kolvatten lights

I got 2 of the kolvatten motion activated bar lights to put under my kitchen cabinets. they worked OK for about 3 weeks but now both of them are dead. when I change the batteries they work for a couple minutes and then die again. has anyone had this problem with the battery lights? the other thing I was thinking is I somehow have an entire pack of batteries that suck, because every time I've changed them they've been from the same pack of Sam's club batteries.