I have two of them. There have been a number of good reviews on the BT. Sulphating is what eventually kills a battery and the tender is designed to maintain a charge the charge. Some trickle chargers have auto shut offs but that is not the same thing. They allow the battery to discharge to a certain point, which permits a certain amount of sulphating, before they turn back on. A friend sells them at his shop and I asked whether I should use the junior or the standard. He told me that with the junior you can't charge a low battery, or it takes a long time. The standard will bring a flat battery up to full charge.