Assistance Required for 2018 S320 Battery Issues

[Mistral]

S320, 2018, 32,000 kilometres

I would greatly appreciate any assistance or advice, as I am at my wit's end.


In recent months, I have encountered recurrent battery depletion when the automobile is not operated for a few days. Completely unresponsive, and on one occasion, it entirely reset the SRS system, resulting in a persistent error message necessitating a reset.

I am driving significantly less than I previously did for different reasons; at times, I may not drive for several days and then only for approximately 30 minutes.

During the last servicing three months ago, I had the battery replaced, since the technician indicated it was the 'large battery' and the cost was £250, which I accepted.

Within a week, the issue reemerged, with the vehicle struggling to start—repeatedly cranking, electrical systems malfunctioning, and ultimately 'catching' at the last moment. It operates adequately until the subsequent occasion.

Consulted a reputable auto electrician regarding the vehicle; his recommendation was to 'increase its usage.'

I left the car unused for seven days lately; it started successfully the first time but failed to start the following morning.

I have acquired a Ring Ultraboost 1500 Jump Starter, which functions exceptionally well and has successfully started the car four times when required.

The battery was depleted after being left for 24 hours with a Mercedes-Benz dealer for air conditioning maintenance.

I remained in the vehicle for 50 minutes utilising the Comand system with the engine off, received a warning to activate the engine, and, naturally, it failed to start.

I receive notifications from the Mercedes Me app indicating that "the charge level of your vehicle's starter battery is critical" and "12V battery is very low."

Therefore...

1. Is there an additional battery that requires replacement? My internet enquiries have yielded inconclusive results.

2. Can anyone provide any insights? I am quite exasperated; I cherish my automobile yet am losing confidence in it, which is somewhat frustrating.


Any ideas or suggestions would be much appreciated.

[Geek2232]

Upon deactivating the vehicle, certain systems stay operational for a duration. This is typical; but, at times, systems may fail to enter sleep mode, resulting in a parasitic current drain.

Did your esteemed auto electrician assess the current draw with the vehicle powered off?

[jimmy47785]

Possibly first equipped with a Tracker, which has a small rechargeable battery that is charged by the vehicle's battery. This diminutive battery may be defective; a similar issue occurred with a friend of mine. It took four months before someone made a diagnosis.

[Mistral]

Thank you both. I am uncertain whether any drain was pursued or really identified.


I cannot visit Mercedes-Benz dealers as they are untrustworthy individuals whom I cannot believe under any circumstances; they may convey anything to me, and fact have done so previously.

Is there a second battery available?

[clk320x4]

I am uncertain whether a second battery exists, unless it pertains to a hybrid model. Nonetheless, it is essential to consult an auto electrician or an independent Mercedes-Benz technician to identify any parasitic drain and attempt to isolate the module or circuit responsible for the issue.

Please inform us of your current town or city, and members will likely be able to recommend someone. 👍

[ML350_Colin]

Indeed, your vehicle will be equipped with an additional battery. If it is level, it may lead to many complications.

[BenTrevor]

A QR code sticker will be located on the passenger side B pillar. Utilise a QR code reader on your mobile device to reveal the location of the batteries within the vehicle.
I recently acquired a replacement auxiliary battery for my E350 from Tayna Batteries for £50.99, including postage, which arrived the following day.
Simple to execute, if you own a little spanner; no need to incur garage expenses.

In 2022, I acquired a replacement main battery from them: the F21 Varta Start-Stop Plus AGM Car Battery, 12V 80Ah, for £144.96 delivered.

[cumblechook22]

The original poster replaced the primary battery three months ago. It continues to discharge, necessitating an investigation into the cause.

[AMG33D]

The drain rate appears sufficiently elevated to indicate a defective alternator diode pack or alternator regulator. I experienced a comparable rate of discharge and anticipated discovering defective diodes. Following a considerable effort to remove the alternator, I delivered it for refurbishment, where it was confirmed that the diodes tested well. I requested that they replace the regulator while it was in their possession, and to my astonishment, this resolved the drainage issue.

I recommend seeing a vehicle electrician to assess your alternator. If you can access the alternator conveniently and own a digital multimeter, you can conduct the test independently

[AMG33D]

 

[Mistral]

Thank you - I will ascertain information regarding this matter.

[Mistral]

😍