How do I change XHP-70 from 6V to 12V?

I bought one of these from Simon Mau and it’s on a 6V labeled plate. I’d like to drive it with 12V. How would I do this?

Look in the LED’s datasheet. For 12 V you need different MCPCB, wired in serial. Simon’s are parallel, 6V only.
You can run XHP70 in 12V setup on Sinkpad 20mm board, IIRC.

You would have to use a 12V “plate” first of all. The emitter has actually 5 pads on the back. How you connect those 5 pads electrically determines the voltage requirement. Some of them come mounted on a board that can be used either way (6V or 12V) depending on where you solder your + and - on the board.

See here for a board you could solder that XHP-70 to. I don’t know where your location is. This is a USA vendor. But, if you need to, you can find this board at international vendors’ sites as well.

Too bad XHP-70s don’t have a 3V option … would make using them in small flashlights so much easier.

@ 3 volts the amperage draw would be higher though.

I don’t care for the 6V because unless I’m missing something 2x18650s @ 4V = 8V. Maybe it’s ok to run the XHP-70 at 8V. I have done it as a test (star screwed to a heat sink). Gets REALLY hot in just 10-15 seconds… and I mean REALLY.

That’s what drivers are for, to control the led current. The XHP-70 can handle the extra voltage just as a 3V led can handle 4V.

No matter what voltage you run it at. It will be the same because the wattage it uses will remain the same. So if you use the 6V MCPB it would be 8 volts times 5 amps (depending on how much out put you want) will equal 40 watts. Or at 12 volts it would be 12 volts times 3.5 amp will equal 42 watts. All as running at 12 volts will do is increase your run time.

My Star says 6V. Can I run it at 12V? I think the wiring to the LED is different depending on voltage.

Also, I’d think with direct drive, the power consumption would go up if I run it at 8V instead of 6V. Would it not? I guess I could put a meter on it and see if the current is reduced as voltage goes up.

Nope. Power consumption will not go up. Continued running at 8v will probably ruin your xhp.
No need for the power meter. Have a look at page 2 here XHP70 Datasheet

It is definitely wired differently for the different voltage. The voltages given are the nominal values needed to turn the LED on. You could run it at 12V if it’s wired for 6V, but you won’t get it to come on at 6V, when it’s wired for 12V. So, it’s almost like a minimum voltage requirement, except that it changes slightly with the amount of current used, ambient temperatures, and other variables.

But, as others have said, it isn’t the voltage that needs to be regulated, it’s the current. If it is left un-regulated, and connected to 12V when wired for 6V operation, it will draw too much current and will burn up. LED’s will draw more current at higher voltages and vice versa. It is possible to pseudo-regulate a LED by controlling the voltage. That’s why you can safely run a ~6V LED from a ~8.4V source, sometimes even without a driver, as long as you can effectively drain away the heat. But voltage regulation isn’t as accurate as directly controlling the current. With the proper current regulation and good heat sinking, you could run that LED at voltages many times higher than what it is “rated” for.