Mike, Stay away from any device that is described as a "battery charger." Instead, simply connect a small regulated power supply directly across the battery terminals, and adjust the output voltage to "float" the battery at its resting voltage. The power supply voltage needs to be just high enough to offset the tendency to self-discharge, and to supply the few milliamps drawn by the electric clock and possibly a keyless entry or alarm system. This float voltage will vary between vehicles, depending upon the age and type of battery, the ambient temperature, as well as the amount of "vampire" current drawn by accessories that are always in standby mode. The cigarette lighter receptacle often cannot be used to connect a battery float power supply, because it usually is connected to the battery only when the ignition switch is on.
73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Mike Morris WA6ILQ Sent: Friday, May 22, 2009 1:32 PM To: [email protected] Subject: [Repeater-Builder] OT - recommendation needed - battery charger Got a friend who is laid up with back problems. His car has been sitting for several months between uses. He has already lost one battery from sitting idle. He wants to purchase something packaged like a trickle charger that can be connected to the battery and left there (maybe even semi-permanently with a cord hanging out the grille). Does anyone have a suggestion for such a product ? Maybe one of the "desulfator" devices ? Mike WA6ILQ
