Automotive LED lights for off grid lighting

I know it is a bit silly, but I find great satisfaction making light fixtures. I usually refurbish and repurpose old fixture parts or sometimes just take old tomato sauce jars and other containers to make new fixtures. When I bought my 145 watt solar panel to experiment with solar energy, one of the first things I did was get some LED lights and make a few light fixtures. I leave these on in my shed 24/7 since I rarely ever tax my system and have the energy to spare. Also, I had bad luck with much older LED products, so I was really interested in the light output and longevity of newer surface mount LED lights.

I ordered some cheap LED bulbs on Amazon that were made as automotive replacements. Since 12V nominal solar power should generally fall within the range of a 12V automotive power system, as well as having more stable voltage, I figured these would be great for task and emergency lighting. I installed 2 cool white 4 watt festoon base bulbs which are typically used in car dome lights. They worked pretty well, but would get quite hot after a while. Since this was inside a shed that gets a fair amount of Florida sun, I decided to cut up some old computer heatsinks in the hopes of extending their lifespan. I first turned these on in October 2013 and they still run fine today after being on virtually the whole time. They have only been off briefly when doing a little rewiring.

Since that was a success, I decided to hunt down some warm white LED bulbs. I figured the warmer color would be good for certain tasks and to help avoid disrupting sleep cycles which can be a concern with bulbs that put off more blue light. I ordered These Warm White LED Bulbs from Amazon, and they work well. I only chose those because it said 'fulfilled by Amazon', which means it wouldn't take a month to ship in from China.

They have half the number of surface mount LEDs, so I am guessing they draw half as much energy, or about 2 watts @ 14V. They don't get nearly as warm as the 4 watt LEDs, so I didn't feel the need to add heatsinks to them. They were only 36mm as opposed to my other bulbs that are 42mm, but I was able to make them work in one of my fixtures for testing. I have one attached to my desk in the shed to illuminate my keyboard. It obviously isn't quite as bright as the other bulbs, but I like using the warm white bulb at my desk and it works great for task lighting. I'm going to string a few of them together and bring them with me the next time I camp out on my land. Once I get my shed built out there I will probably make some small fixtures and install them there.

There are lots of different options for LED lighting. I really can't see spending several dollars a bulb and using an inverter to run LED lights off grid when I can use cheap automotive LEDs. I have had great luck with the surface mount LEDs running for a long time and not having a drastic drop off in light output after running a few hours like some of the other LEDs out there. The Festoon base bulbs are good for making your own fixtures because it is easy to bend a piece of solid copper wire into a shape that holds the bulb, plus they send light mostly in one direction for task lighting. Other bulb styles would probably be better for general illumination. It can be slightly time consuming making your own fixtures and running wires, but I'm less than $20 poorer and I have 20 bulbs to take care of most of my lighting needs.

That's VERY cool. I'd love to see some pictures!

Being situated in an offgrid RV for the time being (cabin is still being planned and logs are slowly being cut), this is the direction we went as well - LED replacement bulbs for the 1141 automotive bulb in all our light fixtures. They've been working awesomely We've got several warm white and a couple cool white in areas like the kitchen where the more intense light is better appreciated. With all 9 of these lights in the RV on at the same time, we don't even see a 0.1V drop in system voltage, so it certainly isn't much draw The laptop and dsl modem, when plugged in, suck down 2 to 3 times as much power, dropping our system voltage by 0.2V, for comparison.

We're powered with 2x100W panels and 2x100ah deep cycle agm batteries - have to run a generator once or twice a week during the cloudy winter months to keep up with our overall power demands but haven't needed to since early April. Really hoping to add a 3rd 100w panel and a 3rd battery at some point, but finances are, of course, always the biggest challenge when starting from scratch on raw land like this.

Anyone not big on experimenting with building their own electrical systems, though, could simply pick up or scavenge a few of the standard RV 12v light fixtures for cheap for use with these LED bulbs. They do put out a very decent amount of light for the small amount of power draw, enough so winter lighting becomes a complete non-issue when it comes to power conservation on solar like this.

That is one of the great things about solar - people aren't as afraid of low voltage. The cost of components going down over time makes the cost of entry pretty low. I see a lot of people getting caught up with things that are less than optimal, such as the Harbor Freight kit. I know some places are putting together kits that are a better value than the one from HF, and I'm sure that trend will continue to grow. With this and other movements such as the Maker movement, and the so called 'Internet of Things' (I strongly dislike that term), it has been opening the door to many people to use and learn about low power devices. I think there can be a lot of great things in this space for homesteaders and permies to learn.

One thing that really gets me is the cheap solar powered walkway lights. It seems there are millions of people buying these things and most of the time they don't get a year or two out of them before tossing the whole set in the trash. For people who want to create less garbage and get better value, you could buy a small panel, battery, charge controller, and lights for probably ~$250 or so and have something that isn't a disappointment. It would take more money and effort up front, but probably less in the long run (maybe 15+ years), and you would only have to replace the battery and possibly some bulbs every several years or so. It would double as an emergency power source.

I will be back at my property again this week and hopefully I can test out my LED lights some more while I am there. I will try to get some pics of the lights in action.

