I’m looking to build a new helmet light and was wondering if you could offer some assistance?
I’m not really set on anything yet but I do have a 7.5v 2 cell battery I’d like to use as I prefer to have the battery and light mounted on my helmet.
I’m looking to get around 3 - 4000 lumens and prefer TaskLED drivers and Cree LED’s.
I was looking at the XPL-Hi on a quad tPad in a 2s2p configuration driven by a HBFlex. That would give me a 7.5v input, approx 24v output and could drive at 2a which would give me 1a at each LED. Does that sound right ?
Personally I wouldn’t use a boost driver at all. Wouldn’t it be more efficient to to have all LEDs parallel and run off single cell voltage values? Then you can just add cells in parallel for more capacity. Seems to be a lot of messing about boosting up the voltage just to drive serial wired LEDs.
Do you mean linear drive? But wouldn’t I then need a bigger battery?
The idea is to be able to use my current 2-cell battery as I mount it on the back of my helmet. Efficiency isn’t a main concern as I only do short night rides :+1:
Well, if you’re designing the whole light around a specific battery pack I won’t argue. I’d choose a battery pack for a specific light, not a light for a specific battery pack
I’m probably missing something here… I don’t see why it would need to be bigger, it could be smaller. Instead of two cell battery pack you could use a one cell battery pack as you don’t need to double the voltage if you are using parallel wired LEDs. What kind of battery pack do you have? I’m curious as you appear to be designing your light around this specific pack.
I’m not the best when it comes to the electronics….making housings is where I’m best…
I like the 2-cell battery as I can mount it to the back of my helmet easily and it doesn’t weigh too much. I was running it with 2 x XML with an LFlex but I want to do something new.
How would you go about it if you were to be using a 2-cell battery? So if I’m coming across as a bit dim, I am :person_facepalming:
As you’re looking at a 2s2p LED configuration, I just would drop the boosting up to 24V. The 2s2p LED configuration you’re interested in should run just fine from the 7.5v output of your battery pack as they are 3V LEDs. No need to boost voltage up to 24V. There are plenty of driver options for that kind of operation.
Hmm… Gotta say I’m a little confused now. Checking the info in that link I read this:
Parallel, means 3 Volt opertation but you would require 4 x normal current as parallel divides in half for each led in the string ie 4 amp driver will deliver 1 amp per led. Series leds will need 12V and will deliver drive as per driver to each led Series/parallel is a hybring of the two above, so typically the board would be 6Volta and the drive current will be halved
They can’t suggest 3 volt operation (parallel) with 12 volt LEDs, that makes no sense, but looking at the datasheet they linked to the forward voltage of that LED is over 11 volts.
Electrically simplest would be 2s2p LEDs run from a Zener modded Qlite linear driver from 2p cells or a bflex from 3s cells. The Maxflex used to be an option but Georges reduced output from 1300mA to 1200mA then removed it from the active list. I use old Vistalite housings with cute-3/4 optics and add a bit of copper. The VL 500’s have both handlebar and helmet mounts.
