Driving at 2100 and Help With Math

[sunny747]

I see some kits driving at 2100 ma. From what I gather this is not the best idea and it's better to drive at lower amperage, right?

Are you just giving up some efficiency and picking up heat to save a little money in build?

This DIY kit or example.. (Help me with the math if I do this wrong)

http://www.rapidled.com/vero29-triple-cob-array-kit/

Draw 260 watts:

The Cobs:
They use 3 vero 29 Cobs. I believe these are 36 volt. (Meaning it takes at least 36 volts per cob to power them)

The driver:
Mean Well HLG-240H-C2100A
59-119V DC output (2-3 VERO29/CXB3590 COBs, or ~20-39 regular LEDs

Breaking this down we know tht the VERO and Cree cobs are 3 volts and this driver can supply up to 119 volts, correct? So we can only fit 3. 3 x 36 = 108 volts.

This means that each cob is running at (119/3) 39.6 x 2.1 or 83.3 watts per cob.. Is this correct?

That gives us 249 watts,, 39.6 x 2.1.


I guess this is the question.. disregarding build price, there are better ways to build a 250 watt Cob light, right?
Running 5 cobs at 1400A and 179v would seem more efficient and give a better spread, right?

 

[CobKits]

is a cost balance.

more cobs= more money upfront=higher efficiency in the long run and you may or may not see that return

certianly theres nothing wrong with it. many cobs are rated for well over 4000 mA

 

[CoB_nUt]

I see some kits driving at 2100 ma. From what I gather this is not the best idea and it's better to drive at lower amperage, right?
?

I'm wondering why this amperage isn't the best idea. Or is just for this particular instance a 250 w cob bar/light. Just wondering if it's the amperage because I just purchased a MW HLG 320-c2100b. For my latest baR to run 4 Cree 3500k. For about a 320w bar.

 

[sunny747]

I'm wondering why this amperage isn't the best idea. Or is just for this particular instance a 250 w cob bar/light. Just wondering if it's the amperage because I just purchased a MW HLG 320-c2100b. For my latest baR to run 4 Cree 3500k. For about a 320w bar.

For the Cree you are just driving them a bit hard I think.. It'll work fine, but you give up some efficiency and pick up some heat... I think.. Take nothing I say to be accurate or true Maybe you need to consider an active heat sync or something? I'm not sure.

4 cree cxb can be put on an hlg 185 1400 which is a cheaper driver and better suited, but it's 200 watts.

Running these at 80w you may be cranking out more ppfd than is necessary... I reallly don't know. Just a thought. If you ran 1400ma with more cobs it would be more efficient. Better spread.. But it's a cost/benefit situation..

 

[sunny747]

I'm wondering why this amperage isn't the best idea. Or is just for this particular instance a 250 w cob bar/light. Just wondering if it's the amperage because I just purchased a MW HLG 320-c2100b. For my latest baR to run 4 Cree 3500k. For about a 320w bar.

I find the combos put together by the DIY kit companies always seem to make the most sense.. They are pretty good at pairing things together.

 

[sunny747]

Meh.. what do I know... Here is the same combo on Timber.... If they put it together then I'd say it's all good in the hood.

http://timbergrowlights.com/300-watt-cree-cxb3590-square-framework/

 

[coolj]

my thing is, buy the biggest driver for the cobs you can find, YOu can always dim it.

 

[CoB_nUt]

For the Cree you are just driving them a bit hard I think.. It'll work fine, but you give up some efficiency and pick up some heat... I think.. Take nothing I say to be accurate or true Maybe you need to consider an active heat sync or something? I'm not sure.

4 cree cxb can be put on an hlg 185 1400 which is a cheaper driver and better suited, but it's 200 watts.

Running these at 80w you may be cranking out more ppfd than is necessary... I reallly don't know. Just a thought. If you ran 1400ma with more cobs it would be more efficient. Better spread.. But it's a cost/benefit situation..

understood, I already have 2 of the 200w bars. 4- cxb3500k on mw185-1400. Maybe I didn't quote or phrase my question correctly. I did find an answer in your responses. Thank you.

 

[modeler]

Rather stupid question

HLG-185H-C700A outputs 119V
3x 3590 require 108V


So if we use only those three COBs on that driver, the remaining Volts (11V) spread across them COBs ?
So effectively those COBs eat 39.6V/COB



This sounds normal ?



EDIT: Im complete n00b on this territory BTW

 

[alesh]

Rather stupid question

HLG-185H-C700A outputs 119V
3x 3590 require 108V


So if we use only those three COBs on that driver, the remaining Volts (11V) spread across them COBs ?
So effectively those COBs eat 39.6V



This sounds normal ?

No, the driver will limit voltage to a value that's needed to pull 700 mA through the circuit which would be around ~100V with 3x CXB3590.

edit: HLG-185H-C700A outputs 286V max, though.

 

[modeler]

Shiat, I meant Mean Well HLG-240H-C2100A.


My bad for mix up. But then the OPs analogy is wrong ? Or did I fu*ked up something ?


Tnx for the info btw

 

[CoB_nUt]

eh.....still not sure why driving at 2100 isn't a good option. Hope I didn't purchase the wrong driver.

 

[alesh]

eh.....still not sure why driving at 2100 isn't a good option. Hope I didn't purchase the wrong driver.

It will work. Just saying the driver will adjust its output voltage to a value that's needed to pull the needed current through.

@2100 mA
3x 36.11V for CXB3590s
3x 37.6V for Vero29-Ds

 

[CoB_nUt]

thanks alesh, I meant I'm hoping I didn't purchase the wrong driver just due to it's efficiency/efficacy? Compared to the others I have,185-1400. Also, I am running 4 cxb 3590 on the 320-2100. My apologies, I didn't specify which one.

 

[BobCajun]

All you need to do is turn the current down to increase efficiency. It has screws to adjust voltage and current, right?

 

[CoB_nUt]

Yes Bob, I have a pot and resistor attached. Just wondering, because I don't see that driver used much. Or I haven't read enough threads. Not too worried about the 1 bars efficiency. I have two other 200w bars @56%. Thank you.