Anyone want to hazard a guess as to how long an E320 CDI with a good, fully-charged battery can sit during the summer months without the car being started? On other cars I've owned I would assume 3-4 weeks. But I understand the W211 presents a greater load when sitting.

Just planning for some travels and wondering what length of time would warrant disconnecting the battery cable.

Thanks.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Get a trickle charger or a solar battery maintaner if it's parked out in the street. When batteries run flat computer modules go bizerk on some of these cars.

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CENSORED due to not family friendly words

Won't really work with my set-up. Just trying to figure out how long they can sit. I definitely don't want the battery to drain all the way.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Assume you have a 120AH Ampere hour battery and the car draws 100ma when sitting ( it should be around that give or take. ). Then you have 1200 hours before the battery is flat. You probably can't start the car with battery at half flat but the electronic should be maintained for a long time, close to a thousand hours. Check the AH of your car battery.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

I replaced the fuel valve on my W210. This was during the saga with the bad crank sensor. The car had been sitting for over a month and had multiple starting attempts on the battery with no real opportunity to run. Battery is about 4 yrs old, genuine MB.

I had to crank I think 3 or 4 cycles to get the car to start. It started getting slower and slower. It finally caught and fired when the battery probably did not have enough to muster even one more revolution.

Just about every module had a fault code for low voltage.

I can only imagine what this would do to a W211 which is an order of magnitude more complex than a W210.

120 Ah is about right for these batteries. 100 mA, with 168 hr/week, that’s about 7 weeks to total discharge, assuming constant current as the voltage declines.

I’d go out and throw my Fluke 87 on my E320, but then I would have to go though and reset half the systems in the car since I have to break the negative lead for this test.

When I had my 124 wagon, I measured its standby drain for another thread, and it was like 15 mA. I literally could see the clock ticking every 20 seconds by the spike in current (up to 40-50 mA for less than a second). Most of the drain was due likely to the radio memory backup lead and the Chinese remote keyless box I added. And I did not have to do anything to the car other than reset the clock when I was done.

100 mA standby drain in a modern car is not out of the realm of possibility at all.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

It is really dangerous cranking a modern car with a weak battery. If the read / write process of a rolling code smart key is interrupted mid cycle, the system will brick.

I firmly believe that failures blamed on a faulty jump start are actually caused by cranking with a weak battery. The ML key seems to be a common victim.

Sterling Truck had a TSB where cranking with low voltage could lead to the electronic heater / ac control software locking up. The only way to fix was to replace the controls with an updated unit.

Find a way to make a charger work. There are far too many 10+ year old electronic components on that car each with it's own consumption rate to predict how long the battery will last. As previously mentioned, it's not just a simple matter if will it start or not after x weeks.

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CENSORED due to not family friendly words

Probably easier just to disconnect the battery cable. Then just a matter of resynching a few things.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

After I had issues with my battery draining last winter when the vehicle wasn't being used, I hooked up a wire lead to the battery in the trunk and now connect a CTEK charger of appropriate size to the connector. Take a look:

MB appproved battery charger/maintainer: CTEK

This will assure your vehicle has the proper voltage to start and run. It also will extend the life of your battery!

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-- Chris

'95 E300, 216k miles, Silver Surfer
'05 E320 CDI, 138k miles
'07 S550 4matic, 69k miles

Gone but not forgotten:

'76 300D, 350k miles?, SOLD in 1995
'75 240D, 300k miles, SOLD in 1991

Again, you're playing with 10+ year old computers where their internal memory power supply is questionable at best. You could reconnect the battery only to find one of the SAM modules, or EIS or TCU module had its memory wiped or corrupted. The problem is common throughout this era MBs.
https://youtu.be/8snjCbo8exg

Also if you do decide to disconnect the battery, remember this car had 2 batteries.

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CENSORED due to not family friendly words

I was thinking the same thing. However, I am not sure how the aux battery plays into the system. I do know that on my parts car ('03 E320), the main battery was totally dead. I could not get into the trunk to fix it because the previous owner hacked up the key cylinder. I installed a fully charged aux battery, and it did nothing to get the trunk open. The car had no response from any electrical device whatsoever. I then powered up the fuse for the trunk latch, and opened it with the switch on the door. Could the aux battery just be there to maintain the memory for all the modules?

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All Diesel Fleet
1985 R107 300SLD TURBODIESEL
2005 E320 CDI (daily)

LOTS of parts for sale!


EGR block kit
http://www.peachparts.com/shopforum/diesel-discussion/355250-sale-egr-delete-block-off-plate-kit.html

1985 CA emissions 617 owners- You Need This!
Sanden style A/C Compressor Mounting Kit for your 616/ 617 For Sale + Install Inst.

Sanden Instalation Guide (post 11):
http://www.peachparts.com/shopforum/diesel-discussion/367883-sanden-retrofit-installation-guide.html

The aux battery is there as a backup for the SBC brakes in case the main battery fails. Given the opportunity the car will drain both batteries.

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CENSORED due to not family friendly words

Agree....that is why I am going to make sure the battery is kept charged.

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-- Chris

'95 E300, 216k miles, Silver Surfer
'05 E320 CDI, 138k miles
'07 S550 4matic, 69k miles

Gone but not forgotten:

'76 300D, 350k miles?, SOLD in 1995
'75 240D, 300k miles, SOLD in 1991

That's interesting...thanks. Yeah, seems like keeping the battery charged is my best bet.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I'd also dig around for a dealer prep or service manual. The Chrysler PT Cruiser has a fuse that gets pulled to reduce loads during storage / shipping. I'd be pretty confidant MB has such a fuse / switch / connector.