The 4138 manages to combine most of the features of a conventional charger with elements of a trickle unit. It picked our battery up from 1.2V, charging at 4.5A and switching to maintenance mode at an indicated 13.5V. The winner of our previous test, it stood up well, but it doesn't come with a direct battery connection lead and plug, and when compared to the rest of the group, it is veryheavy and bulky.