This was something I started looking at a while ago and at the time was looking for a 1 mode driver that could support 12v input. But I couldn’t see one, so parked the idea.
However on reflection, would I even need a driver? People direct drive XM-L’s on li-ion power. So is there maybe a simpler and cheap way of reducing the voltage down on a car and simply wire in a switch & relay in the mainbeam part of the loom and run an XM-L spot lamp that way?
Thanks.
a big power resistor is the simplest option, although you’d be dumping a huge amount of heat dropping 12-14V down to 3V, so most people that consider this go for triples or quads.
As for drivers, you’re best of trying to find one with a very high input voltage tolerance, given how noisy automotive voltage is, but even then there’s a risk that a large voltage spike will kill it (I’ve heard of 30V+, but I don’t know how true that is). Perhaps there’s some way to set up a filter before the driver that could shield it from all that noise?
Well I was thinking would it be possible to rig say 20 XM-L emitters in parallel direct to the 12v via some nice wiring and someway to suppress the voltage down to say 3v.
If your looking at keeping it 3a or below, search for a kis module and run a driver that can handle 5v off that. Or really any buck module with a wide input range with a set output for what ever driver you want to use
The kis module has something like a 5-24v input 5v output stock. And they can be had for cheap
Nevermind my above comment. Don’t think it will be economical with 20 emitters
Although they can be had under a buck a piece when buying bulk. Think I got mine for about .50 each
Have you seen the discussion in my thread here? Lots of recommendations on voltage and/or current regulators too. The KD driver I bought is rated 3v - 18v input, single mode, cheap, and E1320 says it drives an XM-L at about 2A.
-Garry
If you are only going to used the lights when the car is running, I would run 5 parallel banks of 4S XML’s. That way the consumed voltage would be similar to the supply voltage.
Since car systems generally go 16v and higher when running, you need a resister or driver. I’d use this super cheap and simple diy driver for several off-road headlights and it works good. I use a different regulator though, the LM1084IT-ADJ (can handle 5 amps). You would need one regulator for each band of 4S xml’s. You need a small heatsink for the regulators. The regulators consume 1.25 volts. So, 4 typical leds and the regulator would consume 13.25v. The regulator would burn up the rest of the excess supply voltage.
Taskled has purpose built drivers for auto voltage but mainly lower current (<1A).
Any vehicle produced in the last decade will run at 13.8-14.6 volts while the engine is running, and this voltage is determined by the voltage regulator in the alternator. While a vehicle is running, the vehicle battery (12 volt battery) basically is acting as a voltage “buffer” to smooth out the voltage “spikes” (these spikes are usually quite small). If a vehicle’s ECU were to see something like 16 volts the entire ECU and pretty much all of the electronics would “fry”.
While the vehicle is running, you can pretty much count on 14 volts as the supply voltage.
Keep in mind, if you’re talking about something like 20 XML’s, you’ll want to look into how much overhead your alternator has in terms of how many more amps it is possible to produce while still supplying the vehicle with all the electronics it is using.
Your right that most cars will be around 14+ volts when running, but I wouldn’t count on it. I would heat sink the regulators for 16v to be safe.
As far as frying electronics. I’ve had several friends drop in 16v batteries in their cars when drag racing. They would take off the alternator belt. One friend put in a 19v alternator so he would always have a 16v battery in place. They didn’t have any probs. They all said their cars ran better.
They are happy, that’s all what matters.
Taking the belt off leaves more power for wheels. A 19V alternator defeats the idea.
Most of the electronics probably get stabilized voltage anyway.