SL/R230: Battery discharge graph and data
Thread Starter
Senior Member
Joined: Nov 2021
Posts: 471
Likes: 119
From: North West England
SL500
Battery discharge graph and data
If anyone is interested, I just used a data logger to record the battery drain on my car after turning it off and locking it.
I have just found a 200mA drain on the battery (added ancillary device) so was interested to see what drain remained.
excel spreadsheet covering about 1 hour at 1 second intervals enclosed
I still have about 90mA drain, so still something draining battery
Most interesting thing is it took 15 minutes for the car to fully shut down to give the lowest drain reading on the battery.
I have just found a 200mA drain on the battery (added ancillary device) so was interested to see what drain remained.
excel spreadsheet covering about 1 hour at 1 second intervals enclosed
I still have about 90mA drain, so still something draining battery
Most interesting thing is it took 15 minutes for the car to fully shut down to give the lowest drain reading on the battery.
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GLE 580
If anyone is interested, I just used a data logger to record the battery drain on my car after turning it off and locking it.
I have just found a 200mA drain on the battery (added ancillary device) so was interested to see what drain remained.
excel spreadsheet covering about 1 hour at 1 second intervals enclosed
I still have about 90mA drain, so still something draining battery
Most interesting thing is it took 15 minutes for the car to fully shut down to give the lowest drain reading on the battery.
I have just found a 200mA drain on the battery (added ancillary device) so was interested to see what drain remained.
excel spreadsheet covering about 1 hour at 1 second intervals enclosed
I still have about 90mA drain, so still something draining battery
Most interesting thing is it took 15 minutes for the car to fully shut down to give the lowest drain reading on the battery.
Thread Starter
Senior Member
Joined: Nov 2021
Posts: 471
Likes: 119
From: North West England
SL500
No the multi-meter is battery operated, so only connected by 50MegOhm input.
Will be putting it in line with SAMs next to track down the drain, but 3 x better than before...
Super Member
Joined: Aug 2017
Posts: 520
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From: Scottsdale AZ
2015 SL550 & 2012 S550 4matic
Very interesting posts and thanks for sharing g0rsk. Could the 90ma be associated with alarm system? Always on when locked. Might be 1st place to check, even if it’s just part of the 90ma drain.
Super Member
Joined: Sep 2018
Posts: 746
Likes: 185
From: Melbourne, Australia
2005 SL 500 R230
Always interesting, seeing discussions around battery issues are a perennial certainty. There is a long thread somewhere about what the 'correct' quiescent drain should be. Under 50 mA was the consensus,
Thread Starter
Senior Member
Joined: Nov 2021
Posts: 471
Likes: 119
From: North West England
SL500
It is possible. I did use one of these to find my 200mA drain
However resolution is only 10mA so using it to track down the last few 10'smA would be difficult.
When checking the alarm module fuse, a few minits after locking the current went from about 50mA to 0mA
I may go through the pre-fuse box to try and find where the final draw is coming from, just to see how low I can get the parasitic drain, but I suspect 80-90mA may be the best I can do. It will make life much easier for my battery maintainer.
Next weekend I will repeat my measurements, but without locking the car, to see how deep, and how fast the car goes to sleep (electrically).
However my CLK goes for its annual roadworthy test next Saturday, so may be pre-occupied with that...
Member
Joined: Apr 2014
Posts: 89
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GLC, EQE SUV
I followed the steps by letting the battery drop to 10%, letting it sit for about 10 hours, and then charging it to 80%. The range now shows 295 to 311 miles at 80%, which is an improvement compared to a year ago.
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Junior Member
Joined: Jan 2024
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From: Wiltshire, England
2000 R170 SLK 320 manual, 2018 E200 E Class Estate, 2016 GLA 250, 1996 R129 320, 2003 R230 500.
I have a 2003 R230 500 with a really irritating parasitic drain which I have yet to track down. The problem has been exacerbated by a CTEK charger which hid the drain.
I found a fault in the glove box light which I have fixed (it now goes off with the cover shut), checked the boot light which was working properly, and found an ancient Nokia mobile which was on charge permanently - phone removed but not the cradle yet so that's next as is looking at the fuses and relays with a thermal imager. I can leave the car unlocked which eliminates the alarm as a cause.
Loads of people here in the UK seem to have the same problem but wildly differing causes!
I found a fault in the glove box light which I have fixed (it now goes off with the cover shut), checked the boot light which was working properly, and found an ancient Nokia mobile which was on charge permanently - phone removed but not the cradle yet so that's next as is looking at the fuses and relays with a thermal imager. I can leave the car unlocked which eliminates the alarm as a cause.
Loads of people here in the UK seem to have the same problem but wildly differing causes!
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Thread Starter
Senior Member
Joined: Nov 2021
Posts: 471
Likes: 119
From: North West England
SL500
Leaving the car unlocked will not help your parasitic drain, as it will prevent all modules from fully shutting down, which can take 15 to 20 mins after locking.
The alarm module has a rechargeable battery inside that is always on charge. If this battery goes faulty you will have a permanent drain.
Removing fuses one by one is very entertaining way to pass some time, but will also not necessarily highlight a fault, as modules depends on other modules, and a lot of components are not directly protected by a fuse.
Have you measured the drain with an amp meter?
The alarm module has a rechargeable battery inside that is always on charge. If this battery goes faulty you will have a permanent drain.
Removing fuses one by one is very entertaining way to pass some time, but will also not necessarily highlight a fault, as modules depends on other modules, and a lot of components are not directly protected by a fuse.
Have you measured the drain with an amp meter?
