loss of power or more.

    Nothing wrong with PWM if your panels are in the correct charging range for the battery bank. 17.5-19 volts for 12 volt bank, 35-38 volts for a 24 volt bank. You won't see a huge jump with MPPT with panels made to charge battery voltages. Your panels appear to be 33 cell panels, and might be a little lower voltage (VMP) so keep your distances short and wire size reasonable to minimize voltage drop.
    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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  • jdfnnl
    jdfnnl Registered Users Posts: 15 ✭✭
    #4
    Okay great, so it looks like an MPPT will be unnecessary if I have two panels connected in parallel outputting something in the proper charging range of a 12V system. Would an MPPT however help during the lower light times of day to step the voltage up? In other words, are solar panels ever running at less than ~14V during times of lower light? If not supposing a Renogy wanderer would suffice .. it seems a miracle if the panels exceed 5A even in direct sunlight, so maybe the 10A version would work, or 30A just to be safe?

    I have currently have two batteries to choose from, one 110Ah and one 100Ah SLA that I would also connect to the alternator with a solenoid between. Maybe one is better than the other for the system as described? The only constant draw would be a small compressor fridge turned off at night that draws ~3.5A when running but it might only run 10% of the time. Other accessories would include a couple 120mm fans, an led light strip and possibly an ebike charger connected through an inverter.

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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #5
    Most MPPT controllers will only downconvert the PV voltage. And they need (generally) 130% of the max battery voltage, to have enough headroom to downconvert.  A 12V system can EQ at 16V, so your array needs to be at least 20.8v for MPPT to begin to make sense

    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: 33,613 admin
    #6
    There is one company (at least) that does make Boost type MPPT charge controllers... Really for smaller systems:


    In general, it is better (more cost effective) to get more solar panels and connect them in series for higher voltage MPPT controllers. But may work well for smaller systems...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • jdfnnl
    jdfnnl Registered Users Posts: 15 ✭✭
    #7
    Okay, a parallel arrangement with a PWM seems like the clear course of action with only two panels.

    Would there be any preference for the 100Ah vs the 110Ah battery?

    On the topic of controllers, I take it charging an ebike battery through an inverter is preferable despite the inefficiencies .. rather than having a DPDT switch between the panels and two controllers, one for the house battery and another for 48V lithium. Furthermore, as a way of preventing this from draining the battery too low for the fridge, is there a straight forward way to set a comparatively higher separate low voltage cutout for the lithium charger?

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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #8
    even if you wired your 2, 12v panels in series, you would not be able to charge a 48V eBike battery

    Your best bet is to charge the bike with it's supplied charger, and use your panels to keep your 12v bank charged.

    Here's the problem.  Your eBike is another large load..  Say it has a 100w motor, and you only use 50w at half throttle. After 2 hours, you have consumed 100wh, and need to replace it.   Your 200w of pv panels are pretty well crippled with the shadows, and being flat on the roof, they can never harvest 200w, 100w for the noon hour is more likely, and you have stolen charge away from your 12v bank
    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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