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Problem with R230's trickle charging


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I own a 2007 Sl350, which I acquired as a temporary automobile. It is not often used, similar to many other SL's. 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 amount of corrosion in the trunk, so I removed the auxiliary battery and performed the necessary repairs. After reinserting all the components, I attached 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 or a complete depletion of the battery. When the remote becomes unresponsive, I am compelled to physically unlock the vehicle using the key. Upon starting the automobile, all components immediately become active and functional. The battery charger seems to indicate a momentary pause. No, I am not entirely flat. In fact, I possess a green hue. Can you observe? It then resumes its usual behaviour till it repeats the narrative once again.

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

Has anybody seen something comparable? I must clarify that I own a S Coupe and share the charger with it, and it works well in that vehicle.

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Totally ordinary.

This topic has been extensively addressed on this platform. If an R230 is not used for a month, there is a gradual discharge of the Auxiliary battery, which is designed to safeguard the starting battery. After driving the vehicle for around ten miles, the Auxiliary battery will reactivate, allowing you to power the hood, air conditioning, and other systems.

The next step is to thoroughly recondition and recharge your auxiliary battery to see 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 provide a little amount of energy to your auxiliary battery.

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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 function well until I removed the battery to address some rust on it. 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 can proceed to do the same with the front battery.

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Based on my understanding, the recommended procedure is to charge the Auxiliary battery, located in the boot, since it is specifically built to refill the starting battery while driving if the alternator has not generated sufficient energy to restore the energy used during the start.

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

It seems logical that MB would have constructed 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 a wire to it? Removing the battery generally poses the danger of resetting the increasingly complex circuitry. In modern vehicles, including maybe this one, the car's system need accurate information on the battery's charge level in order to charge it properly. This necessitates a series of complex procedures, which implies that newer automobiles may require adjustments to accommodate their new battery.

(There are more knowledgeable electrical professionals who are welcome to provide input on the specific causes, which are normally 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.

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I removed the batteries to test their ability to retain a full charge and to confirm that they are not defective, as indicated 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 to the starting battery, which quickly reached full capacity and thereafter switched the charger to monitoring mode.

I am aware that the batteries are in a satisfactory condition. I shall exclude them for the remainder of the week as a means of verifying their true condition.

Your statement on the car's need to be aware of its battery seems to be credible. I own the 3.5 V6 engine and recall the individual on YouTube from ThreePeaks mentioning the need of coding the batteries to the vehicle. This is most likely totally self-inflicted, as is often the case with these autos.

Everything was satisfactory. I connected crocodile clips to recharge the primary battery when the vehicle was not in use. After seeing many instructional videos, I proceeded to connect the back battery. Everything seemed to be in order. Subsequently, I removed the auxiliary battery for a duration of many weeks in order to address and resolve the rust areas on my vehicle. Upon reinstallation, I affixed a durable connection to the auxiliary battery. However, throughout the charging process, it would reach full capacity and then abruptly deplete to empty, remaining in that state until I started the car's engine. Subsequently, it seemed that the act of starting the automobile would revive the battery, allowing it to recharge flawlessly till the subsequent instance when I checked 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.

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If the battery in question is the original one, then it is advisable to replace it with a new one.
I may have an internal malfunction that establishes contact, but when subjected to a load, it interrupts the contact.
If the appearance of the item is identical to mine, it is worth noting that my item has been non-functional for some years. To my knowledge, its only purpose is to enable stop/start functionality, without affecting any other functions.

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