In the mean time, could you not set FS_ACTION to 0: Nothing ?
Thank you so much @lordneeko. I have figured out this issue.
The parameter fs_action is set to 0:nothing, the rover runs on auto mode without transmitter.
@rmackay9 very appreciated. I have figured out the battery fail trigger.
Set it in full parameters list. Set batt_fs_******, when the low battery voltage is triggered. But the tip is measure the actual voltage should at the point of you want to trigger. Then calculate the Voltage Divider (calced).
E.g. Measured battery voltage is 11.00V, old Voltage Divided is 10,
your actual battery is measured as 12V
You get new Voltage Divided is 10x12/11=10.909
Then you put 10.909 in Voltage Divided (calced).
The 12V is you want to triggered value.
I am not sure is correct way or not, but it works for me now. I will keep testing it.
Thanks guys for all of your help.