Solar panel output

Serg
Serg Registered Users Posts: 3
Hi all. I've installed a couple of solar panels 130watts each on a van in parallel, im using a Renogy dcc30s charger controller. To charge the service battery and the starter battery as well. My problem at the moment is the charger controller only accepts 25v input, and cuts off at 25.5v. The solar panels specifications said the Voc was 23.36, but in reality it goes all the way to 26.. Is there anything i can put between solar panels and charger that only lets 24 or 25 volts max to go through? Can I put a cheap controller with 24 output connected to the renogy one? I also read something about buck converters, do you know of any that would work on this set up? Thank you in advance     

 

Comments

  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,032 ✭✭✭✭✭
    edited September 2022 #2
    Wow! It's hard to believe an MPPT charger, especially at that price only has a max voltage input of 25 volts. If it were me I'd get another controller for solar only and still use this for alternator charging. 

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • Serg
    Serg Registered Users Posts: 3
    edited September 2022 #3
    Yes thats the only downfall of it. But it would work fine, if the solar panels did what they say. If I do that it would defect the proposed of the set up, to charge both battery's from solar if needed. Would it be possible to put something like this between the panels and the Ronegy?

    https://www.amazon.co.uk/Controller-Topcloud-Parameter-Adjustable-Regulator/dp/B08FCQMPV3
  • NANOcontrol
    NANOcontrol Registered Users Posts: 254 ✭✭✭
    I find about everything said hard to believe. Even a very minimal current draw should drop that upper voltage dramatically. A van has to have flat panels and that drops any power generated even more. Is it that cold there? I'd put several zeners in series to make up about 25W across the output. That should be more than enough near open circuit.  These have a certain tolerance and additional voltage may have to be made up with standard diodes, about 0.7V each.  
  • NANOcontrol
    NANOcontrol Registered Users Posts: 254 ✭✭✭
    When it is cold out you could just have a couple diodes in series to drop the voltage. A switch would short these out in warm weather.  Full wave bridges with center mounting hole to mount on some metal would be good for this giving two diode drop in voltage. 
  • Photowhit
    Photowhit Solar Expert Posts: 6,001 ✭✭✭✭✭
    Serg said:
    ... My problem at the moment is the charger controller only accepts 25v input, and cuts off at 25.5v. The solar panels specifications said the Voc was 23.36, but in reality it goes all the way to 26.. 
    Somethings wrong...

    What did you measure the VOC with? 
    Are these thin film modules? They sometimes exceed their rating for 6 months or so... Never seen a mono or poly/multi panel exceed their rated VOC. Is it a known manufacturer? Perhaps a model number?
    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.
  • Serg
    Serg Registered Users Posts: 3
    Photowhit said:
    Serg said:
    ... My problem at the moment is the charger controller only accepts 25v input, and cuts off at 25.5v. The solar panels specifications said the Voc was 23.36, but in reality it goes all the way to 26.. 
    Somethings wrong...

    What did you measure the VOC with? 
    Are these thin film modules? They sometimes exceed their rating for 6 months or so... Never seen a mono or poly/multi panel exceed their rated VOC. Is it a known manufacturer? Perhaps a model number?
    Yes they are, its this ones https://www.amazon.co.uk/gp/product/B08L7K1SFL/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&th=1
  • Photowhit
    Photowhit Solar Expert Posts: 6,001 ✭✭✭✭✭
    Not sure what you are replying yes too, the link goes to "Monocrystalline cells" panels.
    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.