How do I buy a replacement battery
I own a 2003 MB E class E-320. It needs a new 800 CCA battery. The dealer wants $500+ for that, AutoZone has a 900 CCA for $220
The question is: Do I need to buy a dealer battery for my car? If I won't have to go there, can I replace it myself if I buy it from the parts place?
Check if your car battery needs to be “registered”. It’s basically just resetting the computer on the car.
If it needs to be registered, you will need a scan tool that can handle the registration.
If it doesn’t need to be registered, you can mostly likely change it yourself.
Check your owners manual for more details.
AutoZone has a 900 CCA for $220
I don't know your zip code but in my area I just checked and Costco has this battery for $185. And it's Costco so they stand by what they sell. From my experience with them if you have Costco membership buy it from them.
And if the only part is needing a fancy scan tool after changing the battery maybe you can buy battery and have your trusted independent mechanic change it for you. But if like @dad2lm2 said above it's some programming dealership only can to do then I guess unfortunately you might be stuck with that option.
The Autozone battery should be just fine (you can check the "group size" to be sure). To a large extent, a battery is a battery, so as long as it has adequate amperage (which that one does) and fits in the spot (which the group size tells you) you should be fine (though most new cars also specify an AGM battery these days).
[I had a similar situation a few years ago with my mother in law's Lexus. The dealer wanted some astronomical $$ for the brand name battery. Her car had some obscure size that hardly anyone but Lexus uses, so it was about impossible to find that exact one. But I was able to get one from WalMart that was the same specs but with the terminals on opposite sides. I just made sure to hook up the positive cable to the positive terminal, and it has worked just fine for years.]
The issue is likely to be getting all the electronics reprogrammed after you install the new battery. @kaizen is right that you might want to check the owners manual before you install the new battery and make sure that Mercedes didn't make it so that you have to have the dealer reprogram your stereo or something (Mercedes likes to pull that cr@p).
The OEM battery will probably last the longest. But you don't need to buy it. Just make sure it's the correct size and that it has a good warranty