PWM to MPPT Sadness? Should my 3 parallel panels now be Series?

Options
Bass-O-Matic
Bass-O-Matic Registered Users Posts: 45 ✭✭
edited September 2021 in Solar Beginners Corner #1
I upgraded from a PWM to a MPPT. So far in mostly full sun (some clouds) my MPPT does 6.8 amps  and 12.9 volts out of 3 x 100w panels.... sadness?

I'm wondering if the fact that I have my panels in Parallel is the issue? I read something like that.

Should I / Can I hook these 3 in Series?

The MPPT says it take max input 100v... I assume the whole point of the MPPT is that whatever you put in it will be outputted to the proper voltage?

Here is the MPPT https://smile.amazon.com/gp/product/B08GK8NSRB/ref=ppx_yo_dt_b_asin_title_o04_s01?ie=UTF8&psc=1

"EPEVER MPPT 40A Solar Charge Controller, 40 Amp Charge Regulator 12V/24V Auto Max 100V Input Negative Grounded Controller with LCD Display for Gel Sealed Flooded Lithium Battery Charging"

Specs for the panels in attached image. They are close.. two are the same brand the third is different brand. All 100w 12v.

Follow up. According to this fella I don't need to fuse the panels if I go in series.


"If the Short Circuit Current of the solar array is less than the Maximum Series Fuse Rating of the solar panel, the array does NOT need to be fused. Fusing this type of array adds no additional protection or benefit"


Any help gratefully accepted.



· Share on Twitter

Comments

  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    edited September 2021 #2
    Options
    MPPT controller needs some overhead voltage above battery voltage for their MPPT search.  You may not have enough panel voltage to effectively use the controller.

    If MPPT cannot determine an MPPT point but panel voltage is still higher then battery voltage it may just drop back to PWM mode of operation.  

    You should be better off putting panels in series unless panels are subjected to some partial shading during the day.
    · Share on Twitter
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #3
    Options
    Panels in series will give 65V open circuit, so unless you get serious cold weather,  your 100max controller would be fine.

    MPPT controllers are tricky beasts, you need a fair amount higher PV voltage so the controller can downconvert it, but the higher the PV voltage, the more work (losses) the MPPT has.   for a 12V system 40V is a nice voltage,  You will be running about 51V, which should be fine.
    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 ,

    · Share on Twitter
  • Bass-O-Matic
    Bass-O-Matic Registered Users Posts: 45 ✭✭
    edited September 2021 #4
    Options
    I think it's all working? What do you think of these numbers. See pics.

    1. It's 4:30 here in Austin
    2.5 Manually Turned off LOAD on controller.
    2. Panels are mounted Flat
    3. I went up there and wired them in Series and removed all the fuses. Much more elegant.
    4. Batteries are Trojan T-105s
    5. My 1000w/2000w Peak pure sine inverter is on along with my Magic Chef Slighly large Mini Fridge. I know. They're hogs but it charge up and ran for a week straight with my older PWM and Costco batts. I guess Just... I would wake up to 12.2v
    6. Profile is FLD... I assume that means flooded lead acid.


    · Share on Twitter
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    edited September 2021 #5
    Options
    Your battery is fairly full so controller may be cutting back.

    45v for panel seems a little low.  Assuming its pretty hot in Austin so total Voc would be about 57-62v and Vmp about 49-50v assuming 36 cells per panel.  If controller cuts back for battery gettng full charge the voltage should be between Voc and Vmp total.  Could be wiring loss or sun level.

    But you are getting twice the power you had in parallel configuration.

    With the current you are now getting you are approaching limit for about a 100 AH lead-acid battery.
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #6
    Options
    Imp is ~5.58 Amps for your panels... So in series, would expect to see around 0 to 5.58 amps max (clear day, near solar noon, clean panels)... That number (Imp) will go down if panels are dirty, sun is off angle (Cos angle to sun--Cos 45 degrees = 0.71 or 71% of direct sun).

    More or less, if middle of day, anything over ~50% of rated current is doing well (50% * 5.58a = ) 2.8 amps is probably good (you would need to measure the actual solar energy to get more accurate--Our eyes just do not see much difference between 50% and 100% sun).

    Of course, the other limiting solar panel current will be how charge the battery bank is... More or less the battery needs to hit absorb voltage (~14.75 v for FLA batteries) and held there for 1-6 hours... Then charge controller will "fall back" to float of ~13.6 volts or so...

    At this point, cannot tell if battery bank is fully charged and floating, or if it needs more charging to get to ~>90% full state of charge. But things are looking better.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter

Categories