[POLL] COB LED Lifetime? Installation and service questions..

• [POLL] COB LED Lifetime? Installation and service questions..
  Posted by Zucca on 06 Sep, 2017 10:49
• Hi Gents,
  
  I got those 600x6 mm 20W COB LED strips, and I am planning to use them in a kitchen.
  
  This ones:
  
  https://www.aliexpress.com/item/Sumbulbs-60cm-40cm-30cm-COB-Chip-Light-Bar-Lamp-LED-Strip-Lamp-Bulb-20W-DC-12V/32794480448.html?spm=2114.search0104.3.1.Toe4RD&ws_ab_test=searchweb0_0,searchweb201602_5_10152_10065_10151_10068_5490020_10193_10194_10304_5550020_10307_10137_10060_10302_10155_10154_10056_10055_10054_5470020_10059_9911_100031_10099_5460020_10103_10102_10052_10053_10142_10107_10050_10051_10320_10321_10322_5380020_10326_10084_10083_10080_10082_10081_10177_10110_10111_10112_10113_10114_10180_10312_10313_10314_10184_10319_10078_10079_10073_10186-9911,searchweb201603_1,ppcSwitch_5&btsid=48e32981-81be-45bb-be47-743b50044d4b&algo_expid=d9c86e4a-fe8c-4e1a-ba76-24b58c370bd8-0&algo_pvid=d9c86e4a-fe8c-4e1a-ba76-24b58c370bd8
  
  now, for aesthetic reasons I want to place them in a very hidden place glued with epoxy to an aluminium U profile (which will act like a heatsink...).
  
  They are rated to MAX 1500mA, I am planning to run them at 1A or so.
  I am expecting they will last forever (>7years) so who cares about replacing them...
  
  Do you have any experience with such devices? I know it will be better to place them where is also easy to replace them in case something goes wrong... but it is really needed? I mean they are COB LED not prehistoric bulbs...
  
  I would like to hear your opinion... Thanks in advance....
• #1 Reply
  Posted by Zucca on 06 Sep, 2017 11:37
• From google:
  
  http://www.mastergrowled.com/Resources/How-to-Ensure-the-Lifetime-of-Your-COB-LED-Grow-Light/
  
  https://www.digikey.com/en/articles/techzone/2014/mar/why-and-how-chip-on-board-cob-leds-reduce-cost-and-save-energy-in-lighting-designs
• #2 Reply
  Posted by krystian on 06 Sep, 2017 11:49
• If you're going to glue them to heatsink and lower the current they should work forever, if you will power them from decent power supply. My friend had LED strips in kitchen with chinese power supply and it killed them after a week.
• #3 Reply
  Posted by sleemanj on 06 Sep, 2017 12:05
• You are buying them from Aliexpress so you should probably just assume they will fail. 
  
  At the very least if you get one of the die develop a dicky bond wire you end up with an annoying "flicker" in light output and want to replace it.
  
  You should at least to do a "soak test" before final installation to at least avoid bad-from-factory ones, and actual measure your thermal performance to ensure it's not terrible. 
  
  
• #4 Reply
  Posted by Zucca on 06 Sep, 2017 12:12
• Quote from: sleemanj on 06 Sep, 2017 12:05

  "soak test"
  

  
  Sure a soak test is a MUST with all the chinese stuff. Where do you buy COB lights normally? Is Aliexpress so bad?
• #5 Reply
  Posted by Zucca on 11 Oct, 2017 10:53
• The officer the the german custom warned me those china LED can set a house in fire, and to be carefull   
  
  So I finally installed those ones and stick them to an aluminium L profile (about 20mm X 10mm and 1,5mm thick)... I placed them on the 20mm side.
  
  Everything works. They are sucking about 1,2A after warming up (<1,5A max)@12V so about 15W (<20W MAX)... each strip.
  
  The strip end where the wire are soldered is the hottest spot in the strip...of course.
   
  Since I needed two of them I place the two soldeirng ends close to each other at the center of the alu profile.
  In this way  I reduced the amount of wire needed, I made a little Y cable and soldered the two strips. Something like this:
  
                                              12VDC PSU
                                                     I
                                                     I
  XXXXXX LED XXXXXXXXXXX----- Y wire----XXXXXX LED XXXXXXXXXXX
  
  I left the LED running for 2/3 hours ... when I came back I touched the middle of the alu profile just in where the Y cable center is: results, i can hold my finger on  it but it to me it was very hot,  like 40-50° my guess. According to the specs: LED Chip < 115°, Aluminum bar<70°C, silicone glue <90°C), so it should be ok...
  Interesting enough the both strip end on the other side (not the soldering one) were cold...
  
  Ambient temperature was 20°, again my guess.
  
  Comparing the cold state vs hot state I obseved no discoloration or any light LED issue.
  
  What do you think??
  
  Maybe I put a R in series, since the lux amount is just way above what I need, but indeed it is nice to have  ...
  
  PS: Temped to run those LED like this as an experiment. I would like to investigate what will happen.
  PSS: if you guys are interested I can do some measurements with a thermocouple....
  
  Thanks in advance!
• #6 Reply
  Posted by Zucca on 12 Oct, 2017 21:15
• Got some temperature tonight:
  Max T at the alu heat sink was 55C@25C room temperature.
  
  So I will leave leave like this.
• #7 Reply
  Posted by Zucca on 13 Oct, 2017 16:30
• Thanks blueskull, looks like you know the stuff.
  
  According to the Specs, those are the limits:
  LED Chip < 115°, Aluminum bar<70°C, silicone glue <90°C
  
  I am measuring 55C (+30C above room T) right on the hottest spot (just on the side where the COB strip begins) at the Alu heatsink... so I see no problem..
  
  Maybe 45C with a bigger heatsink would be a better choice, but I want to run this configuration to see what will happen in the future.