SL55/63/65/R230 AMG: HELP - trickle charger damaged alternator??
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Joined: May 2010
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From: Chicago
E63 SL55 996TT C5Z06
HELP - trickle charger damaged alternator??
Hello gang - am having a issue with m 2004 SL55 with 74k mile on it where the rear trunk consumer battery doesnt appear to be charging while driving the car as I'm getting 12.4 volts at start and it just declines to about 11.0 when I am forced to turn the car off and put it back into the garage and trickle charger.
I put the car into storage last month as I'm in the Midwest and dont drive it much in the winters so I keep it on a Noco 3500 trickle charger. Earlier this year I replaced the voltage regulator on the alternator (theres a DIY on doing this voltage regulator replace from under the car) and the car has been running perfect for months until now.
Only change I can identify is that the car was sitting idle for a month on a trickle charger and I am wondering if the trickle charger could have damaged the alternator or the alternator fuse thats located in the passenger side foot well????
Thanks in advance for any feedback or guidance as I was so happy to finally have the SL55 working again after the coil over conversion and am cringing at the idea of yet another isssue with the alternator and cant seem to keep this car on the road consistenly for more than 3-4 months before some issue comes up (
I put the car into storage last month as I'm in the Midwest and dont drive it much in the winters so I keep it on a Noco 3500 trickle charger. Earlier this year I replaced the voltage regulator on the alternator (theres a DIY on doing this voltage regulator replace from under the car) and the car has been running perfect for months until now.
Only change I can identify is that the car was sitting idle for a month on a trickle charger and I am wondering if the trickle charger could have damaged the alternator or the alternator fuse thats located in the passenger side foot well????
Thanks in advance for any feedback or guidance as I was so happy to finally have the SL55 working again after the coil over conversion and am cringing at the idea of yet another isssue with the alternator and cant seem to keep this car on the road consistenly for more than 3-4 months before some issue comes up (
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MBWorld Fanatic!
Joined: May 2010
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From: Chicago
E63 SL55 996TT C5Z06
@poppyboy thanks for the reply.
Battery is 1 year old (AGM, 760 cold cranking amps) but it was unfortunately fully drained one time last month but I was able to use my trickle charger to charged it and then use repair mode on the trickle charger to get it back to about 725 cold cranking amps. Am wondering if the battery is now bad and won’t hold a charge?
when the car is running the voltage directly from the rear battery using my battery voltage/load tester only shows 12V which leads me to believe the issue is with the alternator.
the car had been running perfect with a new voltage regulator installed earlier this year which is why I’m confused as to why now (after sitting on the trickle for a month) is the alternator not charging the battery.
Battery is 1 year old (AGM, 760 cold cranking amps) but it was unfortunately fully drained one time last month but I was able to use my trickle charger to charged it and then use repair mode on the trickle charger to get it back to about 725 cold cranking amps. Am wondering if the battery is now bad and won’t hold a charge?
when the car is running the voltage directly from the rear battery using my battery voltage/load tester only shows 12V which leads me to believe the issue is with the alternator.
the car had been running perfect with a new voltage regulator installed earlier this year which is why I’m confused as to why now (after sitting on the trickle for a month) is the alternator not charging the battery.
Senior Member
Joined: May 2019
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From: Lincolnshire, IL
2005 SL55 AMG
AGM batteries can be fickle. Generally, no batteries like to be fully discharged. It’s often difficult to get them back after that. You may need to jump on that warranty for a replacement and see if that solves your issue.
Thread Starter
MBWorld Fanatic!
Joined: May 2010
Posts: 1,227
Likes: 185
From: Chicago
E63 SL55 996TT C5Z06
good call I’m going to return the battery today and see if a new one corrects the issue. Thx again
Senior Member
Joined: Mar 2021
Posts: 273
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From: Rocky Mountains, Colorado
Just sold my '11 Porsche TurboS cab for an '03 SL55!
Make sure you trickle charger is AGM compatible. They require a unique charger that's different from the Lead/Acid types. One clue can be that the lead/acid chargers can overheat the AGM's and the sides of the battery will bulge out slightly.
