YF-SF solar lamp
Teardown of few similar broken solar lamps. Specification:
- 4 LED panels
- 1 solar cell panel
- Li-Ion battery
- PIR motion detector
- pushbutton switching modes
Easy to open.
Solar panels are sometimes poorly glued, but corrosion does not seem to be a major issue (maybe they are just dying too early).
First PCB variant. 8-pin unmarked chip (microcontroller?), single transistor, PIR sensor on the back and pushbutton.
There is either 18650 or 14500 cell inside, it seems random.
Second PCB variant - that's why I'm naming these lamps as YF-SF.
One of the LED panels.
18650 cell with soldered wire. This cap is broken/unsealed.
Blown out 14500 cell.
... and another one.
The only one cell with any kind of markings - PCTXSQ IMR 14500 320 mAh (extremely low capacity), I guess manufactured in November 2024, so pretty fresh (this teardown is from September 2025).
These cell explosions typically are not too powerful, but here it broke plastic cell holder.
What's wrong with these?
- severely overcharging: from my tests open circuit voltage on battery contacts can reach 4.8 - 5.15 V depending on specimen
- slightly overdischarging: it is not turning off until cell voltage reaches 2.5V (maybe PIR sensor saves it most of the times)
- likely operating in very wide temperature range and overheating in the summer
They seem dangerous. Perhaps adding PCM board could save it.
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