24/7 DC solar setup

probinson99 Registered Users Posts: 1
edited July 2021 in Solar Beginners Corner #1
I am setting up a wireless fuel sensor and need to be able to power it. I plan on using power but I am having problems with understanding how to set it up properly.
The total system runs at 15 Watts @24VDC. and it has to be running 24/7. My problem is the wiring for the whole setup. it seems that I can wire my solar panel to my charger, and from there I can wire the charger to the battery and just hook up my load to the battery directly. 
My boss believes that some form of second controller is required to decide if the power comes from the solar panel or the battery and I honestly just can not figure out how to set this thing up. I have been looking for answers for 2 days.

I am not sure if that is correct or not. If you know how to set this up I would greatly appreciate the help.


  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    You've got it!

    Hook up the load to the battery and the solar panel(s) to the charge controller and from the charge controller to the batteries.

    Calculate the load based on the 15 watts x 24 hours or about 360 watt hours. It would be good to measure the load, may be more or less than the rating based on the amount of lift. 15 watts sounds pretty small. I have a tiny water pump that draws 40 watts.
    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.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Double check the DC input voltage to your sensor & electronics...

    The full range of DC Voltage on an off grid/flooded cell lead acid battery bank can easily range form 21.0 VDC ("dead" battery) to ~30-32 VDC (charging/float charging/very cold battery bank).

    If your electronics do not "like" that wide of voltage range... Then having a small buck/boost DC to DC converter to output closer to 24.0 VDC over time/temperature/state of charge--That may be helpful.


    Note: For 24 VDC battery bus to 24 VDC electronics, you need a buck/boost type converter. "Buck" mode drops from input to output. "Boost" mode increases voltage from input to output.

    If you, for example, had a 48 VDC bank and a 24 VDC load--Then you would only need a "buck mode" type converter.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Some charge controllers have a voltage controlled Load output.    For a small 15w load, I would use the controller's Load outputs, which will preserve your battery from going too low
    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

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