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Open Roads Forum  >  Do It Yourself Modifications and Upgrades (DIY)

 > Cheap LED light bulb review

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Gdetrailer

PA

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Posted: 08/06/11 06:25pm Link  |  Print  |  Notify Moderator

Harvey51 writes "What fails? Is it the LED itself or supporting electronics?"

Both can fail, but often enough it is ONE LED which can take out the entire light or one section of the light.

The problem stems from manufacturers PUSHING the LEDs too far without providing a good way to dissipate the buildup of heat from the LED junction. Most fixtures tend to use plastic encased LEDs which depend on the leads to dissipate the heat. Manufacturers tend to cut the leads short and solder direct to the circuit board. The circuit board then must act as a heat sink.

Some manufactures use surface mount LEDs, these too must depend on the circuit board to dissipate the heat. Put enough LEDs together in a small space and the heat has nowhere to go.

White LEDs are often placed in series strings of three each for 12V lights so if one LED light burns out then that means one string goes.

LED lights without built in regulators are at risk from RV converters providing too high of a voltage and the ones with regulators (which are switching regulators) tend to put off a lot of RF energy causing radio interference.

I have had better luck with a single high power LED flashlight than any multi LED flashlights. Why? Well the high power LEDs have a BETTER design for a heat sink.

Better LEDs tend to be the high wattage ones not the ones with 20 or 30 fractional watt LEDs but they cost a heck of a lot more than most folk are willing to pay.

To me, you are not saving any money with LEDs, it is over hype of the green people. Most LED lights are not able to deliver 100 Lumens per watt as claimed by the manufacturers, a good fluorescent light is able to reach and exceed 100 lumens per watt and cost a fraction of LEDs.

A lot of folks here seem to love LED lights but for myself the honeymoon with LEDs are over they do not last and are way overpriced per lumen and I will not buy any more.

FaireCat

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Posted: 08/07/11 12:35pm Link  |  Print  |  Notify Moderator

Some interesting experiences here. We have over 30 LED fixtures in our house - mostly CREE CAN retrofits, but some LED Wholesalers MR6 bulbs (5), some regular socket bulbs and even some T5(? - several foot long flourescent tube) replacement. All but the tube we've had well over a year. Zero failures. One replacement, that to a dimmer fixture over a computer on a circuit shared by several.

We're new to our RV, but I've had a lot of automotive LEDs with zero failures. I don't expect many in the RV either... though if it happens, the -usual suspects- are not the LED manufacturing.

The big one is voltage transients (spikes) - like when a motor goes on and off. That kills them fast, and it's really common to systems that have a charger charging while devices are running off the power. The other big one is polarity reversal... diodes just can't handle that, even for a moment. So if you do any work on your rig and let the wrong wires touch together, it can be a very expensive mistake. They can over-heat and die also, but it isn't likely in environment that previously handled incandescents safely.

Gdetrailer

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Posted: 08/07/11 08:21pm Link  |  Print  |  Notify Moderator

FaireCat writes "Some interesting experiences here. We have over 30 LED fixtures in our house - mostly CREE CAN retrofits, but some LED Wholesalers MR6 bulbs (5), some regular socket bulbs and even some T5(? - several foot long flourescent tube) replacement. All but the tube we've had well over a year. Zero failures. One replacement, that to a dimmer fixture over a computer on a circuit shared by several."

Cree=not cheap, should be fairly good since most cree designs use seperate heatsink connection from the electrical. Gives them a fair chance to live a long life. But you pay for that life.

I looked at T8 retrofits for home, not in my price range at $50-$70 for ONE 4ft 20W bulb (by the way only gives 1200 lumens which is half of a 34W T8 fluorescent bulb which only costs $1.50 each. Just no comparison.

"We're new to our RV, but I've had a lot of automotive LEDs with zero failures. I don't expect many in the RV either... though if it happens, the -usual suspects- are not the LED manufacturing."

Naive to say the least, the manufacturers are pushing the current limits (which pushes the heat) in order to pump up the lumens so it is a trade off of life to pump out more light.

"The big one is voltage transients (spikes) - like when a motor goes on and off. That kills them fast, and it's really common to systems that have a charger charging while devices are running off the power. The other big one is polarity reversal... diodes just can't handle that, even for a moment. So if you do any work on your rig and let the wrong wires touch together, it can be a very expensive mistake. They can over-heat and die also, but it isn't likely in environment that previously handled incandescents safely. "

Not buying it, LEDs are diodes, and diodes have no problem with voltage reversal in fact LEDS have very good reverse voltage capability. If transients and spikes are causing the failures then every device I have ever owned with LEDs should be dead, not so, only the white LED bulbs I have bought which are more than night lights just can't hang with the big boys.

