*BLF LT1 Lantern Project) (updated Nov,17,2020)

I’m quite bothered by the unilateral “updates” by Sofirn considering this was a community light. Altering the flashing pads in that manner is just a dick move, but changing the default 7135 configuration from 3x7135 to 7x3135 while removing the ability to alter it is quite significant and DBSAR should have been consulted.

Ahh, but we had some fun, and knew it wouldn’t last forever. Canny Chinese eh? :face_with_monocle:

As far as i know our development team was unaware that modification was done or discussed before hand.

How long does a development team have any control over what a manufacturer decides to do with a project?

So …… has the name changed to Sofrin LT-1 :person_facepalming: :beer: :beer:

Only change I’ve noticed is that the new one is described with a Q8, whereas the old one does not have that descriptor. That may be how they are going to morph the name over time. As far as the unit, looks identical to the original. Will know more when it is delivered.

I asked Barry about the relocation of the flashing pads on the new driver. He said he did not know. Maybe it was an engineer‘s decision to align the circuitry on the business side of the driver as efficiently as possible? I keep asking them to provide us a flashing adapter but I do not expect this to happen anytime soon, especially without a standard pin layout.

I was told the new version will have all 7135 chips enabled for maximum brightness. There is no thermal regulation in LT1 but I do not expect this to become a problem as long as ambient temperatures are in a reasonable area. Maybe the top of the lantern will become a bit warmer than usual.

For the duration defined in the contract.

I don’t think there is any real recourse here. We have to hope that Sofirn understands why aspects of the light were designed the way they are and keeps them that way.

It’s great to see an update from you…and the possibility of other interesting variants!

But most importantly, I hope things are genuinely settling down for you finally.

New to BLF, flashlights and lanterns. I thought I ordered the newest powerbank version from the sofirn website. Did I end up with the right thing?

What the… Another version?! What are they doing?! At least it makes more sense than the previous version.

What in the world? There will soon be more LT1 variations than FW3A variations.

We had the original, the one that supports type C-C, the new one with screwed up pads and powerbank out, and now this one with pads but without the POT.

I’ve also seen this one which implemented a red channel but was never made, I assume due to them lacking the code

Unfortunately this is most likely an in-house (á’la Sofirn) variant of the classic version (i.e. no powerbank feature).
The only other place I’ve seen this design is an Aliexpress feedback entry from a Moldovan guy here from 05 Jul 2021 12:17.
And as you can see from both the product description and price of that Aliexpress listing, it is pretty clear that it is referring to the classic version.

I have the power-bank-equipped variant and its driver looks like the one in the orange lantern here.
Of course, in theory, yours could be just another layout design around the same components, but it is unlikely, as the bottom layer of your driver PCB is rather suspiciously missing the very distinctive, rectangular grid-pattern of the thermal vias of the thermal pad of the powerbank controller IC. (The central, copper-colored rectangle with holes in the new, PB-equipped driver). Which indicates yours does not have such an IC. (Or if it does, they completely screwed up its thermal design :slight_smile: )

If you want to approach the question from a more practical angle, I can recommend three things:

  • If you have batteries and a Type-C to Type-C cable and a suitable USB device to be charged, then just plug them together and see what happens :slight_smile:
  • If you don’t have all of the above, only the batteries and A-to-C cable, then start charging the lantern, and watch the indicator LEDs. The TP5100 charger IC of the old design lights up the charging LED constantly. On the other hand, the IP5310 power-bank controller blinks it at 0.5Hz. I am intentionally not writing about LED colors, because there is no way for me to know what color LEDs Sofirn was using for what purpose in your case. Long story short: if your charging LED blinks, you probably have the PB feature, if it is constantly lit, you probably don’t.
  • Unscrew the driver, take some pictures of its top side with all components markings visible, and send it here. If you do that, I’ll be able to tell you if you have the BP feature or not with absolute certainty. Hope it helps!

