“What the heck are you doing putting a Walmart battery in a Mercedes-AMG?” my trusted independent mechanic, Shir, inquired over the phone the other afternoon. To answer that question, you should probably read on about yours truly trying to save a few bucks on his latest project car.
What had happened was…
Earlier this year I found a very low-priced 2005 Mercedes-Benz AMG E55 for sale. I knew the used 100,000-mile car would need some work to bring it up to my expectations, but the price was right, so I purchased the 469 horsepower (and 516 lb-ft of torque) super sedan with a significant repair budget set aside. One of the ways I figured I could save money on needed repairs was by replacing the dying battery with an aftermarket one I’d learned about on the Mercedes-Benz MBWorld.org forums. Man, was that ever a mistake.
AMG’s potent 5.5-liter V8 requires a big boy battery capable of generating at least 900 CCA (cold cranking amps). I had read on the MBWorld.org E55 AMG forum threads that many owners used a Walmart solution to save a couple hundred bucks and still get the same performance. What I failed to research (and what many shade tree mechanics failed to mention) is that there is a HUGE difference between lead acid batteries, like the EverStart Maxx model I purchased, and the AGM (absorbent glass mat) variety Mercedes-AMG specifies. Chiefly, the AGM battery performs better with vehicle systems that rely heavily on complex electrical accessory systems. Also, massive temperature fluctuations don’t hinder AGM batteries as much. Garaged in the Washington, D.C. area, it’s not uncommon for my E55 to experience 80-degree temps on a Monday, then 30-degree temps the following evening. Blame Al Roker or global warming–all I know is that those type of swings decimated my cheapy $134 Walmart block.
I should have known something was up with the lead-acid battery I had dropped in the beast when after only a few miles on the odometer, the SRS airbag warning light came to life. In denial it could have been the result of an ill-spec’d battery, I reasoned since the E55 was 12 years old, the airbag probably needed to be replaced, so the warning light being triggered wasn’t outside the realm of normality.
Here’s what I bought from Walmart.
A few months later (and after the car endured a flawless 500-mile roadtrip to New York), the vehicle would not start. Hell it didn’t even respond to the keyless remote fob buttons when I pressed them. My Autobahn sled was deader than dead.
I jumped the car back to life, only to read a bright red message on the dash which said, “Take Vehicle to Workshop.” Dammit.
What I should have bought all along…
After paying the pricey bill for a correctly spec’d AGM battery my mechanic recommended, along with replacing the burned out parking light bulbs (who knows if those were the result of the wrong battery being used), my “Silberbomber” as it’s affectionately known to me, is running like a champ, with no error codes and no problems starting in the cold. Oh, and in case you are wondering what exact battery my mechanic Shir from German Auto Diagnostics installed, check out the Interstate MT5-49/H8.
Full Disclosure: German Auto Diagnostics has discounted labor in the past for marketing and editorial services by the author. The author only recommends honest, dependable service and German Auto Diagnostics fits that editorial requirement.