First a little (anal-retentive) background (if you don't care can skip to "The point of all of this"); on our maiden voyage with the camper it seemed to me like we were draining the Trojan T-125's far faster than I thought we should be. So I started researching solar, which lead me to the "Handy Bob" blog. In it he recommended the Bogart Engrg Tri-Metric battery monitor. After a little further investigation and emailing an EE friend, who is effectively off the grid, about it I decided to get one. My thought was to first understand what our demands on the batteries actually were before sizing a solar system.
http://www.bogarteng...ducts/TriMetric
As part of an energy consumption reduction scheme I replaced all of the incandescent bulbs in the original light fixtures with LED's from SuperbrightLEDs.com. I screwed up a bit as I got cool white LED's and we both disliked their bluish cast. As we really only use the outside light and the light over the cooking area I replaced just those with warm white LED's. Too repetitively expensive to replace all of them again. (As an aside, using a temperature scale to 'rate' the color of light seems really odd to me, but if you want warm white light from an LED you want them around the 3700K zone. Color up towards 5000K or more will have the bluish tinge.)
http://www.superbrightleds.com/
A friend with a bed-shell on his Tundra found 8mm wide strips of LEDs about 16' long on Amazon, and PWM dimmers to go with. These come backed with 3M adhesive tape and are shipped on what appear to be old 8mm movie reels. He bought a strip and a dimmer and enlisted my help in wiring them. I was really impressed with how much light they put out, even when viewed in daylight. So I ordered two strips, two dimmers, and some little wire connectors that allow for sharp corners. One strip over the bed on it's own dimmer and another over the kitchen/dinette on a dimmer that can be reached from outside.
LED Dimmer that he used on Amazon
LED Dimmer that I used on Amazon
Fast forward to late last week, well past the Costco deal on Grape monocrystaline 100w panels that I jumped on but have yet to install. For the first time the Tri-Metric read that the batteries were fully charged. To do that I had to hit them with my older, "dumb" charger. My little "smart" charger just couldn't get them there. I had bought a bigger "Smart" charger to be permanent on-board to replace the OE converter that was boiling the batteries. After getting it installed and letting it run until the batteries were topped off I started looking at what the various actual load demands were. I did not check the fridge on 12VDC because we only ever run that way going down the road.
The point of all of this: With everything turned off there was a 0.1A draw on the system. It took me a bit to realize that this was the draw of the meter itself. I have no idea if the meter always draws that or only when turned on. I suspect that the actual draw is less, but that it's rounding up since the display only has one place to the right of the decimal point.
Turning on the LED strip to *just* barely be on the discharge jumped to 0.2A, running the dimmer all of the way up brought the discharge to .9A
Now for the surprise (to me anyway), turning on one of the OE lights (w/ warm white LEDs in it) the meter showed a 0.2A discharge with only that light on. So the converted light fixtures put out nearly as much light on a lot less current!
In thinking about it I can only conclude the the PWM circuit itself is the main culprit. Next is to temporarily by-pass the PWM and see what just the LED strip draws at full voltage.
Edited by ntsqd, 27 January 2014 - 05:06 PM.
