Unusual Battery Performance

[Rudy7831]

The 2007 ML 63 Japanese import I just acquired had remained stationary for a week, connected to a trickle charger while I was familiarizing myself with the new head unit (still in the process...), but had not been operated otherwise. Last Monday, I attempted to deliver it to Terry Gates for tailgate repairs, but the electrical system was completely nonfunctional—no unlocking, no illumination on the dashboard, and the key would not turn in the ignition. I effortlessly jump-started it using the other ML, then drove it to Harrow, which took around thirty-five minutes. It was not charged throughout the period it was being serviced, and I retrieved it on Friday. It began satisfactorily.

The importer asserts that they installed a new battery, and I believe this assertion to be accurate. The inquiry is if a brief duration of somewhat more than thirty minutes suffices to totally recharge a depleted battery, or whether the electrical system is designed to deactivate at a certain voltage to avert total battery drain.

[Black_raven]

More knowledgeable individuals will provide you with the exact figures soon, but the heuristic I have always understood is that around eight hours of driving is required to recharge a fully depleted battery to an effective full capacity.

This is nonsensical, since it will differ from vehicle to vehicle, drive to drive, and battery to battery.


This negates the notion that a thirty-minute run (or two thirty-minute runs) suffices to recharge your battery to its maximum capacity. ("Sufficient to initiate the vehicle a second time?" Certainly)

Unresolved inquiries:

Why was the battery depleted if it had been trickle charged? Are you implying that you just performed a trickle charge when interacting with the head unit, rather than for the whole week?

What is the date inscribed on the battery that they purportedly installed?

[Rudy7831]

It was charged just by trickle while I was using it.

The battery is located behind the driver's seat, making it difficult to access, therefore preventing me from verifying its date. The importer, without prompting, informed me that accessing the battery was quite challenging, particularly since they initially searched for it beneath the passenger seat. This suggests that they researched the procedure for a left-hand drive vehicle and confirms that the battery has indeed been replaced.


What was the reason behind its flatness? I am uncertain. Terry Gates proposed that the malfunction of the tailgate might have resulted on a battery depletion.

After standing overnight for eighteen hours, it displayed 12.51 volts at the charging terminals under the hood today, indicating it may be functioning properly presently. I am monitoring it closely.

[Rudy7831]

After twenty-four hours, it has decreased to 12.44 volts. The voltage decrease is 0.07 volts; although this may seem little, if my battery charge chart is accurate, with 12.5 volts indicating 90% charge and 12.42 volts representing 80% charge, I should maybe be rather worried.
 

[BENZE220AMG]

In my experience, a surface charge, such as a brief excursion to Wayne Gates and back, seems to dissipate rapidly.

I recommend completely charging the battery before assessing the voltage decline over time.

[MidnightMarauder]

Indeed, connect it to a CTEK or a comparable charger until it indicates a full charge, leave it overnight, and assess its condition the next day.

[Rudy7831]

I was previously unaware of it, but the Ctek has been operating for just seventy-five minutes and has reached Stage 7 (Float). Strangely, the voltmeter indicates only 12.98 volts between the Ctek terminals and the charging posts, although it should register 13.5 volts.
I believe there is no cause for concern, given the rapid charging of the battery.

[Rudy7831]

12.61 volts after an overnight period of inactivity. That will suffice enough.