Sun Yeti wrote:-Losses due to inverter efficiency (even with a good inverter, there will be at least a few percent)
VS the losses in the wires because 12V requires moving 10x the current. Parasitic losses in the wire rise by the square of current, so you're burning off 100x more power as heat in the wire using 12V LEDs than you are using 120V LEDs.
-Base power loss in the invertor. The Xantrex invertor that was mentioned earlier in the thread is very good in that it has a low standby power (which, correct if I am wrong, it uses all the time, even when it is powering things), but if all you are running is a few LED lights, that's still a significant ratio of non-useful watts to load watts.
As I believe has been noted in this thread, choosing a high efficiency (above 90%) inverter with a small base load (meaning sized properly to the load it'll be powering) is important.
Losses due to the switching power supply in the lightbulb. There are some decent LED driverse out there (efficiency greater than 80%, power factor greater than 90%), but they cost more than your average LED lightbulb, and they take up more room. To get an LED driver small enough to fit in a lightbulb, you have to make a number of sacrifices. A common one is power factor. The power company charges residental users by watts (not volt-amps) most places, so regular comsumers don't notice or mind, but many LED light bulbs have a power factor as low as 0.6. If you are generating your own power, this is a concern (although it won't actually cost you 40% more power in that example; see this thread on candlepowerforums for more info: http://www.candlepowerforums.com/vb/sho ... wer-Factor
" onclick="window.open(this.href);return false;). And on top of that, the lightbulb power supply is unlikely to be much more that 85% efficient.
Short answer to this: shop smartly. All the 120V LED light bulbs I have have an electrical efficiency above 90% and a power factor above 0.9. Sure, I had to pay for it. But if you want to cheap out and pay $5 for a A19 replacement, you're going to get crap and you deserve it.
-The switching power supply in the lightbulb can generate radio noise and interfere with radio communications (another corner they cut to make the power supplies small).
I'm a ham radio operator. I have zero problems from my 120V LEDs producing RFI. Again, I buy good LEDs only. I do have problems with CFLs and linear florescents producing RFI though.
-Lower lifespan/less reliablility. I've had a few '20 year' LED lightbulbs that died in one or two years. The LEDs were probably still good, but the power supply is a piece of sophisticated electronics, with a load of failure-prone components.
Again, buy quality. The Philips L-prize winning lamps have over 18-years equivalent run time in government testing labs and they're still going. If you cheap out, you deserve what you get.
-Heat problems: LEDs are happier the colder they are. Imprisioning them in a sealed glass hemisphere with their own waste heat and a bunch of other heat-generating electronics reduces their operating efficiency and lifespan. This is why LED lightbulbs look so crazy with all the fins and so on, trying desperately to dump heat.
This is a red herrring. Your 12V LEDs have exactly the same problems with heat. Die temperature is a function of current run through the emitter and the efficiency of your thermal path to the outside world. So those fins you mock are a sign of a job well done. If you're not doing that, you're either risking burning up the emitter or you're running a small fraction of the potential output of the LED.
My small business manufactures LED light fixtures that electrically consist of top quality LEDs,
It's nice to have you admit your post was spam.
The LEDs could take 3 to 4 times the current they run under normal conditions, so even if the charge controller goes nuts and trys to put 16 volts into the battery (and connected lights), they would still be fine (although noticably brighter). Yes, if the battery is really low the lights will get slightly dimmer, but I consider that a feature, not a bug (it lets you know your battery is getting low).
So your output varies with voltage input. Knowing the curve for LEDs, your output varies a LOT with input unless you're doing something to stabililze it. To a lot of us, that's not a feature, that's a show-stopper failure of the product. When I flip the switch, I want a predictable amount of light. So, now I have to use a voltage regulator with your product, which has roughly the same efficiency losses as inverting to 120V. If I want to know my batteries are dying, I'll look at my battery monitor, which is required tech anyway.
but good DC LED lighting will always beat good AC LED lighting until they can make inverters and LED drivers that are 100% efficient with a power factor of 1.0 and no standby power that are as reliable as LEDs (the LEDs themselves can last 20 years or more), and cost almost nothing.
The problem is that there's (as far as I've ever been able to find) no good consumer-ready DC LED lamps out there. I'm not interested until it's greater than 90 lm/Watt, CCTs of 2700K and 4100K available, and a CRI greater than 90 off the shelf that I can just walk in and pick up. That doesn't exist yet in a marketable form that I've ever seen an ad for. Sure, I could pick up a Nichia 219, but then what? I have to have the skills to solder and fabricate something usable out of it. Even once all those requirements are met, you still have the problem of how incredibly inefficient 12V power distribution is. Running 12V the length of the house is going to require either HUGE wires or be HUGELY inefficient.