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

So it will feature 300lm?
Seems a bit low i believe.

I got the 3W from DBSAR’s discussion with sac02:

But even with 2A a really lightweight build is sufficient.

Three 7135’s provide more than enough light for this type of application. My similar in concept 4th annual contest entry, the mug-o-light, has three and I never run it on high. I understand why DBSAR reduced it to 2.

I think we talk 700-1000mA (3 * 7135 max)

The integrated shelf of the Q8 is not needed, a small flat area above the tripod mount for the USB connectors (well that is going with my idea of using the tripod mount to secure a rubber flap to ensure water proofing which seems logical to me)

Above that the diffuser and wires holding poles
So I expect the lantern to be lighter but some weight helps inbsturdy placement so is not bad.

Unfortunately, weight=good at BLF, while when I go out camping reducing weight is all-dominating!!! If I want a firm base I rather make the base wider instead of the light heavier.

Well true, but I don’t see a lot of fat on Q8 tube, tail and lower part head so removing the integrated shelf that is not needed and a good diffusing downwards facing led part seems the lightest 4 18650 config without going titanium
Seeing the HJK thermal images if powerbanks makes me think the few fins remaining on the head do have a function.

We are talking 172gr of cells

Plastic lanterns are plenty but come on, it only needs one time placing the backpack down wrong to render them useless.

I would be interested in this lantern. Thanks.

Djozz, just see how much metal is ditched looking at the Q8 an a rough sketch

The Prototype is based from a SRK body, but with the top of the flashlight sawed off, so its not as long as what a diffuser attachment would be on a Q8. (Also the lantern prototype is a “down-firing” LED set up, and is far more efficient, better light angle, and has far less eye glare than an up-firing lantern/flashlight-Diffuser has, ( especially when the lantern is on a table or carried by the top lanyard. USB-C port interface is not a good idea as its not the standard cord interface that comes with 98% of phones, tablets, portable 2-way radios, etc. The charge-out port would need to be the standard USB-A type plug. USB 3.1 format is irrelevant for a charge-only port, as there is no data transfer, only 5 volts DC power for charging. (its the came across USB 1. 1.1, 2.0 , 3.0, etc.)
As mentioned above XP-L & XM-L emitters seem to be in the most efficient amps-vs-lumens-output in the 700mA to 1000mA range. (1050mA (or three 7135 chips) produces around 460 ~ 500 lumens, plenty for lantern use. The prototype uses 2-7135s, ( 700mA ) ans produces average 300 ~ 350 lumens, and with the current down-firing XP-L 7A3 LED it seems close to a 40 watt incan bulb for output, and its still far brighter than any other factory bought LED lantern i have/tested.

Nice example drawing :slight_smile: as you mentioned, the lantern would be shorter than a Q8/SRK with a diffuser head, as 25 % of it is removed for the lantern design. (seen below)

DBSAR, I hope this isn’t viewed as argumentative or a belabored point, but how are you estimating those output numbers? They seem high to me. I know it doesn’t matter in the grand scheme, but I like to have compulsively need as much accuracy as possible in all things I care about, lol.

I’m looking at Cree datasheet for XP-L V2 (based on availability of 7xx tints in V2 bin) at 1050mA and 25*C, is 446Lm. At Tj=85*C (this light won’t get that hot) it is 400Lm. I think it is safe to say somewhere between 400 and 446 emitter lumens at 1.05A So I think actual OTF output will be substantially less with not only a lens, but a diffuser included as well.

Looking at the Relative Luminous Flux vs Current chart, at 700ma my best estimate of the output would be 69.2% of rated lumens, so somewhere between 277 and 309lm (again, at the emitter).

djozz test graphs are similarly hard to read perfectly accurately (tabular data would be a nice bonus for future tests), and djozz is quick to point out his tests are not calibrated to any standard output. But his tests show about 310Lm at 700mA and 480Lm at 1A, for a higher binned V6 XP-L.

I think that diffuser eats more lumens than one might expect. I wouldn’t be surprised if OTF lumens were down by 30% from the emitter output?

I am so happy that this project got some traction. I have an off grid hut…and some solar panels. I know you all will like this flashlight when all electricy is off and the zombies are chasing you….

Thank me later when the zombies are here.

I used a Lux sphere to test various LEDs and driver set ups when i built it. From my tests then to your claims above my measurements are quite accurate. I posted above: ” 1000mA range. (1050mA (or three 7135 chips) produces around 460 ~ 500 lumens” were not talking single-lumen accuracy here, just averaged tests. I did my tests in the sphere with the bare LED, not a diffuser. This lantern prototype don’t really have a diffuser, just a clear main globe and a lightly frosted inner globe. Not a completely opaque diffuser as in many lanterns sense.

I used my solar 40-watt folding panel to power BT-C3100 charger to charge 18650s each day this past summer on my trip to the wilderness. It is possible with a built in charger for the lanterns cells, & using a 20-watt or higher panel?USB charger, it is possible to sustain this lantern indefinitely with charges to power it for several hours every night.

Update: currently testing to shoe-horn in a TP4056 based charger module in the lantern prototype, to see if indefinite sustainability is possible with running the lantern on high every night for 4 hours, then charging the next day using a Poweradd 40-watt folding solar panel multi-charger with a 2 amp USB charge output)

This sounds really promising. I’m not normally a built-in charging sorta guy, but I can see the benefit here. I don’t ever go off the grid, but dang if I don’t dream about it sometimes. Maybe one day… :smiley:

If this all works out I’d like a link to that solar panel please.

I asked this before but it was at a time when this thread wasn’t getting much attention: could a lantern like this be a good application for a light pipe? “Candy cane” shaped pipes would make it possible to mount the LEDs in an area with more thermal mass while still emitting downward, right? My understanding of light pipes is that they work on the same principle as TIR optics, but I’d be the first to admit I don’t know much more about TIR than you’d learn in a basic physics class.

Im interested… :slight_smile:

The charger panel i have is the Poweradd SP20140W i bought from Amazon last year: https://www.ipoweradd.com/products/poweradd-40w-usb-port-dc-output-foldable-solar-battery-charger

I have used this solar charger with great results. It has charged (and even sustained running power while running) my small ASUS netbook, and charged a phone at the same time while in remote wilderness areas. I also built a custom adjustable voltage regulator box to use with it, and it powers my Opus BT-C3100 charger with no issues. There are many good solar chargers out there, ust make sure you do your research and read customer feedback on them.
I do have several different solar chargers and portable off-grid power systems, The photo below shows 6 of them. (the Poweradd 40-watt is the one on the blue chair to the right.)

I’m still very interested.