Why is it, that when a electronic devise that uses a battery, detects that the battery is running out… that a light comes on??? wouldn’t the light take up extra battery from what little battery is left??
austin
Also, when your phone reads “battery low” it means “battery dead”.
Probably for the same reason that the army labeled the bottom of cans “Open other end” rather label the top “Open Here” 
Arjuna34
That’s how it works. It drains the battery so it’s never wrong. 
Well, which would you rather have – a device that kept running until it died with no warning, or one that had the decency to inform you of its impending demise? If some devices had absolutely no low-voltage shutdown, it’s conceivable they could become permananently ruined when the battery runs low.
Contrary to what Poirot says, ‘battery low’ really means ‘battery low’. When the ‘low battery’ light comes on, it indicates “I have enough power to run this light, but not enough (or almost not enough) to keep operating otherwise”. The term ‘dead battery’ is just a way of saying that the battery is too low to work with that device.
Now if the light that it turned on were a 10-Watt halogen lamp that projected “low battery” on the clouds, that might be a little excessive.
the anthropomorphizing panama jack
But damn cool, you gotta admit.
I have thought about this and have come to this conculsion: I would rather have a device that runns without consumming extra power during most of it’s run time and use a little extra to warn me that it’s out and needs replacement batts. then a device that uses extra power just to let me know that the batts are ok then save the power when low.
Lets say you can run this thing 5 h on batts. would you rather runn the battery ok light for 4.5 hours and save power for .5, or get slightly longer run time by not lighting any light till you need it and get maybe 5 h w/o the light and 15 minutes with?