Battery exchanged completed and all codes preserved! I bought an Interstate MTP-93 battery--most powerful I could find. At Home Depot I bought 8 feet each of red and black #10 THHN wire and two sets of battery alligator clips. At Radio Shack I bought an in-line 50 amp rated #10 wire blade fuse holder (#270-1234) and soldered it in line on the red wire. I installed a 15 amp fuse (only trying to protect against an accidental short of the hot lead during the battery exchange). I hooked up to the donor battery as described above by Ozzy and retained power during the exhange, very carefully keeping the red lead protected to avoid a short. All was normal when done. Great procedure!

Appreciate the advice--

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Jim Herold--Current: 1987 190E 16V, 1999 ML 430--Past: 1971 280 SL, 1972 250