I've gotten my new computer system to the point where I can resume work that was put on hold when the old computer died in late January ... finally!! (New computer still not fully configured but it's usable in it's current state.)
Resuming work on a draft magazine article, Watts versus Lumens, that focuses on motorhome interior lighting. In the process, something occurred to me that's more appropriate in this thread than the article.
Many or most of our old motorhomes have two, completely separate, interior lighting circuits. One, with 12VDC light fixtures, is for use while on deep cycle battery or power converter. The other, with 120VAC fixtures, is for use when connected to 120/240VAC shore power or generator.
The 12VDC light fixtures tended to create a gloomy cave-like atmosphere. This is both an aspect of the light fixtures as well as an effort to extend time between needing to recharge the battery.
The 120VAC fixtures provided interior lighting similar to what you have in your home. (The stationary home versus your home on wheels.)
Upgrading to LED lighting means it's possible to eliminate the 120VAC fixtures and wiring. Depending on how you go about your upgrade, you can bring your 12VDC light levels to comparable to household lighting.
Simply replacing the old incandescent bulbs with equivalent LED bulbs may not change the light level. For example, 1156 incandescent bulbs and many 1156 LED replacements both produce 402 lumens. This similarity in light emitted holds true across multiple LED replacements, such as 192 bulbs. (Because these bulb can also be use in exterior lights, manufacturers have to maintain identical light levels. Otherwise, customers risk running afoul motor vehicle laws and regulations.)
It's possible to find LED replacement bulbs that emit more light but it'll require some searching. Motor vehicle bulb designations, such as 1156 and 192, are based on international standards, which is the basis for most national laws. So, manufacturers, distributors, and retailers avoid using the standard number designations on LEDs that have the same dimensions and installation while emitting more light. Alternatively, the package and literature may have a warning such as "Not for use in motor vehicle exterior signal lamps."
Replacing a fixture designed for old incandescent bulbs with a redesigned LED fixture will lead to greater improvements, both in terms of light emitted and electricity used.
-- Incandescent fixture with two 1156 bulbs ==> 804 lumens and 3 amps
-- Same fixture with two equivalent LED bulbs ==> 804 lumens and 0.5 amps
-- Fluorescent fixture (Thin-Lite 112) ==> 800 lumens and 1.6 amps
-- LED fixture (Thin-Lite LED112P) ==> 1920 lumens and 0.8 amps
Notice the significant reduction in energy consumed. This means your deep cycle battery will last much longer before needing to be recharged.
Specifically, you could install three Thin-Lite LED112P fixtures without using as much electricity as a single -- much dimmer -- fixture with two 1156 incandescent bulbs. However, you'd probably also find your motorhome's interior is uncomfortably bright with all three LED fixtures turned on.
This all means you could use a single 12VDC lighting circuit, running off deep cycle battery or power converter, with the same lighting level as a separate 120VAC circuit.
