Buenos días. Hoy enseñaré a cómo quitar la protección de sobrecalentamiento en la linterna Convoy M3.
Empezamos quitando la batería y desmontando el driver del cuerpo de la linterna
Aquí vemos más de cerca la resistencia NTC
Resistencia medida a unos 21ºC - 23ºC en la habitación
La calentamos un poco para confirmar que es la resistencia NTC, con un secador de pelo a 45ºC - 55ºC
Como vemos la resistencia disminuye
Procedemos a desoldar la resistencia NTC con un soldador de punta fina aplicando un poco de flux en los contactos para facilitar la extracción
Más de cerca, los pines no se tienen que tocar al ser una resistencia NTC.
Haré la prueba con una batería Liitokala 26650 5000mAh (5.3mAh medidos desde 4.2V hasta 3V)
Montada la batería
Éxito, lleva más de 10 min en modo TURBO
IMPORTANTE, no mantener el modo TURBO mucho tiempo ya que acorta la vida útil del driver y del LED. Yo utilizo el modo TURBO solamente cuando voy en bicicleta ya que el viento disipa el calor de la linterna
I don’t want to totally disable the temperature protection on my M3 but would love to increase the threshold a lot (by maybe 30 degrees at the driver). Can anyone suggest what resistor I would need to replace the existing one with? Or could I maybe solder a standard resistor in parallel with the NTC resistor to increase the overall resistance?
That’s a NTC Thermistors being used it’s resistance decreases as heat increases. So instead of parallel you would need to add a standard resistor in series. After that it’s beyond my skills. You could experiment with limiting its heat. Desolder the NTC place a thin layer of some thing under it and then resolder it. The gap off of the board with only the solder points as your thermal path may keep it a touch cooler.
Thanks texas shooter, I was wondering if “series” was actually the correct answer… I will look to see if there is a NTC thermistor with a different scale, so that the resistance doesn’t drop so low when it heats up. Or an insulator made with a few layers of Kapton tape may do the trick as well, like you mention.
I will also buy some thermal pads from ebay to increase heat transfer from the driver to the flashlight body, like someone else has already done here on BLF.
I am also thinking - if I fit the thermal pads I may just be able to delete the NTC thermistor without worry because my Efest 26650s probably won’t be able to maintain the voltage needed for turbo even for the 10 mins the OP reports anyway!
Sound like your on the right path. I was thinking of a couple of thin toothpicks under the NTC then pulled out after soldering. Put a real gap there. I’ve tried thermal pads, little improvement. Thermal epoxy gave better results. It increased the thermal mass and allowed the heat to conduct out from components. Then thermal pads to move it from the thermal epoxy to the head. Good Luck.
Good feedback on the thermal pads, thank you. Yes I can see how basically “potting” the driver in thermal epoxy would be great for heat transfer and something I had thought about as well. Thanks for all the ideas, you have given me a lot to think about. Appreciate it!