Added the Schumacher SE-1-12S-CA charger to our 01 F250 diesel to maintain its 2 batteries. Not a daily driver and truck sets between use and or isn't driven long enough to really charge batteries. Over 2 weeks and truck lucky to start, voltage below 12.1 and it's not without jumping. Other than not good for batteries to drop and set that low for frequent long periods  -dragging out the charger just inconvenient. Standing voltage after a few days generally was about 12.2v and continue to drop. Decided to address.