I had a problem, earlier this week with a battery with real low voltage on one of my cars.. Much to my suprise it still started the car. It was an Optima Red top, it’s sealed and made differently than the regular lead acid batteries. I don’t know if they would be ok in ML’s or not. When I replaced my ML’s battery I bought a large Interstate lead acid battery, Interstate makes Optima, too, or the company that owns both makes them.

Do you think you should check and see if you have a voltage draw greater than normal when the car is just sitting? You might want to check that out and also check to see if the alternator is charging the battery properly.

Here’s the thread that contains my posts about my low voltage problem on the car I mentioned above. I did order the PriorityStart product made reference to in one of the posts. It will disconnect the battery from the load, ie car, if the voltage on the battery gets below like about 11.9 volts that way you can start your car as the battery will not be completely flat. Seems like a good product for cars that are driven infrequently.

http://forums.rennlist.com/rennforums/showthread.php?s=&threadid=133118