i want to operate them at their max current. from what i see on the sheets their min is 250mW and max 350mW so yeah sorrry
it would be 1400ma.
i got it from here https://www.mouser.com/ds/2/90/XLampXPE-221789.pdf
for the XPEFAR-L1-0000-00701 cobs

Where, exactly, in that data sheet do you see minimum and maximum power of 250 mW and 350 mW?

For the far red LED, the maximum current is 1000 mA. If the LEDs are in series, then the SAME 1000 mA that flow in one will flow in all of them. The data sheet only gives a typical forward voltage of 2.25 V for this case, but based on the other data you can probably expect the actual voltage to be up to 500 mV above or below this, so perhaps as much as 11 V and as low as 7 V, but more likely somewhere between 8 V and 10 V.

As has been pointed out several times, it is generally NOT a good idea to operate LEDs at their max current. But you seem insistent on doing so. Just don't be surprised if they don't last as long as you think they should, particularly if you don't heat sink them very well.

A 12 V DC supply that can deliver a minimum of 1 A should work. You'd be better off with one that can deliver 2 A because it will run cooler when delivering 1 A than a 1 A unit will when being run at its max. A 15 V DC supply will let you control the current more tightly, but will also waste more energy.

 

I think that i can power 4 of these leds with
MEAN WELL LPC-35-700

 

I think that i can power 4 of these leds with
MEAN WELL LPC-35-700

Yes but not at the maximum drive the LEDs will handle which is probably a good thing.
SG

 

Mouser sells stuff but knows nothing about the spec's.
The LEDs have a range of forward voltage and maybe none or a few will be 2.1V.

Did you find out anything about how big must the heatsink be for 350mA continuously?
Cree says they test them at 350mA when the case is cooled somehow to room temperature but maybe the test is for only a moment then the LED does not heat up.

 

The LEDs are rated for 350mA and the 48V/700mA power supply will blow them up with double their rated current. The power supply produces up to 48V but you need only 9V or 10V for 4 LEDs in series.
If you find a proper power supply then how will you cool the LEDs??

 

The LEDs are rated for 350mA and the 48V/700mA power supply will blow them up with double their rated current. The power supply produces up to 48V but you need only 9V or 10V for 4 LEDs in series.
If you find a proper power supply then how will you cool the LEDs??

The OP is using a different LED then in his original post. See post #20.... Geezzz.
SG

 

Glad I'm not the only one...

What I want to know is how is he going to mount those things.

 

Ill mount them with thermal paste on a 45cm x10cm heatsink 5cm thick

 

Well there is more to mounting that type of LED then just pasting it to the heat sink.

You will also need to create a hard point/s for strain relief, and connect the higher gauge wires to, and then run lower gauge to the LEDs, from there.

 

What do you mean strain relief? Cant i use any gauge?