Hey, All.

2005 CLK 500 Cabriolet.

In 2017, i had to enter the car via the mechanical key, and the fob inserted into the dash would only trigger some dashboard lights, but there was no ignition at all. I ended up replacing that battery after i jumped it once, and then it went dead again. That battery was in the car when i bought it in 2012.

Fast forward to now.... I was out of town for two months, and returned to a completely dead car. Not even a trickle of juice was evident.

So, the question now is, does that complete lack of energy mean something? I assume (with total ignorance) that zero activity for two months is more likely to completely drain the battery than a week of inactivity, but is there a point of 'no return?' Does the length of idle time have anything to do with whether or not it's going to return to usable condition with a jump?

re: warranty — i think batteries have three year warranties, right? Mine would have been installed in April 2017, so it's a few months past 36 months. Any reason to think i could still appeal to the company? There have been some sad circumstances.... Covid, and then i was away for my father's hospice, death, funeral.... But, i doubt if 'sympathies' can be relied upon.....

Thanks for your counsel....

 

I would jump the battery and let the can run for 20-30 minutes; if it restarts after shut off put it on a trickle charger for 24 hours. You may have a drain on the battery even with the car off and the key removed. You may also have a problem with the alternator not charging the battery enough when the car is running. The car could be driven 40-50 miles without any problem with a fully charged battery and a completely inoperative alternator. Three years is not very long for a quality battery. If you replace the battery use an AGM battery that is rated at OE specs or better.

There are a couple of threads denoting what the battery voltage readings should be under operation and when not in operation. These readings can indicate if the battery or alternator are at fault.

If the car starts and runs ok under normal circumstances where it is used at least every 2-3 days, you can start looking for what is drawing current when the car is off; start it every few days; or disconnect the battery when you plan to not use for more than a few days; or connect a trickle charger when you plan to not use it for more than a few days.

 

@Fatz Thank you, sir.
I did get the successful jump—very quickly, no problems. But, we found corrosion on both terminals. The mechanic said that meant a cell in the battery was defective, and that the battery would not last long. Nice guy, and i took him at his word, but then later, i read online that this corrosion isn't all that abnormal, and the recommendation is to clean it with a wire brush and a baking soda+water solution.... So, i don't know....

 

Glad to hear you are operational again. I occasionally clean the terminals on my truck and sometimes on a tractor. I just use a stiff brush for the most part and a screwdriver. They clean up ok and don't exhibit a problem before or after the brush off. That corrosion may be more related to being outside for those vehicles.
Take care.

 

Thank you, friend. Yeah, when i first saw it, i thought it was something the mechanic would just clean off before jumping it. But, he 'made me' a bit paranoid with his certainty that a cell was defective. I'll take the car to a distributor of the battery brand and have them test it, and maybe get them to clean it.

Thanks again—