Join Date: May 2005
Location: Uppsala, Sweden
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This is about interior lighting of European motorhomes, it does not necessarily apply to US RVs. (Author = Boff)
Energy sources for lighting
Practically all recent MHs solely use the habitation 12 volts electric system for interior lighting. Alternative light sources like gas (mantle) and kerosene (wick) lamps, which can sometimes still be found in caravans and boats, have never been very common in motorhomes, and nowadays all but completely disappeared. In contrast to some caravans, it is also rather uncommon in motorhomes to install separate 230 volts mains lighting in addition to the 12 volts lighting. So while a motorhome is connected to electric hookup, the battery charger provides the power for interior lighting.
Incandescent light bulbs:
Ordinary light bulbs, adopted from automotive applications, have despite the fact that they represent the most inefficient way of converting electricity into light, been a very common source of light in MHs for many years. Being inexpensive and easily available everywhere, they are even nowadays fitted into a surprisingly large number of motorhome interior lights.
Since about the 1980s halogen lamps have become very popular in household and commercial decorative lighting. This has lead to mass production of a wide variety of halogen "bulbs" with different sockets and power ratings at low costs. By far the most of these lamps are designed for 12 volts operating voltage, and therefore need a transformer to be connected to the mains power supply.
As halogen lamps consume about 30-50 percent less energy than comparable ordinary incandescent lamps, and as MHs are equipped with a 12 volts network anyway, it did not take long for motorhome manufacturers to adopt halogen lighting as a more efficient light source. Modern MHs are usually fitted with a large number of halogen lights.
In contrast to incandescent lamps, fluorescent tubes cannot run directly from any power source, they have to be connected via an electrical ballast or other control gear. Nevertheless they are all in all about 5 times as efficient as ordinary incandescent bulbs. Fluorescent tubes have been around in campervans and motorhomes since the early 1970s. As operation on direct current requires an electronic control gear containing transistors, they are sometimes called "transistor lamps".
Apart from certain high-efficiency LEDs, which have not quite reached commercial availability, fluorescent lights are still the most efficient source of light available for motorhomes.
Compact fluorescent lights (CFLs), also known as "low-energy light bulbs", usually come with a built-in ballast for mains operation. They are designed to fit into existing light fixtures instead of incandescent lamps. Besides the more compact, sometimes curled-up shape there is no principal difference to normal fluorescent lamps. As only very few 12 volts fixtures for CFLs are available, they have never become very common in motorhomes.
While coloured LEDs have been around for quite some time, White LEDs suitable for illumination are a relatively recent development. Due to their development going at a fast pace, laboratory versions have already reached a luminous efficacy of 300lm/W, which is about 20 times more than that of an ordinary light bulb.
Commercially available white LEDs have already surpassed incandescent and halogen lamps, and the latest models now (early 2009) entering the market can compete with, but not yet surpass, fluorescent lamps regarding luminous efficacy.
Nevertheless, most of the "LED replacement lamps" that are designed to replace halogen lamps in their fixtures, are not quite as fit for the job as you would want it. Besides a compromised colour spectrum, many are not made from the latest generation LEDs, so their luminous efficacy might be not better or even worse than that of halogen lamps. And their reliability and durability is also often questionable, at least in relation to the price.