I am designing a Li-ion battery discharger. So the discharged power, gets dissipated as heat. Although I have a heatsink and fan, I cannot make the fan work with full speed because it makes so much noise. Inside the software I have a PID which controls the temperature of device. It gets the temperature data from one of the temperature sensors located on the PCB, somewhere near to heatsink but not touching it. So the temperature I measure is less than the real heatsink temperature. I have set the threshold of the PID to 65 Celsius. That makes temperature to oscillate between 63 Celsius and 70 Celsius. So my question is, are the standard electronic components withstand that much temperature for 7-8 hours? Would it effect the component life drastically? As components I have some power resistors, MCU, ceramic capacitors, resistors, diodes etc. I know there is no specific answer for this question, I just want to get some general opinion about it. Thank you beforehand.

P.S: English is not my native language, if there are some parts that needs to be fixed, please feel free to do so. Edit: There is 7-8 Celsius difference between the hottest component and the measured temperature value.

  • \$\begingroup\$ First rule for closed loop controls is to have your measurement point as close as possible to what you want controlled. Second rule, which sometimes trumps the first rule, is to have as short of a time-constant between measurement and control output as possible. Third rule is to make that time-constant ACTUALLY constant and not allow it to be variable about some supposed average time constant. That said, I gather all you want to know is if you are seeing 70 C "somewhere near" some other place, can whatever is at that place you don't measure take the unknown heat there? I've no idea. \$\endgroup\$
    – jonk
    Feb 18, 2020 at 7:33
  • \$\begingroup\$ Thank you. I added some parts to question. \$\endgroup\$ Feb 18, 2020 at 7:40
  • \$\begingroup\$ Also see here for something possibly related. \$\endgroup\$
    – jonk
    Feb 18, 2020 at 7:41

1 Answer 1


Depends on your end application and life time requirment.

We do testing at elevated temperatures around the temperature you have quoted for just few months to assure about the life time of the product. It means, we are already stressing the product and the components.

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Depending on the expected life time of the product you can plan. See the operating temperature of all th devices on board, especially the displays and capacitors.

  1. For example, a super capacitor at that temperature range won't even hold half the charge it would at room temperature, at a slightly higher temperature, it will fail permanently.
  2. The rating of the devices come down with higher temperature. Power rating for resistors, capacitance for capacitor for example.
  3. The diodes will have derated forward current and elevated reverse leakage currents

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