My conclusion with White LEDs is they are not much better than night lights and flash lights.

My suggestion is most folks have inverters, dump the overhead lights and grab a couple of home lamps and plug a 9-13W CFL into the inverter. You will get much more light at a lower cost and it WILL be reliable!

Dave-Sparky

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Posted: 08/08/11 01:05pm Link  |  Print  |  Notify Moderator

I have also been looking into these LEDs from Hong Kong that are for sale on e-bay.

">EWNX:IT]Warm White LEDs

I bought one batch of 10 abut a month ago and they seem to be working great, so I ordered a second batch of 10 to finish the change out and have a few spares. Some of the comments about failures and such got me to wondering. And as my wife will tell you, "there is nothing worse than an engineer with a technical question".

I looked up the data sheet LED Specs for the LEDs that were used to build these panels and then I took one apart to "check it out". What I found was actually very well done.

the 36 LEDs were connected in 12 groups of three with an individual series dropping resistor on each group.

I then tested the assembly with the following results.
[image]
[image]
There was no visible light until the voltage reached 7.0 volts and no measurable current until 8.0 volts was reached.

Since there are 12 strings of LEDs on the assembly I took the maximum rating from the data sheet of 30 ma per LED times the 12 strings to get a maximum current for the assembly to be 360 ma.

Looking at the chart that equates to just under 14.5 volts applied to the unit under test.

It would appear that any of the normal charging voltages that could be applied should not harm the LEDs. This is a very good thing. You cal also see that the unit withstood a maximum voltage of 17 volts without damage. It looks like these are actually designed for the application we need!!


Dave


Dave and Colleen
Colleen's Beach House
1991 Dutchman TT 24FK
2007 Chev Avalanche AWD


FaireCat

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Posted: 08/08/11 03:39pm Link  |  Print  |  Notify Moderator

Gdetrailer wrote:

FaireCat writes
"We're new to our RV, but I've had a lot of automotive LEDs with zero failures. I don't expect many in the RV either... though if it happens, the -usual suspects- are not the LED manufacturing."

Naive to say the least, the manufacturers are pushing the current limits (which pushes the heat) in order to pump up the lumens so it is a trade off of life to pump out more light.

I'm a bit surprised by the aggression in your post. These aren't "no name" units, and I have a lot of experience in the field, just not in RVs.
Gdetrailer wrote:

FaireCat writes
...The other big one is polarity reversal... diodes just can't handle that, even for a moment. So if you do any work on your rig and let the wrong wires touch together, it can be a very expensive mistake. They can over-heat and die also, but it isn't likely in environment that previously handled incandescents safely. "

Not buying it, LEDs are diodes, and diodes have no problem with voltage reversal in fact LEDS have very good reverse voltage capability.

Okay, let's do a Google for a spec. I searched for 12V LED "reverse voltage" spec sheet. The first sheet I got was this one (clicky). As you can see, the Forward Voltage is 12V but the Reverse is 5V. Exceed that and you get "Breakdown".

The next was this one with the same specs essentially. And the third was the DiaLight 521-9183, which has a 7.5V forward and 5V reverse voltage (not clear on why it came up in a 12V search.) And the LEDTech UT18W2-4D-URC3-12V 5.0mm, which is also 12V forward, 5V reverse.

So the typical 12V LED cannot handle even half that in reverse voltage. Yes, there are some very expensive LEDs that are essentially two LEDs with very high "breakdown" voltages that can handle AC, but the way they work is to block the reverse current (i.e. have a high breakdown) and combine two of these - one each direction. And you'd be unlikely to find them in an RV for last of cost-justification.

phlyphyshr

Quiet corner

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Posted: 08/09/11 07:13pm Link  |  Print  |  Notify Moderator

I don't know about everyone else, but I didn't switch to LED's to save money, I switched to save voltage/amperage! We are off of the grid most of the time and incandescents suck a lot of juice.

Please note, as well, we only paid about $2.50 a bulb and I have extra's. With all the expenses of maintaining a TT, if I have to replace them every two years, they're still a bargain!

If folks spent as much time coming up with positive suggestions as they do with finding fault, this site would really be awesome.

