Taskled Hyperboost 2.0 Driver with xm-l's

I've got a hyperboost driver that I'm trying to drive 5 cree xm-l's with. I've got them wired in series. I want to power it with a small 12 volt battery. Now from what I see, the xm-l's need an input voltage of 3.3v each. So the driver needs to put out 16.5 volt. From what my multimeter is telling me, there's about 90 volt of output. I'm sure I've fried the led's. What am I going wrong here?

Did you power the driver before connecting it to the LEDs?

The 90 Volts is the open circuit voltage of the driver. If you are measuring it when the leds are connected, than something is blocking the current (fried LED, reversed polarity of the LED(s)).

If it is disconnected, this is normal operation.

Verify that all the LEDS are connected the right way. Fried LEDS are visibly damaged most of the times, so if they look normal (no brown touches inside the lens) they probably are.

Edit: and what AppleSnails says. If you to that with a boost driver, this will result in a high voltage which might kill the leds due to the high inrush current.

The leds were connected before being the battery. They dont appear to be fried. The voltage measured 90 with the leds connected. Could it be poor solder connections?

maybe wrong polarisation of the led´s ?

Something is preventing current from flowing. The LEDs are backwards or you have at least one (very bad) solder joint somewhere. Check them all, possibly using your voltmeter to lock down what is or isn't connected.

you can easily test leds with a volt meter by setting it in diode mode and put thered probe to the plus and the black to the minus. if the led lights up slightly, it's ok. then move 1 of the probes to the other side of the wire that you soldered to that led and test again. If the led doesn't light up, your problem is the soldering of that wire.

Next, put your voltage probe on the supply wires of the driver. Keep the negative in contact, and 'step through' each LED until you get no voltage. Now you've found (one) bad solder joint.

I tested the leds with a 3 volt battery and found that only 2 of them are functional. Should be getting another 6 xm-ls next week.