cheack my LED/driver math please

[mkj]

I'm working on my RB string using Cree XTE and a Meanwell LPF-90D-54V driver/PS. I'm looking at two options for this driver. (option1)Two parallel strings of 24 LEDs or (option2) one string of 18 LEDS. Do both of these options work?

Info:
Cree XTE RB max current 1500Ma (@700Ma 3.0v)
Meanwell LPF 90D-54v-1.67A CC range 32.4-54v (over voltage of 59-65v) http://www.meanwell.com/search/LPF-90D/default.htm

Option 1: 12 x 2 array uses 24 LEDs
Is it correct that by using two strings my 1.67A would split into 835Ma for each string?
The total voltage is around 36v for each string which is within the CC range for this driver. Wattage would be 72w



Or if I dropped to 18 LEDs on one string would the amps be too high or does the LPF adjust for this?

Option 2: 18 x 1 array uses 18 LEDs
54 volts (which is at max but there is an overage of 59-65v for the LPF so I think I'm still ok)
54 watts total for single 18 led string.

If they both work then I will just have to decide which one to go with.

 

[mcgyvr]

Info:
Cree XTE RB max current 1500Ma (@700Ma 3.0v)

Option 1: 12 x 2 array uses 24 LEDs View attachment 243706
Is it correct that by using two strings my 1.67A would split into 835Ma for each string?
The total voltage is around 36v for each string which is within the CC range for this driver. Wattage would be 72w



Or if I dropped to 18 LEDs on one string would the amps be too high or does the LPF adjust for this?

Option 2: 18 x 1 array uses 18 LEDs View attachment 243707
54 volts (which is at max but there is an overage of 59-65v for the LPF so I think I’m still ok)
54 watts total for single 18 led string.

If they both work then I will just have to decide which one to go with.

Option 1: In a perfect world they would share the current equally.. This aint a perfect world.. Google "led thermal runaway".

Option 2: Too many amps as 1.67a>700ma. Unless you keep it dimmed below 50% all the time. Also too many LED's in the string. The sum of the forward voltages may be too high (again unless you keep it dimmed below 50%)

IMO neither option is a good one. I would do option 2 with a meanwell LPF-40D-54

 

[mkj]

thanks mcgyvr, I didn't think the LPF needed a resistor, I thought it had a self sensing circuit, where as the ELN needs a variable resistor (potentiometer). I'm very new to this so more research for me I think.

I am trying to do what Sebyte(steve) did here, starts 3rd post down on page 2, he has several post on topic in the thread http://forum.reefangel.com/viewtopic.php?f=2&t=788&start=10

but using 24 LEDs. I think steve used 28 (he also is using the LPF). He states that most people tend to use way too many PSs than they need and he has 40 years in the electrical business. So I'm trying to emulate what he did "somewhat" but I have very little experience. I also have the reefangel+ PWM on the way, which is what steve is using as controller. Thanks for any help

 

[mkj]

NM this article helped me http://www.reefcentral.com/forums/showthread.php?t=1882365