As per datasheet for Relay (Panasonic: JS-M Series); all nominal values are mentioned for coil current, voltage & power dissipation. Based on these values how to estimate maximum values for current, voltage & power dissipation for relays.
e.g.
Nominal Voltage: 12VDC
Nominal Operating Current: 53.3mA
Nominal Operating Power: 640mW
This relays is designed for 12V system; (Automotive Domain); Can it be used for 24V systems?
I have checked this relay on 31.5V power supply. It was working fine without any damage. So I am not sure whether to use same 12V relay for 24V system or not.
Best Answer
You should not do this. Assuming 150°C insulation the temperature rise at 85°C ambient is 65°C with 16V applied. Refer to figure 3 on the datasheet.
Even if your ambient temperature never exceeds 25°C (so the allowable temperature rise would be 60°C more), the maximum allowable voltage would be
Vmax = 16V\$\cdot \sqrt{\frac{125°C}{65°C}}\$ = 22VDC (Ta \$\le\$25°C).
The assumption in the above is that temperature rise is proportional to coil dissipation.
Use the proper voltage relay or add a ~1W resistor in series with the coil.
Note that the resistance of the coil varies significantly from room temperature to the maximum coil temperature, however at the maximum it is roughly the same, whether you get there from high ambient temperature or from heating due to over-voltage.