[R129 SL] battery issues

[Peter S]

Hi Markus and William,

The first thing I do (and have just done this to may 129) is to check the 
battery.  My old battery used to go 'flat' quite quickly (was 6 years old), 
so I purchased a new one.  The new battery was supposably tested and charged 
and I dropped the battery into the car....but... went flat in 4 days.  I 
checked the battery and whoa.... 0.4 volts across the battery terminals. 
Technically the battery should be 'stuffed' at this voltage.  As the new 
maintenance free batteries are mostly Calcium Silver Lead Acid types, the 
old style charger will not charge these batteries.

I have a 3 stage ramp charger for Calcium batts, but did not move from 0.4 
volts, so the battery supplier used a 17 amp charger - still would not move. 
So we used an 80 amp (8 stage ramp charger)charger, and that moved it 
reasonably quickly.  Remember the battery at this stage was less than a week 
old (it also has a 36 month guarantee).

The battery supplier indicated I have a problem in the car so check out the 
car.  I indicated that I start the process at the beginning, and after 
putting a supplementary battery in, the drain was only about 0.2 amps from 
the clock etc, so it was unlikely to be the car.

I was concerned the new battery could be faulty (or fail early) but after 2 
months, all is still going well.  So in this case, the battery was at fault. 
To check currents, I use a DC clip on ammeter (Fluke 41B).  I have a low 
current probe so it is easy to check 'standing' load currents without 
removing battery leads etc, and as Markus has indicated, if the current flow 
is too high, start pulling the fuses so you can track the cause.

Good Luck with finding the fault.  Here in Palmerston North, New Zealand, it 
is 10 am, light breeze, 23 degrees C, sunny and I am just about to do my 
day's work in the SL.  I usually travel with the top down, so time to enjoy 
this nice weather.

Regards, Peter S.

----- Original Message ----- 
From: "Markus Meyer" <markusfmeyer at hotmail.com>
To: <r129list at mbcoupes.com>
Sent: Tuesday, January 06, 2009 5:09 AM
Subject: Re: [R129 SL] battery issues



>

> There are a few ways to check it out.  One is to pull a fuse each night 

> and see if the drain stops, then you have located the circuit its on. 

> Another way involves needing a test light, and disconnecting one of the 

> battery cables (I forget which one right now).  You connect the test light 

> between the cable you disconnected and that battery terminal, then pull 

> fuse by fuse (individually) until the light goes out, then you found the 

> source of your drain.  Of course if that fuse has several items on it, you 

> still need to investigate further, but at least you've narrowed it down.

>

> Markus

>

> ----------------------------------------

>> Date: Mon, 5 Jan 2009 10:57:02 -0500

>> From: jennianenterprises at verizon.net

>> To: r129list at mbcoupes.com

>> Subject: [R129 SL] battery issues

>>

>> 1995 sl500

>> replaced the battery and it goes totally dead

>> if the car is not started for about 4 or 5 days

>> any ideas on what could be drawing power

>> and killing the battery - thanks

>> bill

>> The MB Coupes Website!

>> R129 SL Mailing List

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