Thanks for the feedback, Lux.
FWIW, in my opinion, the whole programming-pad-layout thing is being blown way out of proportion… I mean come on guys, if anyone is nerdy enough (like me, for instance) to want to reflash the FW of a lighting apparatus, and know how to flash MCU FW in general, I think it’s safe to assume they also know their way around bench tools, soldering equipment, etc. and they can make their own programming fixture, or temporarily just jerry-rig the wires directly to the pads or the MCU pins. It’s an inconvenience, sure. But it is hardly the end of the world…

Yes, that was my greatest concern as well with the new model. (Whether the not too over-engineered thermal design of the LT1 can handle the extra dissipation by the additional 2x2 7135s…)
But I made some calculations, then performed some torture-tests yesterday which made me a bit more relaxed:

The top “cap” of the light has a surface area of 5850 mm2, which as a rule of thumb, should translate to a thermal resistance (Rth) in the neighborhood of 7 °C/W.
Rth (junction to solder point) of the LH351Ds 2.2 °C/W according to the datasheet.
Rth of a typical MCPCB is around 1 °C/W.
Rth of a reasonably applied half-decent thermal paste could be estimated around 0.3 °C/W
I=2450mA at full blast, while Vf of the LEDs (in worst case, i.e. when either extreme of the tint range is set) is 2.8V. Considering an efficiency of 70% that gives a power dissipation of about 4.8W, total.

If you put all this data together, mix some thermal design theory in it, you will receive a predicted heatsink temp of 62.6°C and LED junction temp of 79,4°C at an ambient temperature of 29°C.

The measurements I’ve done afterwards, seem to confirm this theory (heatsink temp of 66.0°C, junction temp 82.8°C, in a non-ventilated area at 29°C ambient):

What I actually measured are the head/heatsink temps. (Simultaneously via non-contact thermometer, and K-type thermocouple, always taking into account the highest reading) The junction temps are just projected from the heatsink temps. There is no way to measure them directly. However if anyone wants to determine their values more accurately, they could measure the MCPCB temp instead of the heatsink and offset the measured values by 4.8W*2.2 °C/W= 10.56°C. This way you could eliminate the potential inaccuracies stemming from the estimated MCPCB and thermal paste Rths.

Now, 82.8°C might sound awful, but actually it is not. The “design temperature” of today’s power LEDs (LH351D included) is 85°C. This is where the manufacturers expect OEMs to run them in their end-devices. This is the temp they are binned at, this is also where their environmental stress tests are performed. It is a perfectly safe temp for our LEDs (the top end of their operating junction temp is 105°C!).

I also measured the temperature of the battery tube. Its 44°C is also not catastrophic, most Li-ion cells today allow a max discharge temp of 60°C. However I am sure it will have some lifetime penalties if the cells are subjected to it on a regular basis: Some researchers say every 10°C above room temp reduces the lifetime cycle rating by ~25%. I can neither confirm nor deny if this statement is accurate though… maybe someone with more practical experience with the quirks of Li-ion cells can.

Thank you, great analysis! Still, 70 °C is pretty hot when you touch it. :wink:

I know, I learned that the hard way :smiley:
Joke aside, even the 45C handle/tube temperature is not that pleasant on the long term. It’s not burning, but your palm will sweat like a pig, that’s pretty much guaranteed :smiley: So in a scenario when you intend to hold the lantern in your hands for prolonged periods, it might be good idea to step it down a bit.

Thanks for such a detailed reply! Still waiting on my C-A adapter but I found a USB C-C cable and connected it to an old BLF LT1. It powers it in headless mode and when the battery tube is screwed in, the new LT1 button color changes to blue-amber, I guess indicating charging? When the New LT1 is connected to a power source, the button does not blink. I also have the same new/short manual that was posted recently.

This is specifically the model I ordered:
https://sofirnlight.com/products/new-version-blf-lt1-lantern-with-anduril-20-power-bank-function
“Black-NewVersion-with-Battery: LT1 new version + 4x batteries (inserted) + USBA to USBC cable”

I can unscrew the driver if you want, but hesitated since I didn’t know how hard it would be to get back together :nerd_face:

I went ahead and did it. Sorry for the low quality, it was hard to keep it positioned correctly and snap the photo.

I’m more confused than ever about the LT1. Does this “Sofirn 1.0” version act as a power bank or not? Why are there only two bridges for the 7135 config?

It definitely has power output.