Steveo1966

So I went to start my car late yesterday afternoon (it had been sitting about 3 weeks) and it would attempt to turn over but wouild not actually turn over the engine. I have been suspecting a weakening main battery for a few months now, and then I was getting all kinds of intersting and concerning messages on the display... all symptoms of a voltage/battery issue I suspected. Even attempts at boosting from a battery back, then another vehicle (Audi Q5) wouild not help. Still suspecting a battery I took my wife's vehicle out to get a new one, but could not get to my dealer in time. That said, the dealer parts team, based on my VIN, gave me dimensions over the phone for the actual replacement battery called out by Mercedes, which were H6 dimensions and not the H8. Based on this I picked up an H6 battery from a parts retailer since the dealer was closed at this time. Last night, when replacing the battery, lo and behold, the battery in the vehicle is the longer H8 battery, and OEM mercedes as well, so I suspect that is the original battery. In any case, the H6 easily dropped in as a replacement and as soon as I reconnected everyting, the car started just fine, and all is back to normal, and no concerning messages.

I realize that there is less capacity in the H6, but for a vehicle that I do not plan to keep more than 2-3 years or so, is there any harm in continuing with the H6? I am not sure the retailer will allow me to return the H6 for credit and upgrade to the H8. The H6 is rated at 760 CCA vs 900 for the H8. And those specs are for the new Energizer H6 & H8. The OEM H8 mercedes battery that I pulled out is rated at 80Ah / 800A, so just marginally more than the new H6 right. I am in Toronto area but the car is always kept in an insulated garage that never gets below about 5C and is typically at 10-12C, so the car almost never is subjected to a sub-zero start.

Thanks in advance for any insights.

kajtek1

I don't think you are getting extreme cold in Toronto, so H6 should be all you need.
Most of European models go with H6 as they don't have power seats, 1000W stereos and lot of other gadgets.
I bought my H8 battery at Costco for about $180 and testing it with my Solar tester show it way above specifications.

Steveo1966

Perfect, thanks for validating my thinking. And yes, my H6 Energizer was purchased at Costco, and over specifications as you say.. and pretty close to the 2016 OEM H8. Thank you!!