G23 5w UVC bulbs run from my 100w solar panel

novy441novy441 Registered Users Posts: 3
I am trying to find out how to configure and wire a series of 2 pin, G23 UVC lights that will run when the panel produces enough power. 100W panel. This is off grid, with limited amount of sun, 2-4 hrs a day.  The bulbs are 5w, .7A. Can I wire them directly to the load side of the controller, or do I need a DC/DC Buck to manage theout put of the load side, or do I need some sort of ballast.  Any help or diagrams would be greatly appreciated.


  • BB.BB. Super Moderators, Administrators Posts: 33,318 admin
    Welcome to the forum Novy441,

    I am guessing these bulbs (2 pin type):


    Yes, florescent tubes (including UVC type) need a ballast... Which provides high enough voltage (something like > 120 volts) and once the arc has started, limits the current so as not to burn out the bulb.

    Don't know much about these specific lamps... But you do have several ways to go (links are just FYI--I have not used these parts/products and don't know anything about how good they are, pricing, etc.):

    First, you would need a socket:


    And a ballast... I would contact this company and see what they have available:


    Florescent bulbs are going away quickly... And It appears that Robertson has already walked away from the 12/24 VDC ballast market (dropped their products).

    You might also contact a bulb retailer and see if they can help you find a ballast:


    Solar panels have a pretty wide output voltage from zero (no sun) to 17.5 volts or so (voltage maximum power) to 22 VDC or more (cold weather, open circuit voltage)... Many times you will need some sort of DC to DC converter to stabilize the DC voltage for most loads.

    Or find an AC inverter that will run directly from solar panels (not very common).

    Adding a battery bank + charge controller + AC inverter is a solution--But one that costs more and has more maintenance (batteries go bad, flooded cell lead acid need water added, protection against over discharging, etc.)...

    I will look around a bit more--But I do not see an easy/cost efficient way of doing what you have asked...


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    edited July 2021 #3
    Eventually, there will be genuine UV-C LED's coming on the market.  Current ones only last a couple hundred hours, OK in a RV for weekends, but not ready for household use. 
    When you find "germicidal LED's" actually verify the wavelength is in the "C" band and not outside. Many fakes being marketed this year for COVID panic. UVC is around 250nm

    This is a good article about UVC for fish tanks.  Note that these bulbs run 24/7 and are always at operating temps, Domestic UVC tubes take 20-30 seconds to warm up and you get untreated water for that period.



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  • novy441novy441 Registered Users Posts: 3
    This is an RV off grid application. The ballast part is where I am getting confused. Most of the ballasts are AC to DC. So 120v to 12v. But since the panel output is DC and the LED UVC bulbs are DC, wouldn't I just need a DC/DC buck to throttle down the volts coming out of the  controller? I did find this page as well.  https://www.gadgetronicx.com/uv-disinfectant-lamp-powered-solar-power/  but the lights are no where to be found. Thanks.

  • BB.BB. Super Moderators, Administrators Posts: 33,318 admin
    Using UVC LEDs is just like any other LED (voltage and current specific to the LED(s) you are looking at).

    A "ballast" is really any circuit the limits current to a specific value. In the Link you provided, the resistor to each LED is the "ballast"--And a DC to DC buck converter is used to regulate the solar panel voltage to a specific voltage so that a simple resistor can be used as the Ballast.

    Resistors work fine, but are not efficient--The resistor turns the "excess voltage" into heat. There are DC current source circuits that are also used as ballasts to limit current flow more efficiently.

    LEDs need current regulation because their IV curve is a very "sharp knee" where if you set 5.2 volts (example), the current through the LED will vary based on the particular LED, and temperature of the LED... And the current can "run away" and overheat the led.

    And there are "tricks" you can do to limit losses and amount of electronic hardware... For example, you can take two UVC LEDs and connect them in parallel to your 17.5 volt solar panel... Each LED will run at 5.2 volts (approx) and have its own resistor dropping (17.5-5.2= ) 12.3 volts. Or you could put the two LED in series and use one LED (or active ballast) and drop (17.5-10.4= ) 7.4 volts (one "ballast" and less voltage drop across resistor, more efficient).

    UVC is dangerous, and getting UVC LEDs, designing a board to hold them, the ballast, and having materials to hold the UVC LEDs that are not degraded by the UVC, and deal with any possible ozone generation--Is not an easy job (I would guess).

    Are you looking to make your own RV Water drinking water sanitizer (or some folks have recirculating showers and could want UVC sanitizer)? Is powering directly from a solar panel an "advantage"? Most RVs are going to have 12 or 24 VDC battery systems, and even 120/240 VAC power available--So running directly from solar for a smaller system (5 watts over 2-4 hours is not a lot of off grid solar energy--20 WH or less) would not be much strain on an RV's power system...

    You might try EBay for UVC LED components and bulbs... Seems to be a fair number of vendors from China there--So don't know quality/true UVC or not...

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • novy441novy441 Registered Users Posts: 3
    The application would be to kill mold and bacteria in the RV while I am not there. Since it sits in the woods and has a lot of rain, I put in two solar DC attic fans that move the air around and do a good job. When I am there, I run a 120v UVC lamp off my generator for an hour to kill the mold, but if I can get a system that runs the UVC bulbs like these  https://www.amazon.com/gp/product/B087BZC3PH/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1, while I am not there, even a little time a day, it would go a long way for air quality and mold control.  My hope was to use these bulbs, with a G23 socket and wire parallel 5-6 bulbs to the load side or a DC buck off the load side.  

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