My '01 E320 4Matic is about to sit in the garage for 3 weeks. In past events a couple of years go, (sitting for 2 weeks), I returned to a dead battery. I do have a old Montgomery Ward 4amp trickle charger, but am not comfortable using it for that length of time. Is the corse of least resistance to disconnect the battery? TIA

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....just drive'em!
'89 300TE White w/Blue, 152K SOLD!
'93 300E Blue w/Tan, 154K SOLD!
'01 E-320 4-Matic wagon, 130K
'67 Vette Conv. White w/Blue, 217,421K

Did you remove the key from the ignition? Later Benz (including my wife's 2004 E320) WILL flat the battery unless key is unplugged. Should restart after 3 weeks if you do. Hers does.

Disconnecting battery may cause you to reset everything.

The answer is a battery tender, not a trickle charger. A trickle charger will just charge and charge regardless but a battery tender only delivers as much charge as necessary and then shuts off. I have 5 cars, a pickup, and a tractor, including 2 classics that sit for 7 months out of the year and a couple of German cars with lots of electronics that love to draw down the power while the car sits. I keep battery tenders on most of them. Thanks to the battery tender, my oldest battery (in a '74 Porsche) is 13 years old and still going strong.

https://www.harborfreight.com/12-volt-deluxe-battery-maintainer-and-float-charger-62813.html

If your battery goes flat in 3 weeks, you need to find out why. See if you have a light staying on or something somewhere that's pulling power. On a modern vehicle with computers and other gizmos that always suck power you should be able to get a couple months of sitting before even worrying about the battery charge state. Older cars without any ECU's or parasitic draws could go for several months.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Keys are never left in car/ignition. Sitting in totally dark garage, no lights are ever left on. If there is a hidden draw, it will have to be discovered at a later date. So, I'm disconnecting the battery. I really don't have anything to loose. Thanks guys!

__________________
....just drive'em!
'89 300TE White w/Blue, 152K SOLD!
'93 300E Blue w/Tan, 154K SOLD!
'01 E-320 4-Matic wagon, 130K
'67 Vette Conv. White w/Blue, 217,421K

Occasionally I plug my tapering charger into a simple mechanical timer so that
the charger isn't always on. It wasn't the table light version but the more
robust, outdoor timer which I think was in the 15-20 amp range.

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-- raymond~
47º 34'N 122º 18'W