relay holding current

[LaserTazerPhaser]

Datasheet does not depict any holding current. Whats the rule of thumb for these category of relays?

http://www.hongfa.com:8080/pdfjs/web/viewer.html?file=/Uploads/PDF/HF102F_en.pdf&stamp=1559602009559

[KMoffett]

Take a voltage a little higher than the "drop out voltage" and divide it by the coil resistance.
Ken

[rfengg]

Assuming that you are reducing the current to save on power, ~30% of the nominal operating current should be fine to "hold" the armature of the relay.
30% reduction in the coil current, should give you ~1/10 power savings.
The only downside to this is you cannot operate reliably in this condition if you are in a harsh environment with a lot of vibration and shock to the relay.
Is the relay driven by a DC voltage or is there an option of PWM-ing it?
The currents can be deduced from the voltages on the data sheet divided by the coil resistance.

[LaserTazerPhaser]

Assuming that you are reducing the current to save on power, ~30% of the nominal operating current should be fine to "hold" the armature of the relay.
30% reduction in the coil current, should give you ~1/10 power savings.
The only downside to this is you cannot operate reliably in this condition if you are in a harsh environment with a lot of vibration and shock to the relay.
Is the relay driven by a DC voltage or is there an option of PWM-ing it?
The currents can be deduced from the voltages on the data sheet divided by the coil resistance.

Going with this 40amp relay http://www.hongfa.com:8080/pdfjs/web/viewer.html?file=/Uploads/PDF/HF165FD-G_en.pdf&stamp=1559625739820 instead as it handles more current. Its going to be powered by either a wall adapter or 12v battery pack series with a SPST series to relay coil since high current SPST switches are far more costly. Its going to switch a 18.5amp adapter into an inductive load

[KMoffett]

This might help: http://www.learningelectronics.net/circuits/reducing-relay-power-consumption.html
You would need to adjust voltages and component values for your project.
OR
https://www.instructables.com/id/Relays-DC-999-Less-Power-Latching-Option/

Ken