* This post was edited 08/09/11 07:21pm by phlyphyshr *

BarneyS

S.E. Lower Michigan

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Posted: 08/09/11 07:41pm Link  |  Print  |  Notify Moderator

phlyphyshr wrote:

Snip...
If folks spent as much time coming up with positive suggestions as they do with finding fault, this site would really be awesome.

I think it is not so much finding fault as it is sharing experiences - both good and bad. That is what the forums are for.
Barney


2004 Sunnybrook Titan 30FKS TT
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Gdetrailer

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Posted: 08/10/11 06:41pm Link  |  Print  |  Notify Moderator

Phlyphyshr writes “I don't know about everyone else, but I didn't switch to LED's to save money, I switched to save voltage/amperage! We are off of the grid most of the time and incandescents suck a lot of juice.”

I never said about LEDs saving money, did I?

In fact I mentioned that LEDs are much more expensive, give off less light than OTHER lighting (mainly fluorescents). No one can deny that incandescents waste a lot of energy in the form of heat but fluorescents STILL out produce even the best White LEDs at this time from not only REAL WORLD (not hype) lumens per watt but even at price points.

Instead of spending $200-$300 on LED lights which MIGHT save you on average of .7Ahr per fixture (single bulb) for 1 hr x say 20 fixtures=14Ahr if all were on for 1 hr, you could add one pair of 6V GC batts for $140 and gain 105Ahr of usable capacity. Sure there will be a small tradeoff of a little more gen time but it really shouldn’t be much of an issue.

I have as of yet found any white LED product that actually lives up to the lumens rating they give, most are half or less the brightness when compared in real life. Example, one LED bulb I had was 5W, the rating they gave was compared to 45W incandescent. In real life it was no brighter than a 15W incandescent (it in no way shape or form could replace a 40W incandescent bulb like the LED manufacturer CLAIMED.

Someone else on this forum in another posting had mentioned before the idea of using 9W-13W 120V CFLs in several home light fixtures (desk lamps or even wall sconces) in their RV using an inverter (you can in fact even buy 5W CFLS!!). This is a much better way to go instead of trying to retrofit the cheap 12V RV fixtures which are often placed less than ideal anyways.

Most folk are going to have a small inverter running just to power their “entertainment” items like PCs TVs, sat receivers so plugging in a 9W CFL in to an inverter is not wasting any power, in fact it gives much more light than most RV light fixtures could possibly give. Heck many inverters only use .5Ahr of battery with no load, might as well make use of the inverter. An additional benefit is the low cost of CFLs now days, $2 and it will outlast any cheap LED (I have easily gotten 10+ yrs out of CFLs).

Just so you know, while I don’t generally boondock for days on end, I do overnight without power, with a twist. The twist is my TT has a 120V home fridge retrofit, I use an inverter which turns on/off with the fridge demand and one pair of 6V GC bats. This typically gives me enough capacity to overnight easily using the RV furnace and a couple hrs of 20W 12V halogen under cabinet puck lights I also used to replace the miserable 12V RV fixtures and still have some capacity leftover by morning.

I found that one 20W 12V halogen under cabinet puck light could give almost the same amount of light as the 12V RV double light fixtures! By replacing bad designed 12V RV light fixtures with better designed home fixtures I need less fixtures turned on to give me enough light. I also have a mix of 4W and 8W drycell fluorescent fixtures I retrofitted to use 12V sprinkled around in key locations to boot.

Granted, I am not running computer, surround stereo or 42 inch plasma TV during my overnighting but I would think that most folk should be able to operate for 1-2 days between charging on one pair of GC batts without the need for extreme things like LED lights.

I am not trying to be negative, but I am giving my real life experiences. I gave LEDs a try, they failed miserably and now I am trying to prevent folks from LISTENING to marketing double speak hype and perhaps making a better informed choice by thinking outside the RV box…

Gdetrailer

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Posted: 08/10/11 02:43pm Link  |  Print  |  Notify Moderator

Fairecat writes “I'm a bit surprised by the aggression in your post. These aren't "no name" units, and I have a lot of experience in the field, just not in RVs.”

No aggression is meant, since you mentioned Cree, I acknowledged that THOSE should be of decent design which INCLUDES a real means of heatsinking the LED modules separate from the leads. Most typical low cost white LED lights do not use Cree LEDs and may not be as good quality. If you look at your Cree home light fixtures you will notice that the bulb typically has aluminum ribs. Those ribs are not decoration, they ARE the heatsinks for the LEDS, LEDs do waste some energy as heat and it must be pulled away from the diode junction. Failure to do so results in short life.

