This applies to a 2021 P300 and may apply to others.

Translating the battery code on my factory battery showed the battery was built over a year before the car's build date and the voltage tests were showing a battery in decline.

This 4 pot car had the H7 battery whenn new.

Comparing the specs, the height and width for the H8 are identical. The H8 is simply longer.

The H8 has more cold cranking amps, more capacity, more amp hours, more weight, more EVERYTHING.

The battery tray in this car had a small stop bracket spot welded to the aft side of the battery tray.

A cold chisel easily pops this bracket off. Smooth off any burrs and install the H8 BCI Group # is 49.

These cars place tremendous demands on the battery and I'm happier with the additional capacity.

BEST !

RWS

 

Interesting that most owners on here are looking for less weight, not more!

At the risk of jinxing mine, my 2017 battery is still fine after 6 years.

 

Weight???

Weight till I get that Dynamat in the doors, floor & trunk . . . .

BEST !

RWS

 

My battery is dated '13 ! Still fine.

 

On the other hand, the battery in my MY17 died 3 years ago, even though the MY14 was still going strong. I might have gotten another year out of the older one, but weighing the time value of spending $200 a year "early" vs the PIA of being stuck somewhere at an inconvenient time, I replaced it preemptively.

Good thing it doesn't rain in the UK.

 

Shhh! You'll make people jealous!