last week, we did a fun experiment on flashlight batteries! actually, i picked up a science fair book and this ideas was in it. we gathered several different D batteries and stuffed them in flashlights... turned them on and monitored them! we had energizer, duracell, dollar general and another-which i can't recall. duracell won! it lasted over 28 hours! if you don't want to invest in different batteries.... maybe you could ask the grandparents or supportive neighbors or friends?