2010 S 550 Battery
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Junior Member
Joined: Nov 2010
Posts: 25
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From: Texas
2010 S 550
2010 S 550 Battery
We left on a trip and the car was in the garage for about 30 days without starting. We returned home and it started just fine. The next day, the battery was dead. Had to jump-start it. The battery level was down to like 3V. Performed a tickle charge overnight at 2 AMPS? Next day started fine. A few days later nada on the start, recharged again. Note battery was at 12.8 v after re-charge. I disconnected the battery terminals and left overnight. Reattached the next day and car started fine. With car running, v=14.x, so the alternator appears good. Car is now sitting with the battery terminals connected and V-12.5V. Will check again tomorrow to see if there is a parasitic draw somewhere.
If there is a parasitic draw,. any suggestions? I have tried to make sure any thing that could draw extraneously is unplugged, radio in off position etc. How hard is it to track a parasitic draw? Please note, the 2010 S550 only has a main battery under the hood, not in the trunk. There is an auxiliary battery located behind the steering wheel area. Note car has 164K miles.
If there is a parasitic draw,. any suggestions? I have tried to make sure any thing that could draw extraneously is unplugged, radio in off position etc. How hard is it to track a parasitic draw? Please note, the 2010 S550 only has a main battery under the hood, not in the trunk. There is an auxiliary battery located behind the steering wheel area. Note car has 164K miles.
Last edited by bohaiboy; Jul 28, 2025 at 09:28 PM. Reason: Typo
MBWorld Fanatic!
Joined: Oct 2019
Posts: 5,238
Likes: 1,803
From: Colorado
G550
I'd have the battery load tested at an auto store. Batteries can begin dying at any time (my OE battery died at 42 months). A bad cell can drain the battery just as a parasitic load would do.
Super Member
Joined: Jun 2025
Posts: 794
Likes: 254
From: USA
To find a parasitic draw, wait 20+ mins for the car to sleep, then check the current with a multimeter should be under 50mA. Pull fuses one by one if the draw drops, that circuit is the issue. Common culprits: glovebox light, faulty modules, or the aux battery. If unsure, a shop can help.
