This makes me think of the Sofirn C8F. It’s about the same size and I think the output level and hotspot size will be about the same. Have you considered that light?
I agree, I think the C8F with dedomed XPLs would have similar performance. I did buy the host but have not built it yet since I’m still deciding on the emitters. I have a few lights in this size and output range so I’m trying to think of how to make it a bit different.
But I think the D1S is a special host. It’s very light and compact especially for its reflector size. For a short time I had my 3x3 array of XD16s in the light and and I liked it, but the XD16 array is not reliable yet. So a sliced XHPx0.2 is the next best thing.
I currently have a C8 with a XHP50.2 and a RMM FET with 2 18350’s in it. What do you suppose one of these new boost drivers would do to the output of a XHP50.2 when changing over from 18350’s to a single, high drain 18650 (30Q/VCT5) and one of these drivers?
(Obviously these aren’t out yet, so no one knows exact specs. It’s all conjecture at this point)
I did a similar C8 mod a couple months ago. I ordered the parts from Mtn of course, and I asked Richard if I should wait for his boost driver instead (he teased these on his Instagram page last year). He said the 2x18350 with fet would definitely be brighter, since the boost driver will only put out about 3.5 amps at 6 volts, which will be 8-10 amps pulled from the 18650 as the voltage sags.
But as you said, let’s wait and see. At the very least, you’ll get much longer run times, right?
The 18650 will have more capacity and lower internal resistance.
You just need to replace the springs or bypass them to get the full potential out of the C8. Boost drivers request can pull even higher currents than a FET driver by upping the voltage.
Lowering the resistance at any point in the flashlight itself is crucial.
My thoughts: a quality 18650 would have so much less resistance than 2 18350’s that a FET wouldn’t be pulling nearly as much as a high boost driver. I guess it all depends on what the amps are set at on the boost driver, right?
In a single cell light, a boost driver will pull more current as the voltage drops farther and farther from the emitter’s foward voltage to keep it in regulation.
That means using steel springs not bypassed at say 6A current, the voltage drop will be around 0,3V. Which is huge.
Say the output power is 18W for a 6V emitter
Our cell at varying voltages and current draw:
18W= 4,20V x 4,28A
18W = 3,9V x 4,50A
18W = 3,60V x 5,00A
As you can see, current draw increases as voltage decreases.
Now, let’s introduce a steel spring(–0,3V for every voltage)
18W = 3,9V x 4,62A
18W = 3,6V x 5,00A
18W = 3,3V x 5,45A
That means you have to pull even more current out of the cell.
Imagine that but at 50W power! You would be pulling at least 12A at 4,2V, and that could go up to 14A at 3,6V, or even 15A at 3,3V! With only a steel spring and no bypass, that would be go much worse. And that is not even counting the internal resistance of the cell, and other resistance in the circuit.
You’d probably get either a low voltage warning almost instantly due to the huge spring resistance, a burned spring, or a huge power loss.
That problem is still there with a FET driver, but since current pulled goes down with voltage, it isn’t as much trouble.
TLDR: For such a powerful boost driver, going with a single 18650 is crucial for both energy and power density. You also need to get rid of all almost all contact resistance, which includes the springs.
Edit: Remove something I should not have said :person_facepalming:
Well I guess I jinxed myself. I was using the above C8 tonight, since we were talking about it… all of a sudden it decided it only wants to use moonlight mode for all levels of intensity. Low is like 1 lumen, medium 10 lumens, high 50 lumens.
Looking at the led on low, one of the arrays is brighter than the other 3. Did I finally blow the emitter?
This boost driver (input voltage is lower than output voltage) can drive 6V LEDs, such as the XHP50.2/70.2 from a single rechargeable lithium-ion battery at an output current of up to 4.2A. It can also drive a 12V LED, such as the XHP35, at up to around 1.3A. The MTN-BST2 uses a highly efficient synchronous boost converter squeezed into a tiny 17mm form factor.
Unlike most of the high power boost drivers out there, this driver can achieve a wide dimming range and utilize popular firmwares.
This driver takes up to 10 business days to be built, tested, and shipped. Your order will not ship until the driver is completed.
Battery & Host Requirements:
In stock form, this driver will pull just over 10A peak current, therefore a 10A+ continuous rated battery is required (unless you reduce the input current limit). The more voltage the battery can hold under load, the better the driver will perform. Your switch, springs, etc. must be able to handle the 10A+ input current; this means that you must have high performance or bypassed springs in your light.
The driver _must_ be soldered into the pill or held firmly in place with a retaining ring. This is required both for adequate thermal and electrical performance. If during use the light turns off and on, the driver is overheating and needs to be switched to a lower mode or turned off and allowed to cool. Continued operation at excessively high temperature will damage the driver (damage from excessive temperature will not be covered under warranty).
Specifications:
Boost Converter (input voltage must be lower than output voltage)
3V - 5.5V input voltage range (suitable for a single lithium-ion battery)
Designed to drive 6V LEDs, such as the XHP50.2 and XHP70.2 at drive currents up to 4.5A
Can also drive 12V LEDs, such as the XHP35 at currents up to around 1.3A
Output voltage range: ~6V —- ~13.8V
Output current range: 6V LED: 1A —- 4.2A
XHP50 / 50.2
XHP70 / 70.2
MT-G2 6V
12V LED: ~1.3A
XHP35 HD / HI
Input Current Limit Option:
If you are running any battery that is not capable of 10A+ continuous discharge current, you must change the input current limit to a lower value.
~10.5A | 4.2A w/ 6V LED maximum recommended output current
~8A | 3.5A w/ 6V LED maximum recommended output currnet
~4A | 2A w/ 6V LED maximum recommended output current
Output Current Option:
The output current is set using one or two sense resistors. You can choose between any of the following output current limit options:
1A
2A
2.5A
3A
3.5A
4.2A
Firmware Options:
Currently only guppy3drv is available. We will have Bistro available as soon as we get it 100% dialed in.