Led lighting is the only way to go. The power consumption is so low. I use 20 16 foot led light strips off of amazon to light my shop. 30x40. The strips are all twelve volt but my system is 24v. I wired two strips in series to run them off the 24v. Every other roof beam is varied between a warm white and a bright white so that the color of the light is more appealing. All of my lights together pull around 8 amps. I have them wired so I can run them off three light switches and only use a third at a time depending on what portion of the shop I am in.

That's a very good point about using both color lights together. I do the same thing in my house currently, but I haven't gotten that far yet with my small LED's. While the first set of LED's I bought work very well, even with little heatsinks added, the heat they produce is at the absolute threshold of what I can tolerate to touch. This is in contrast to the new set I got that barely have any noticeable heat coming from them. I think I will have to pick up another set like these in cool white and see what kind of fixtures I can come up with. The other lights are good by themselves but I wouldn't want to put multiples of them together in a fixture and risk any heat issues.

The LED strips are also a great way to go. I haven't used them personally, but I have seen them used for countless projects and they are very affordable. Having the flexibility to cut them into segments means you can either separate them for small jobs or bunch them together for better lighting in one area. I've had a lot of setbacks this week, but I'm hoping to get things sorted out and tinker with a few light fixtures this weekend. First I need to get batteries for my camera!

I did recently purchase some 12V LEDs from Home Depot. They are replacement bulbs for outdoor walkway lights. I have a 100W Solar Panel & Deep Cycle battery that I run my Aquaponics system/greenhouse off of. I plan to put those two 1.5W LED lights above the fish tanks to draw in bugs at night to feed the fish... or just for lighting to do work in there while it is cool at night.

Right now I have a small automotive/12V fan(15W), 12V air bubbler(5W), and a backup water pump(to my AC water pump if the power dies) that I run off of the system 24/7(except water pump).



Marty

I lived off-grid in an RV for two years. All lighting was LED and it did indeed function well; I was able to maintain lighting through the dead of winter using only solar generated power and a NiFe battery bank.

I learned a couple of things that will help anyone who seeks to use their 12V LED lamps for the long term.

1) You need to use constant current controllers between your battery bank/solar array and your LED lamps.

As the LED junctions heat up, they allow more current through; this in turn results in more heat, which increases the current, looping as such until the LED fries itself, begins randomly flickering, or steadily decreases in lumen potential. If you've ever seen LED lamps that had an amber or brown tinge of burn around the elements, thermal runaway was the culprit. A constant current controller accepts variable voltage input, and outputs a reliable current based on the maximum you preset on the controller. Voltage decreases as the temperature rises, keeping the total current the same and preventing the bulb from overheating.

I lost about 10 bulbs in 2 years due to thermal runaway; after installing constant current controllers, all lamps performed within spec and I've had no more failures in 1 1/2 years. Constant current controllers are only a couple bucks on eBay.

2) You can run LED lighting direct off the solar panels if you use a constant current controller.

The controllers I purchased have an input range of 9-30V DC. My 12V solar panels have an open circuit voltage of 22.1V DC. If I connect a constant current controller to the panel, and a lamp to the controller, I can get reliable indoor lighting. This is helpful if a battery bank fails and cannot be replaced.

3) You can charge USB devices and operate other low voltage DC equipment direct from your panels even if the output voltage is too high.

Yep; with a constant current controller between your panels / battery bank and your devices, you can adjust your operating voltage to fit your device. I have charged 5V USB devices using a NiFe battery bank that was charging at 17V, all without issue.

4) The optimal current to run the lamps at is different than their rated current.

LED lamps output ~100% of their rated light at the rated wattage. However; manufacturers are often overdriving the LED lamps, running them at current levels that are beyond what would be recommended if you sought long element life. They do this as a means of promoting higher specs and thus making more money. It's not longevity their after; we on the other hand recognize durability and longevity as primary benefits of LED.

LED lamps running at 60% of rated current provide ~80% of rated lumen output. This is a massive boost in efficiency; it also lengthens the lifespan of the lamps, as the LED lamps run cooler. Any idea how to get lamps to run at less than their rated voltage? Yes, a constant current controller.

The moral of the story is: integrate constant current controllers into all DIY LED lighting schematics.

Another factor you may look into is your lumen output per watt, or efficiency rating. I have seen more than a 40% swing in lumens per watt depending on bulb format, element production dates (older lamps are usually lower efficiency lamps), and COB element density. A 100 watt small format COB outputs a LOT less light per watt than a 10W large format COB. It also requires active cooling, while the large format COB can be passively cooled. Passive cooling is less energy intensive; again this means more light per watt.

Finally, the quality of COB LED lamps can be quite variable. Using a constant current controller, you can provide just enough energy to light the COB and see its performance. What you should see when the elements are at their dimmest point, is all LEDs lighting at about the same intensity across the COB. What you may see instead is some bright and some dim or unlit COB elements. Most manufacturers won't tell you, but this is a major concern. The bright spots are prone to overheating, while the dim or unlit ones are underperforming and thus limiting your lumen output. If you have strings with several dead LED elements, it is likely the lumen output will degrade rather rapidly when compared to elements that are of uniform brightness. Some of this concern can be mitigated by using a constant current controller (beating the poor dead horse, I know) because a COB running at 60% current will be less likely to experience overheating at any internal junction. Uniform output is better, but uncommon in low cost LED lamps. Note that by my experience, the large format lower wattage COB LEDs are far more likely to be uniform in brightness.