Canon Sx160 is battery info.
My SX150 and SX40 both will show full charge for the longest time while, for hundreds of shots. Then when they show less than full charge, I have only twenty or thirty shots left before the battery is exhausted.
There are battery technologies that are used in DSLRs that show a gradual decline in battery capacity so you know where you are. But I am guessing those battery technologies cost significantly more so they are not seen in lower priced cameras.