Problem with R230 trickle charging

[clk320x4]

I own a 2007 Sl350, which I acquired as a temporary automobile. It is not often used, similar to many other SLs. Previously, I used a Noco Genus 10 charger to maintain the charge of the front battery, and it functioned well. Nevertheless, I had to address a little issue of corrosion in the trunk, so I removed the auxiliary battery and performed the necessary maintenance. After reinserting everything, I connected charger terminals to the auxiliary battery and saw a really peculiar activity.

The automobile undergoes a trickle charging process for a few days, but then experiences either a battery short circuit or a complete depletion of the battery. The remote becomes unresponsive, necessitating the physical use of the vehicle key to unlock it. Upon starting the automobile, all components come to life in a lively manner. The battery charger seems to indicate a momentary pause. No, I am not entirely flat. In fact, I have a green coloration. Can you observe? It then resumes regular behaviour till it begins the narrative over.

When I start the vehicle, I see the typical error message indicating that the auxiliary battery is dead. However, after driving for a distance of at least 20 miles and properly recharging the batteries, all of them indicate a voltage of 12 volts or more, and everything returns to normal.

Has anybody seen something analogous? I would like to mention that I own a S Coupe and I share the charger with it. The charger works well in that vehicle.

[Darrellll]

Based on my assessment, it seems that your battery is no longer functioning properly.

[bvlenci]

Utterly ordinary.

This topic has been extensively debated on this platform. If an R230 is not used for a month, there is a little but continuous loss of power, known as phantom drain. In this case, the Auxiliary battery will be depleted first in order to save the starting battery. By driving the vehicle for around ten miles, the Auxiliary battery will regain functionality, allowing you to operate the hood, air conditioning, and other components.

The next step is to thoroughly recondition and recharge your auxiliary battery in order to determine whether it can be completely charged once again. If the condition is too poor, it may need a replacement auxiliary battery.

However, if you, like the majority of SL users, are not using the SL for an extended period of time, it is necessary to consistently charge or trickle the auxiliary battery.

[clk320x4]

Thank you everyone. I want to attempt the removal of the battery and then charge it while it is not connected to the automobile. If the battery retains its charge and enters maintenance mode, it indicates that the automobile is becoming active and experiencing a power loss.
 

[TechWhiz]

I have successfully used a trickle charger on both batteries without encountering any problems.

[clk320x4]

Initially, I only charged the front battery and everything seemed to be OK. However, I then switched to charging the rear battery instead, which seemed to be effective. However, when I removed the battery to address minor rust issues, complications arose. I left the Auxiliary battery for repair overnight and am now recharging it from empty. This will determine whether it has to be replaced with a new battery. Once this is determined, I will proceed to do the same with the front battery.

[bvlenci]

From my understanding, the recommended procedure is to charge the Auxiliary battery located in the trunk. This battery is specifically built to refill the starting battery while driving, in case the alternator has not generated enough power to restore the energy used during the start.

The Aux / Consumer battery bears the whole burden of powering the roof, HVAC, and daily operations.

It seems logical that MB would have designed the system in such a way that just one battery, namely the larger Consumer battery, needed to be charged from an external source.

Are you removing the battery because you are unable to connect it to a cable? Removing the battery generally poses the danger of resetting the increasingly complex circuitry. In modern vehicles, including maybe this one, the car's system requires accurate information on the battery's charge level in order to charge it appropriately. This necessitates a series of complex procedures, which implies that newer automobiles may need adjustments to accommodate a new battery.

(There are more knowledgeable electrical professionals who are welcome to provide their insights on the specific causes, which are typically above my level of expertise.)

Generally, it is preferable to connect the battery charger / conditioner to the automobile via a cable, rather than removing the battery.

[PixelMaster]

Prior to removing the front starting battery, it is important to first disconnect the rear battery's negative connection. This is taken from the MB training handbook.

[PixelMaster]

Regarding the process of charging from an external source..

[clk320x4]

I removed the batteries to test their ability to keep a full charge and to verify that they are not defective, as advised by OneForTheRoad.
During the night, I performed a reconditioning cycle on the auxiliary battery. This morning, I initiated a regular charging cycle on it, and now it is fully charged using the Noco auto charger. Transitioned to state supervision.
I have transferred the charger from the starting battery to the main battery, which quickly replenished it to its maximum capacity. This action also caused the charger to switch to monitoring mode.

I am aware that the batteries are in a satisfactory condition. I shall abstain from including them for the remainder of the week as a means of affirming their true condition.

Your statement on the car's need to be aware of its battery seems to be credible. I own a vehicle equipped with a 3.5-liter V6 engine and I recall a video on YouTube by a content creator called ThreePeaks mentioning the need of wiring the batteries to the automobile. This issue is most likely a result of the user's actions, as is often the case with these vehicles.

Everything was satisfactory. I was using crocodile clips to recharge the front battery when the vehicle was not in use. After seeing many instructional videos, I proceeded to connect the back battery to the charger. Everything seemed to be in order. Subsequently, I removed the auxiliary battery for a duration of many weeks and addressed the areas of rust on my vehicle. Upon reinserting it, I affixed a permanent connection to the auxiliary battery. However, throughout the charging process, it would reach the full capacity momentarily and then abruptly deplete to empty, remaining in that state until I initiated the car's ignition. Subsequently, it seemed that the activation of the automobile would revive the battery, enabling it to recharge flawlessly till the subsequent occasion when I inspected it and found the battery to be depleted once again.

The automobile was delivered without its manuals or second key, resulting in a rather uncertain connection as I am left to speculate on its operation.

[ForumGuru]

If the battery in question is the original one, then it is advisable to replace it with a new one.
There is a possibility that I have an internal defect that causes electrical connection, but when subjected to a load, the connection is disrupted.
If the appearance of the item is identical to the one I own, it is worth noting that my item has been non-functional for some years. To the best of my knowledge, its only purpose is to enable stop/start functionality, with no impact on any other functions.

[ChatMaven]

It seems that the auxiliary battery in the R231 model resembles the one mentioned by the user, but the user has the R230 model with a larger auxiliary (consumer) battery.

[clk320x4]

Indeed, my battery is the larger variant. The positive update is that it has remained well-behaved throughout the night and is now remaining in monitoring mode.