This is my first time using the device and so far I don't see any problems. I like the fact that it automatically detects the battery it's connected to. I have a fairly new car/battery (1 year old) so it shows full battery capacity. I'll leave it plugged in all day and see what happens. I look forward to using the device when I travel abroad and trying it out on my old car air conditioning/charging batteries. that the cable connectors have to be longer so that the bonnet can be closed from the outside with a block and strong clips. For now I give 4 stars because it works as described.