Re: what are the considerations in using a 12v and a 24v LED?

[elnav]

The dollar stores are full of battery operated LED lights. Most require 3 cells meaning the nominal voltage is 4.5V Using a dropping resistor is terribly wasteful and definitely NOT energy efficient. I have noticed that a lot of cell phones have 4.5V charge adaptors. These are either the plug in wall cubes or a 12V DC plug adaptor for the car.

These dollar store lights are very atractive price wise so the challenge is how to make use of them if your off-grid dwelling is 12V.

The one thing you do not want is to be using a large number of batteries when off-grid. Its definitely pricy and the toxic waste is not conducive to our chosen lifesttyle with low environmental foot print.

If you have a tiny home where wire losses for a 12V system is not going to be excessive one or two of these 12V adaptors may be enough. They have good conversion efficiencies much better than a dropping resistor and put out a voltage usable by the battery operated lights. Typical charging capacity on a cell phone battery is around 150mA whereas a typical LEd draws around 10 – 15mA so one adapttor will drive several LED lights. Be careful not to load it to the maximum or it will overheat and fail prematurely. Check temperatures frequently when first ussing the adapttor to drive LED lights.

While its tempting to use very thin wires when wiring up LED

My recommendationis still to use regular lamp cord. the larger diameter wire is more robust and will stand up to abuse, abrasion, and provide better mechanical protection than for example telephone cords which admittedly would work.

A common battery voltage found in products is 6V. Be careful about simply plugging a 4.5V LED light into such a battery. The LED will be nice and bright becaause they are being over driven but they will fail prematurely.

The good news is the ‘trikle’ charge solar panels you can find in automotive sections are nominally rated 12V but will serve to recharge the 6V battereies quickly. Just don’t leave then out therre all day. I have several 6V batteries salvaged from alarm systems and use my small 12V solar panels for recharging them.