This is one of the best ways to buy a battery for your Mercedes-Benz - Call 1-800-FOR-MERCEDES and tell them you need a battery. They'll send a guy in a truck, who will remove your old battery, install the "correct" new battery, synchronize all your electronics, and haul away the old one - all for the retail price of the battery. That's right, no delivery fee, no installation fee, nothing other than the price of the battery. That's for any Mercedes-Benz. They don't care if the car is 4 years old or 40 years old. They also don't care if you're the original owner, what day it is, or what time it is. If your battery dies and you don't want to buy one, Mercedes-Benz roadside assistance will properly jump-start your car. Did I mention this was free? Well, almost free. The caveat is they only do this for Mercedes-Benz vehicles. These guys will also bring you a few gallons of fuel or change a flat tire using your spare, all free of charge. Note: you'll pay for the gasoline, but there is no "service charge". If every manufacturer was like Mercedes-Benz, companies that sell roadside assistance insurance would be out of business.
If you decide to buy a battery and install it, get a good one. Don't go cheap and find yourself stuck in minus 20 degree weather, or on the side of the road when it's 115 in the shade. How do you tell whether a battery is any good? The most important features to look for will be dependant on where you live. If you live someplace cold, it will be cold cranking amps. If you live somewhere hot, it will be reserve capacity.
Cold Cranking Amps are commonly listed as a battery's CCA rating. Cold cranking amps are the discharge load, measured in amps, that a fully charged battery at 0 degrees F can deliver for 30 seconds, while maintaining a voltage above 7.2 volts. Every car has a cold cranking amperage requirement. That requirement can easily be seen by looking at the sticker on the original equipment battery in your car. The battery will have the word "Kaltstarstrom" followed by a number The literal translation for Kaltstarstrom is "cold start current". Based on the tag on my battery, mine has 450 CCA. If you no longer have the original equipment battery, you can ask your dealer's parts department. In colder climates, the higher the cold cranking amperage rating, the lower your chances of getting stuck someplace and freezing to death.
In hot climates, buying batteries with double or triple the original cold cranking amperage rating is a waste of money. That's because in hot climates, reserve capacity is king. Reserve capacity is frequently referred to as RC. Reserve capacity is the number of minutes a fully charged battery at 80 degrees F can be discharged at 25 amps until the voltage falls below 10.5 volts. More RC is better, even in cold weather. For example, if your car has a 360 cold cranking amp requirement, then a battery with a 450 cold cranking amp rating with a 120 minute reserve capacity is much better than one with 850 cold cranking amps and only a 90 minute reserve capacity. Why do you need reserve capacity? Because something has to power your clock, alarm, courtesy lights, delayed headlamps, radio, and all those other electrical gizmos that require power after the car is turned off.
So what else is important?
If you absolutely, positively insist on changing the battery yourself, here's one way to do it without having to reload the security code in the radio, re-sync the express windows, reset the memory in your seats, reset the sunroof, and clear the ESP error - a charger can be connected to the hot wire under the hood before disconnecting the battery in the trunk. After the new battery is hooked up, disconnect the battery charger. The car never actually lost power, so there was nothing to reset.
The red arrow points to a cover. On a CLK, there is a hot wire underneath where one could make the positive connection. The positive wire is in different places on different models. The negative can be hooked to just about anywhere else.
If for some reason the power supply is interrupted (battery disconnected) the windows, seats, BAS/ESP, and sunroof can be re-synched as follows:
The clock and radio will have to be reset as well.
© 2007 Marcus Blair Fitzhugh