My point is LEDs and LOW COST do not exist in the same world together, if you go cheap, expect very little, go expensive and expect a small amount better than cheap but ultimately White LEDs are no more efficient than fluorescent lights but cost many, many times more than fluorescents.

“Okay, let's do a Google for a spec. I searched for 12V LED "reverse voltage" spec sheet. The first sheet I got was this one (clicky). As you can see, the Forward Voltage is 12V but the Reverse is 5V. Exceed that and you get "Breakdown".”

Sorry, no such thing as 12V LED lights, there is no SINGLE LED that directly operates at 12V, a LED light that is rated at 12V must be either in series with other diodes, a resistor or a specially designed current source driver (IE switching power supply) in order to not exceed the forward voltage and current rating.

I suspect that the LED you linked to is a single LED with a series dropping resistor which when in reverse voltage condition would provide more than 5V to the LED (resistors have very little voltage drop when no or very little current is drawn which would be the case in this example).

Each LED has a forward voltage and current rating which is the condition that makes the LED emit light. Each LED also has a reverse voltage which is the voltage that the diode will block or not conduct any current.

OK, so let us look at real word FACTs directly from Cree and not google?

Per Cree HERE

For 1W Xlamp White LEDs...

“DC Forward Current - white ? 5000 K, royal blue, blue mA 1000
DC Forward Current - white < 5000 K, green mA 700
DC Pulse Current (@ 1 kHz, 10% duty cycle) A 1.8
MAX Reverse Voltage V 5
Forward Voltage (@ 350 mA) V (Typical) 3.3 (Max)3.9
Forward Voltage (@ 700 mA) V 3.5
Forward Voltage (@ 1000 mA) - white ? 5000 K, royal blue, blue V 3.7
LED Junction Temperature* °C 150”


So, with a white LED you will have 3.3V-3.9V FORWARD voltage PER LED. For 12V LEDs typically 3 are in series for 9.9V- 11.7V (voltage stacks in series) range and still would need either a small value resistor or a switching regulator to limit the current draw through that string. Typically for home fixtures 10-15LEDs are in a string along with a voltage dropping resistor (since they are diodes they only conduct in one direction).

Notice that the MAX REVERSE VOLTAGE is 5V PER LED so for a typical 12V LED light you will have a series string of THREE LEDS which gives you 15V Reverse voltage for your 12V light not 5V as you mentioned.

The rub starts with any 12V Led fixture which may have a switching regulator… The regulator may not take kindly to reversed voltage conditions and therefore may let out the smoke packets and no longer work.

By the way the specs from Cree are very similar to ANY “white” LED, old school low power LED colors Red, Green, Yellow are typically 1.2V-1.7V forward voltage with typical current of 15ma-20ma. White and Blue colors are treated much differently, they use UV light to “excite” a phosphor coating.

I have even gone as far dissecting my failed LED lights, from doing so I was able to conclude that the manufacturers are indeed pushing the absolute max electrical ratings in order to squeeze out as much light out of low cost LEDs. This is a shame, by simply reducing the current (there by reducing the heat generated by the junction) by say 5% it would not be very noticeable in lumens but would extend the LIFE of the LEDs considerably.

Another dirty secret that no one here is willing to talk about is that white LEDs get DIMMER over time. For this reason some manufacturers attempt to compensate by using a constant current source (IE switching power supply) to reduce this effect. I have had several 120V Led nightlight bulbs (in dusk to dawn fixtures) over one year of average 12hrs per day on time they tend to lose easily HALF the brightness and after two years are completely useless (that’s about 8,000 hrs!!!). I have repeated this on different brands of white LED night light bulbs with the SAME results.

FaireCat

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Posted: 08/11/11 03:43pm Link  |  Print  |  Notify Moderator

Gde, do you actually work (as a profession) with LEDs? I used google as a reference you could easily understand and utilize, but I have years of real-world experience designing them in, bringing boards up, etc. Had you spent a few seconds doing a similar search on Mouser (one of my suppliers when not working directly with Arrow and AVNet), you would have found many other examples, such as http://www.ledengin.com/files/dist/10wLZ/LZ4-00B210.pdf

I provided links to spec sheets, on third-party respected sites showing that many Vf-12 LEDs from respected suppliers have Vr==5. Don't tell me why it doesn't make sense; that lacks credibility. Prove to the world that the manufacturers have under-specified their Vr and explain what benefit they derived from doing so.

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