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SL550, GL550 & E350(wagon)
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66 Posts
Discussion Starter · #1 ·
Hi All,

Does the second battery get any charging when the car is running?

I routinely hook up my trickle charger (1.25 amp) and it soaks for two or three days to bring the second battery to "full charge". I thought it was because my SL was a victim of short trips. But.......I just returned from 500 mile Interstae trip and same deal...took a two day trickle soak.

If this is normal...fine. If not, perhaps it's a cuurent drain.

Comments please.

Thx, Don
 

· Registered
2013 SL550, 2003 SL500
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4 Posts
Hi Don,
I've had the same experience. What you refer to as the second battery (in trunk) is actually the main vehicle battery. I'm sure that it gets charged (I've measured the voltage) when the engine is running.
Don't know why it still takes a charge after a long run. I did read somewhere that there are vehicle systems that are constantly drawing current, even with everything off and locked. Perhaps that is the cause.
Take care,
Bill
 

· Registered
2000 BMW M5, 1997 F250, 1998 Altima, 2005 Honda Repsol 1000RR, 22FT Bayliner Capri Bowrider 5.0L
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106 Posts
the venicle is very smart, it only uses the starter battery for starting, and only charges the starter battery when it needs to. dont be alarmed.. just drive and be happy! :)
 

· Undercover Moderator
2002 SL BRABUS 5.8 Silver Arrow; 1992 SL BRABUS B11; 1996 S Class diplomat ride
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5,507 Posts
Hi All,

Does the second battery get any charging when the car is running?


Comments please.

Thx, Don
Yes, just like the R230 SL....:thumbsup:
 

· Registered
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75 Posts
Second battery

Found the main battery in the trunk but I'm told by the Dealer that the smaller battery, which needs occasional charging, is somewhere under the passengers seat. I can't find it! I'm told that should it have to be replaced the car has to go to the Dealer where it takes about 2 hours to swap the old for the new. At $125/hour plus the cost of a new Mercedes battery that should come to about $500

Does anyone know where to get a look at a shop manual?
 
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