For having some emergency lighting, I purchased two no-name, Chinese made, 12VDC input, 23W, CFLs (compact flourescent light) bulbs off Ebay. These are the spiral looking ones similar to the 110VAC operating ones that you can use to replace a 75W incandescent bulb. Same Edison screw-base only they operate off 12VDC.
I tested them in our engineering lab, a room that is about 24’ x 15’ where I could accurately measure input voltage and current. The light was located on a work bench about 3 feet from one of the corners. The lab has no windows and two doors that could be shut making the room completely dark.
With one 23W CFL bulb in the corner, with very poor reflecting surfaces, I could easily read a catalog with small print when eight feet away. At the opposite end of the room, I could barely read the writing on my note paper but still had enough light to do most everything else onw would need to do in a no-utility-power situation.
Power consumption by input voltage was as follows:
13.0VDC/1.33A/17.3W 12.0VDC/1.31A/15.7W 11.0VDC/1.31A/15.1W 10.5VDC/1.31/13.8W 10.0VDC/1.31A/13.1W 9.0VDC/1.34A/12.1W
There was no data on the input voltage range of the bulb. I did not want to go above 13 or below 9 VDC as that is about the limit for a 12V battery.
I had not expected the current to stay constant as the input voltage was reduced, making the 12VDC CFL a constant current load. In any case, the light output fell with the power but even at the absolute low end of what an SLA battery should be discharged to, 10.5VDC, the light output was still very good.
The CFL bulb immediately turned on with a very low 9VDC input, although long and/or small guage input wires might have an affect on that. However the low current and headroom should allow some fairly long 18awg power cables.
If you want a simple and efficient solution for a lot of light operating directly off a 12V battery, a 12VDC CFL would be a good choice. I paid $12/bulb.
NOTES: 1. For the best power efficiency, use as large as gauge wire as you can reasonably (14–18awg) get and keep the cable run as short as possible. Not a big deal with only one light but will start to be if multiple lights are on. 2. The 12VDC CFL with an Edison base can be accidently put into a regular lamp that is operating off 110VAC. I didn’t try it but can guarantee it will blow out the 12VDC CFL.
PFWAG, This interests me because I have a Xantrex solar battery/panel system. I have a DC outlet on the inverter, plus two regular plugs. Did you use this bulb in a regular lamp, plug into the regular (AC) outlet, but it only drew power at the DC level? Or did you have a lighting device with a DC adapter on it?
Interests me too! Tel us more.
That was me and the word is Tell!
Edna, the Edison base bulb (a carry over from Thomas Edison’s original work) that all screw-in light bulbs have for regular lamps are designed as a system to operate on the same 110VAC that is coming out of your Xantrex inverter.
A 12VDC CFL bulb that has the same screw-in base MUST be only plugged into a 12VDC source. It will go poof (or worse) if you plug it into 110VAC. This is one of the flaws in the system - the Edison base and AC plug are the same. I’ve noted that some people put a different wall receptacle and plug for the 12V lights so that they can’t be confused. A 1/4 inch mono phono jack seems to be popular.
Your Xantrex may have a 12VDC output but it is most likely being converted from your overall battery string. You loose efficiency in the conversion process. Whether that is more or less than simply using the Xantrex to provide the 110VAC and then use a 110VAC CFL I don’t know but in either cse it will use a lot more power than operating a 12VDC CFL off the battery directly. The big disadvantage of using an inverter for such a low power application is that they are always on drawing power from the battery. Even the ones that have a sleep mode still draw a notable amount of power over the hours in a day when the light is not on but the inverter is sleeping. Of course having an on/off switch for power into the inverter takes care of that.
The beauty of using the 12VDC CFL is the simplicity of using it on a small system where you only have one battery and only need a few lights.
Thanks for doing a real-world amperage test on these.
It definitely looks viable for my small solar system.
I would probably convert a regular lamp, and cut off the 110vac plug, replacing it with the rig runner 12vdc system I have standardized on in my house/comm room.
So I have a project for the weekend.
What did you search for on e-bay ? 12volt CF light or ???
Bird Guano,
I don’t remeber my search words but they are hard to find on E-bay. The source I got them from is no longer posting. Many of the solar and off-grid suppliers carry them, although usually at higher prices.
What is your “rig runner”?
Bird Guano, here are some 12vdc cf’s at Kansas Windpower (I’ve bought things from them before and been happy with them).
Closed to maintain Forum speed.