Thanks guys for clarifying things. I was in Wal-mart today and saw they had a Black and Decker charger for only $26. I may go back and purchase it.

If I have this straight, so long as the charger is either plugged in and used every few days, or even if it's not, so long as the car is started and run every few days, there is no chance of the charger doing any harm to the battery or anything else even without installing a diode. Do I have it right?

And it's fine to leave it plugged in not only overnight but even for a couple of days?

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Pictures of the MB: http://s230.photobucket.com/albums/ee41/EricandRobyn/1981%20Mercedes/

1981 300 SD with a Goldenrod water block and Injetor line heaters. EGR is missing

1999 F-350 with HP X-over, Dahl 100 Fuel Filter, Coolant by-pass filter, CCV mod, Tymar intake.

Both on single tank WVO blend