In System Information there is line with battery status. New Lithium batteries are 100%. New Alkaline are over 90%.
Out of curiosity, I put the weak batteries back in (measured at 1.28V) and used that remote to check the battery status. System information "RF remote battery status" reported 40%. I also noticed that the remote worked OK if the backlight was OFF. As soon as the backlight activated, the yellow LED dimmed a bit and the RF link stopped responding. Yup, these cells have VERY high internal resistance if they can't even power the LED backlight
I tried to see if the battery percentage was updated each time the remote transmitted and it apparently is not. It acts like it updates when you first enter the help menu..... I put good batteries in while still in the system information menu, backed out of system information and went back in and it still showed 40%. It only updated to 80% after I backed all the way out to My Shows and went back into system information.
I have seen the battery status as low as 20% with the remote still working fine so the battery status represents voltage at an undetermined load and is therefore not a final determination if you have high internal resistance NiMh like I did. These cells were probably 8 years old and since they charged, retained their charge and were not used in high current devices, I was unaware that they had gone high resistance.
The batteries in my case were NiMh but the same thing can happen to alkaline cells, especially offbrand ones. They may provide adequate voltage unloaded but sag to the point where things stop working when loaded.
Paul