Re: (ET) Power Inverters - cold batteries, motor current draw

["David Roden" <etpost drmm net>]

On 11 Dec 2007 at 15:09, Christopher Zach wrote:

> 
> Mmm. Back in 2000 I built a pair of 6 LED lights on a breadboard 

A pair of 6?  

> to 
> provide low-level lighting in my shed at night. It's enough that I can 
> see to get in the door, and get things. Not enough to work by, but 
> that's what the halogens are for.

How many lumens?

> 
> They have been in use for 7 years now, 24*7*365, powered by the shed's 
> batteries. Total power used has been:
> 
> 3,600 watts

Wow, I hope you mean "total ENERGY used has been 3,600 Watt-HOURS." 
Otherwise there's something very unusual and extraordinary about those 
LEDs.

> 
> Over 7 years. Not too bad.Compare that to a night-light (4w) which would 
> have used:
> 
> 24,500 watts.

Again, I assume you mean Watt-HOURs.

The question is, how does the lumen output of those LEDs compare with the 
4W 
night light?  I think if you look at lumens/Watt, you'll find that for 
very 
low lumen outputs high quality / high efficacy LEDs are the champs, 
especially if you need colored light.  Cheap LEDs can be surprisingly 
inefficient even at low levels, however.

At higher lumen levels, fluorescents quickly surpass even good LEDs for 
efficacy.  I've never computed where the crossover happens, but I have the 
sense that it's pretty darn low, in either the single digits of Watts or 
possibly the low tens.

LEDs work well in flashlights because they don't drag down the battery as 
it 
becomes expended, as incandescents do.  Someday they will be a high 
efficacy 
light source for the home.  But frankly the current crop is rather 
oversold 
as a high-efficacy light source.  FWIW, a couple of companies are offering 
LED lights for home lighting.  Only a few of them meet California's 
minimum 
efficacy standards for primary kitchen lighting, and those just barely.  
Fluorescents ace those standards.  

I could see using some of the latest white LEDs for ET headlights.  HID 
would beat them for efficacy, but would probably be much more of a 
challenge 
to fit.  They (LEDs) would also be a tad pricey.  But very cool.  ;-)


David Roden - Akron, Ohio, USA

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 
Note: mail sent to the "etpost" address will not reach me.  To send 
me a private message, please use the address shown at the bottom
of this page : http://www.evdl.org/help/
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
     And what rough beast, its hour come round at last, 
     slouches toward Bethlehem to be born? 

                                  -- W B Yeats

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =