I have a small powerbox, only about 17ah with a 150watt inverter. I want to keep it topped off since I won't use it very often so I want to trickle charge it while not in use. I have a 1.8 watt panel as well as both a 2.2 watt and a 5.5 watt model. However, when I plug any of them in and there it a little light, although, it says that it is being charged, the powerbox makes a slight, squeaking sound, sort of like the warning sound it makes when there is too big of a load being used on it. If, however, it is in full light, ot none at all, there is no sound and it seems to be charging just fine. I tried hooking up a 15 watt panel and it seemed to work just fine in any light. So, does anyone think that there is there something wrong with the powerbox?