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DaveTheCarGuy, Car Enthusiast
Category: Car
Satisfied Customers: 240
Experience:  AAS in Automotive Technology.
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E550: e550why does my battery die for no apparent reason?

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e550 why does my battery die for no apparent reason? What is draining the battery even though the engine is off and no lights are on?

Hi there - the big question is how long does it take the battery to die?


Most batteries will self-discharge (just sitting) within about 3 months.


Even though your car is sitting with the engine off, and all the lights off, there is a small amount of current flowing to the on board computers, navigation system, alarm system, etc. This is called parasitic draw, and typically the higher-end the car, the greater the parasitic draw.


How long does it take for the battery to go dead?

Customer: replied 2 years ago.
The battery drains at times in less than an hour after I turn the car off.
This does not happen always. But I am never sure what will happen. It is not due to a bad battery, nor to a long period of no use. Something else is draining the battery even though the car is off.

Sometimes this can be caused by a loose battery connection. Verify that the connections are tight. You E550's battery should be in the trunk. Also, I know you say it isn't the battery, but how do you know? With the high demand, and high drain on the battery I've seen several E550's eat a battery in 2 years or less. Also sometimes you have a battery with a bad cell, and it can go bad at any time.

The only other thing that can drain the battery that fast without causing damage to the rest of the car would be the alternator. It takes a lot of current to drain a modern battery in less than an hour, and only the battery itself, the alternator, and the starter have that strong of a connection that wouldn't blow a fuse.

Customer: replied 2 years ago.
Had Mercedes Benz roadside assistance come to jump start the car. Tested battery. Not the problem. Recommended I take the car to the dealership . He couldn't figure out why.
I'm confused why you rated my service poor. You gave very little information and I gave you options. The roadside guy couldn't tell you what's wrong with the vehicle, so how do you know that he is right when he says the battery isn't the issue? If you would like to run some tests on the vehicle I'll gladly help and coach you through, I apologize if my previous answer was not the one you were looking for.

DaveTheCarGuy, Car Enthusiast
Category: Car
Satisfied Customers: 240
Experience: AAS in Automotive Technology.
DaveTheCarGuy and 5 other Car Specialists are ready to help you
Customer: replied 2 years ago.
He tested the battery. And determined it did not need replacing. If you needed more information to be able to make a determination, then you could have asked for that info more specifically. Alternatively, you could have said you could not make the determination given the info you had. As it is, the answers you gave were too general to be helpful. It is the kind of info someone like me would already know before approaching a professional for help.

I appreciate, however, your willingness to coach me through a testing process. Perhaps, that should have been part of your original response. What are those tests?
I agree with you and apologize. I am still new to this online troubleshooting, so I still have some bugs to work out. Leta try and rule out some variables, please answer these questions:

Does it happen more frequently in specific weather, rain, cold, warm?

Does it make a difference how long you drove the car prior to it sitting?

Any recent maintenance?

Any modifications to the vehicle?

Any issues when the car is running, dim lights, poor performance, ect.

Does your car have the optional air suspension? If so do you have any lights on for the system?

Have you tried anything since first asking the question?

Can you recall what the service person tested (other than battery) when he came out and gave you a jump start.

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