That vid is a fairly good tip and I didn't know about the light either. However, I gotta say that it's much better to keep a log of your batteries. When I'm out flying my H I always take a note of the power level at the point of landing when the battery is still under load and write it down in a notebook for later updateing of my battery logs when I get home.
To date, though, I've never reinserted a partially discharged battery in my H for a flight (I have done but only for bench testing and calibration purposes). In my book, if a battery is not full, then it is empty and ready for charging regardless of whether it has only been used for a few minutes, and I only recharge the number of batteries (minimum two) that I think I will use for a flight no earlier than the day before an intended flight.
For example, I have a job on for tomorrow taking some video and still pictures of a derelict farm house on the side of a hill. I expect to get the job done on just one battery so I've just finished charging up two and if, as I expect, I don't use the second battery on the job, I'll use it up on a recreational flight after the job flight to ensure that I'm not left storing a fully charged battery.