I have a 2 year old P3Standard and should like to test the low battery failsafe, and the 'lost contact with controller' failsafe.
To test the drone battery, I presume I just keep flying it (over a field of grass!) until low aircraft battery takes over, and keep my fingers crossed.
Is it safe to just switch off the controller (simulate controller battery fail), to test that drone will RTH safely??
I'm a novice pilot, flying for fun, so any tips on the safest way to do this without risking my aircraft?
Thanks.

Yes, if you turn off the controller the drone will go into RTH mode as long as the homepoint was recorded before you took off.

Failsafe RTH will be triggered if the remote controller signal is lost for more than three seconds, therefore, turning off the remote controller is okay to conduct the failsafe RTH function of your drone. However, there will be Failsafe safety notices that you may refer to the image below. Hope that his information would satisfy your query and may you please always have a safe flight.

You can simulate a low and critical low voltage of the battery via setting menu. If you fully charged battery then set the low to 90% and critical to 85% and take off,and have a look what happens.
Do not forget to reset the values to the default or your own setting.

Peterx Posted at 5-6 02:17
You can simulate a low and critical low voltage of the battery via setting menu. If you fully charged battery then set the low to 90% and critical to 85% and take off,and have a look what happens.
Do not forget to reset the values to the default or your own setting.

I would caution people from setting the critical low voltage too high. When the battery level reaches critical, it will land wherever it is at and you will have minimum to no altitude control.

It should not made by a normal misson,it should be a test flight and inbound of a diameter of 50 meters and not 2-3 kilometers. Simply a test of functions of an intelligent flight battery.
My settings for a misson is 30% low and 20% critical tprevent a deep discharge of the cells. Thanks for your comment and tip with the altitude control.
My test was successful.