[W126 Coupe] Update on Battery Drain

[Dick Spellman]

Hi Vance:

Why not put a trickle charger on the battery when it's parked at your 
home.  That'll at least keep the battery up for now.

One question, is the brand and same size of battery in your SEC 
available from a local retail shop?  I ask because while it sounds like 
you are doing a rapid current drain on the battery using a conventional 
tester, there is also a new means of actually measuring the condition of 
the lead plates.  In order to do the test accurately you need one NEW 
battery to take a reading on and note it followed by taking the same 
reading from your SEC battery.  There is a formula (I have it) that will 
tell you if that battery has a problem that the current drain test will 
not reflect.  Anyway, let me know how old the SEC battery is and if it's 
still available on store shelves by the same brand and size.  I have a 
MOS tester that I can send to you to run the prescribed test which will 
conclusively rule out the SEC battery's condition.

Regards,

Dick

Vance Rowley wrote:

>Hi Guys,
>
>
>  I am almost at a loss on this one. I contacted my local Meta dealer and spoke at length with him regarding the possibility of my alarm/immobilizer being the problem. Basically the answer is 99.9% chance it isn't. I also looked on some forums and found the backup battery is built into the alarm sounding unit. I have already run a test with this disconnected, but this intermittent current draw was still there, so there goes the theory of the backup battery taking the current.
>
>I have tried replacing all the fuses that are "hot at all times" with 1amp fuses. Left them in overnight, but all were still OK next day, but the current draw had obviously happened overnight as the engine only just turned over. I even went to my local car accessory place and did another drop test on the battery, hoping that although my last tests showed the battery was OK, that maybe I was mistaken somehow. It tested perfectly and yes it's charging perfectly too.
>
>It looks like something that must be connected on "the other side of the fuses" that must be taking this intermittent current draw, comming directly from the battery. The factory alarm is disconnected completely. This was done when the Meta system was fitted and this problem, although has being going on for years, it hasn't always been there. I have had the car parked up (shortly after I bought it) for two weeks with the alarm armed and when I returned and started it, it was as if it started on a brand new battery.
>
>I have even completely had the after market stereo system disconnected in case for some reason this might take an intermittent current draw. No luck there either. The normal current draw at the battery terminal is at between 85ma and 90ma with the alarm / immobilizer armed and everything connected. But something is taking this intermittent 6amps or so now and then. I even stood watching the meter (connected between the battery and terminal) for nearly an hour today, but didn't even see this once within this time period. In the past I have seen it, but it's so intermittent, you have got to be very lucky to be in the position to measure and see it. Even then, because it's not there all the time, what chance is there of finding out what it is?
>
>As you know from previous posts, I have ruled out the vacuum pump that feeds the central locking system and all of the normal checks have been made, but there is nothing in the archives (at least not until now) on an intermittent problem like this one. I am basically out of ideas. Am I the only one with a 560SEC that this has happened to? I welcome any ideas and I am at a stage where I would not consider any idea a stupid one. The only idea I have myself is to just drive it every day, which is what I used to do, so that idea is ruled out at the moment. And yes, the other idea is to disconnect the battery when not in use. This I was doing, but by ideas and suggestions, I mean to find the problem, not just cure the symptoms.
>
>Completely mystified.
>Vance
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