Jump or Replace battery?
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....




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.
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....




Take care.
Thanks again—



