Remote Living > Lighting
A better mini-inverter for CFLs and such
vtpeaknik:
I have built a backup power system with batteries, PV panels, and a largish (2000W) inverter. But if I only need to run, say, one light bulb, the large inverter is very inefficient, using about 25 watts just to run itself. (It uses much less than that while in standby mode, waiting for the freezer thermostat to demand power.) Thus the idea of using an auxillary, smaller, inverter for lighting and other low-power uses such as a small radio.
A while back I posted about my attempt to use a very cheap inverter (the kind that is supposed to be used for charging a laptop in a car) to power an AC CFL off of a 12V battery. Despite a claimed 70-watt rating, that inverter could not start the CFL, and lit a 4W night light only dimly.
I also found that 12V CFLs with pleasant (warm) light are hard to find and expensive relative to AC CFLs. What to do?
With darker days approaching, I searched for other, better quality, small inverters. I found that the standby power loss, and efficiency while running one or two CFLs, is not much different between inverters in the 100-400 watt range, so getting one that is somewhat larger than the minimum may have more advantages than disadvantages.
Example 100W model - was recently on sale at West Marine for about $16 - cheaper than many 12V CFLs.
I ordered a bigger, "400-watt" (rated 320W continuous) model made by Xantrex (same brand as larger inverters popular for off-the-grid applications), which has a power switch, a cooling fan, a digital readout of input voltage and output power, and also comes with two cables. And all for $25 shipped!
(The pictures there are lousy, see better one, and specs, here - and also see my photos below.)
It arrived today and seems to work well. Standby current I measured at about 280 mA (about 3 watts). Running one 15W CFL it is quiet and cool. Running more CFLs, about 50W total, after a while it warmed up a bit (just noticable to a hand touching the case), and made some clicking sounds and once in a while the fan turned on for a fraction of a second. I think the clicking sounds are from the fan "almost" turning on. (I'm surprised the fan control circuit does not seem to have hysteresis.)
David HK:
An interesting article.
But why can't you accept working with direct DC voltage CFL's rather than going through all the bother of an inverter?
Here is an extract from a set of notes I am writing about CFL's - perhaps it may be of some use to you.
"Another new discovery in the CFL line - 12 and 24 volt DC voltage CFL's
On Sunday the 31st December 2006 I made a visit to Ap Liu Street in Sham Shui Po, (Hong Kong)to update my knowledge on light bulbs. In one particular shop I was surprised to find that 12 and 24 volt DC compact fluorescent light bulbs (CFL's) were on sale. They come in two colours - warm white and cool white - and are priced at HK$80 each and made in China (HK$80 is about US$10.25). The voltage figures of 12 and 24 volts will be of interest to people who are planning to turn their home into a renewable energy palace. The shop staff explained that the Wattage was as follows:-
volts DC x 1.2 Amps = 14.4 Watts
volts DC x 0.6 Amps = 14.4 Watts"
I cannot find any CFL manufacturer who is planning to produce 48 volt DC CFL's at the moment (Sept 2008).
David HK
Tritium:
I would love to find some in the USA at that price but the only ones I have found are 2 to 2.5 times more than that.
Thurmond
vtpeaknik:
I have looked long and hard for 12VDC CFLs in the USA and found only a few. Some off-the-grid oriented web-shops (mostly in Canada) sell them - but usually at $18 and up, plus shipping. I bought some cheaper ones mail-order somewhere and the "warm" light turned out to be much too "cool" for my household. Some 12VDC CFLs are really good, but hard to find. A local solar shop got me a 30W bulb that has very nice light - but hasn't managed to restock lower-wattage bulbs in quite a while. AC CFLs with nice light are $2 or so each. I've also read that typical 12VDC CFLs don't last very long, not as long as the AC ones.
So, although I do have several 12VDC CFLs and also some 12V LED lamps, I still want to be able to use some of my existing 115VAC lamps (and other small devices) off the 12VDC backup power system. Not just in case of a power emergency, but everyday, so as to make some use of the output of my PV panels, which otherwise only top off the already full baterries on most days. But using up the short life of expensive DC CFLs does not seem to be a net gain. That is why it is good to have one or two small inverters that really work.
scottsAI:
Vtpeaknik,
Couple post of mine back in December along the same lines.
http://www.fieldlines.com/story/2007/12/22/32623/837
I too bought the 40w yet only 4w inverters.
Found some real ones at 75w (ish) they got hot with 40w load after a while and shutdown.
100w pocket inverter works great for hours, as does the 300, 350w.
All drawing 120, (100w) 180ma (300w).
Large inverter in stand by draws 4-8 watts? if yours has On off switch turn it on with the freezer switch, saving even more power!
Have fun,
Scott.
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