Have kept a bunch of old trucks for the past 30 years - sometimes as many as 20 ranging from pickups through fire engine and Mack LTL - and most of them are driven only by me, so they mostly sit.
Almost all use lead/acid batteries and most of those last 12 or 13 years if kept fully charged. Have had success with the Battery Minder (have added wiring to trickle 4 batts per unit) and the cheap units from Harbor Freight have been very dependable - one unit per batt.
I have downsized a bit with the fleet.
