camping lantern

On basically every camping trip in the last couple of years, my only source of light was the LED of my smartphone. It's pretty dim, doesn't attach to the tent's ceiling and in general isn't an optimal solution.

Since I have all the necessary electronics parts by hand, I once again made an attempt in creating stuff from scratch which eventually turns out to be much worse than off-the-shelve stuff.

Here's the list of requirements:

• compact - check
• bright enough - check
• >4h battery life - failed
• weather proof - failed
• accessible parts - check
• fancy switch - check
• …that prevents unintentional operation - failed
• cool design - kind of check
• even lighting - check
• USB charging port - failed

Not a full success admittently… still rather useful.

BOM:

• 186050 battery UPS PCB. The UPS is not ideal but since I initially wanted to add a 2nd USB port for charging while lighting and charging the light, this made sense to me. The low battery life eventually made me refrain from that additional goal.

https://aliexpi.com/CRjn

• 18650 Li-ion battery. The unrealistic capacity rating, a price of ~2€/pc and that ballsy decision to name a Li-ion battery something with “fire” in it got me curious (spoiler: they didn't fire yet). I even measured their capacity and obviously the manufacturer faked the rating roughly by the factor of >10!

https://aliexpi.com/wA67

• LEDS. I opted for warm white LEDs here. They're totally fine and come with an adhesive tape attached.

https://aliexpi.com/omCk

• Switch. For my rotary switch I used a microswitch which I initially acquired for a 3d printer.

https://aliexpi.com/IR2i

• 5x M3 x 6 plastite screws. Metric might work too but won't last as long.
• Some insulated wire.

Total cost incl. shipping is roughly 12€ in parts. You could already get a pre-build solar lantern with 2x 18650 for that price: https://aliexpi.com/EM4v

…just sayin. These are not affiliate links BTW.

Battery life:

I already mentioned the bad battery, but real life battery life …life is even worse than calculated.

Given the 9900mAh battery can only deliver 1000mAh (which it doesn't, but it's close), the battery is supposed to provide 3,7Wh. Since the PCB involves a power converter which I pessimistically estimate at 80% efficiency, we can decrease the real energy to ~3Wh.

One LED consumes 12mA of current at 5V, which makes 1,8W for 30 LEDs.

So in theory - even with that lame battery - the lantern is supposed to provide ~1,5h of uninterrupted brightness. In reality it's something close to 1h unfortunately. And then it goes into on/off mode for another hour. So better use less LEDs (24 would still be more than bright enough) and a decent battery of something like 3000mAh.

Assembly:

There's some soldering involved unfortunately and it's a bit tricky to fiddle the cables through all the openings. Connect the switch to the UPS-enable jumper and the LEDs to the 5V output of the UPS. If some details in wiring are unclear, don't hesitate to ask me in the comments.

Then attach the cut LED-strips to the convex sides with the adhesive tape. This seems to hold up well enough. Make sure the UPS is not enabled when fiddling the wires to the LEDs since a short could destroy your battery or PCB.

Connect the LED strips in series and make sure to attach the topside wires last. Route the cables to prevent the top cover from cutting into the insulation.

Then add the lampshade, the top cover, ring, bottom cover and hope you never have to disassemble it again. Assembly of this thing is absolutely terrible.

Printing:

These are rather uncomplicated prints. Use supports where necessary (should be obvious on where to place it) and print the lampshade in vase mode and some transparent/translucent material. I used filament from recycled plastic bottles for all the parts and it appears to be the perfect material for that gadget. Transparent/translucent material is also recommended for the inner part, so the PCBs LED shine through, which let's you see whether the battery is full or still charging.