I reserved a battery at Pep Boys. But when I went last night they were closed (service was open though, which didn't help me). So this morning I removed the battery from the E55 and brought it so I could get my core charge back at the same time. Couldn't find a date code on the battery.
At the store they were like "oh, it's Mercedes, it must be original." Right, because clearly no one would ever buy an OEM battery for their used car. Well, I guess that's not that common...
The guy said "what was your discount online" and I said 15%. He said "I'll give you 20%." Sweet. I also had him test the old battery. It was pretty crappy though technically the machine didn't say "replace battery." But maybe this is what happens to AGM batteries. They just....lose capacity. The car always cranked slow and had no reserve capacity so this will be nice.
I also bought a battery brush and some of that red spray stuff that I've never used before.
Battery removed
I also decided to relocate the ground side of my battery tender harness. It is supposed to be on a vehicle ground so when the battery charges, the battery monitor sees the current and that helps it understand state of charge better, or something. So I snuck it behind out of the module mounting screws. Nice.
So how does it work? Well I left it charging while I worked on the oil leak stuff. It wasn't until much later that I actually hooked it up. But MAN does it crank great now. It cranks like it is supposed to. This thing clearly needed a battery. Check.
On the way back from Pep Boys I did stop at Mercedes to get a few underbody cover bolts and those nuts.
He said this was like the cheapest parts order he's seen. Still, it was only 3 bolts plus 5 nuts. As he was handling them he was like "these might be aluminum or something." I said "really? That must be why the car is so light." Ha.
Also they are magnetic so clearly not aluminum...