MC-E & battery pack Q

[ColW]

Hi all. I'm building a single MC-E cycle light, modifying a Cateye singleshot (IIRC) housing.
A few details,
MC-E LED vf 3.4v per die @ 700ma
Enix Li-Ion 15v 2.2ah battery
Recom RCD24-070 LED driver, 700ma (this is really a PCB based driver, but i've used them successfully on other projects)

Its a very simple setup, and although i have had the LED light up, it doesnt now when assembled.
Is my battery pack big enough ? Is that why it doesnt work ?
I know the drivers ok, ive since tested it on a XR-E setup.
Because of the small lamp housing, i intended to have the driver outside the lamp in a small housing with the switch. That can't be a problem can it ?
Just once in a while, the MC-E will fire up, so it's not fried !
Tried connections several times, no different !

I keep coming back to the battery pack :thinking: Its new, and fully charged, tested on a double XR-E setup, so no problems there.

Is 15v big enough is what it comes down to ?

many thanks for any input.

 

[herulach]

It depends on how the driver works, a lot of buck drivers will direct drive the light if theres not enough voltage, this should at least give you a dim glow.

That said yours might not, your LEDs are going to be wanting ~14.8V, and fully charged your battery is 16.8V (I'm assuming its a four cell pack) 1V is right on the borderline of the amount of headroom needed by buck drivers.

TO get round it you could wire the MCE 2S2P, although unless you can adjust the driver output you'll only get 350ma per die.

 

[ColW]

It depends on how the driver works, a lot of buck drivers will direct drive the light if theres not enough voltage, this should at least give you a dim glow.

That said yours might not, your LEDs are going to be wanting ~14.8V, and fully charged your battery is 16.8V (I'm assuming its a four cell pack) 1V is right on the borderline of the amount of headroom needed by buck drivers.

TO get round it you could wire the MCE 2S2P, although unless you can adjust the driver output you'll only get 350ma per die.

Thanks for the input herulach...
I kinda reluctantly thought the voltage was a bit too close to the vf...may have to rethink this one. I wondered if the times when it did fire up, the battery was just charged and at its peak voltage...soon to drop off enough not to light the MC-E.
I've read about wiring 2s2p...but how does that happen ? Where and how are those configurations made. Can anyone point me to any schematics or tutorials ?