Dnasty

I recently went through probably my 4th h7 battery under warranty and was wondering what battery the car calls for in 2010 the place that keeps changing it seems to think h7 is the size and I’m not surprised because that is an exact fit with the bracket. I noticed that many places seem to show an h8 but it will not fit in my battery compartment with the bracket (I would have to remove the bracket then there would be movement). I also noticed a trey in the trunk that is shaped for holding what is probably an h8 but was never occupied since I purchased the car and has no cabling to it. I assumed it was for cars that had airmatic or some other premium feature. Could a smaller battery be cause for premature failure?

oldmots

This car can get an oil leak in the oil cooler right above the belt tensioner that will cause the belt to get oily and slip on the alternator pulley, just check it before replacing any more batteries. I had this problem and after fixing the oil leak, I have had no more battery problems. By the way, an H7 is not a small battery.

Dnasty

What sort of battery problem were you having from this? Also I was just saying h7 was smaller than h8. Which size does yours take?

oldmots

The coupes use an H7, the 4 doors use an H8. The problem was the battery kept losing its charge and I would replace it thinking it was bad. It was not, the charging was just sporadic.

Dnasty

interesting it must have been a pretty bad leak. I’ve been using the little hidden menu screen on the dash that shows you the voltage and amp draw. Pretty cool feature. I think it’s a bad battery because it’s showing about a 10-12amp draw when the key is in position 1 and the voltage drops pretty quickly.

CaliBenzDriver

It's time to stop and take a deep breath. I can you say it's a bad battery after 4 of them?

I don't think the problem is a defective battery by now.

Something is causing this upset:
either discharge or lack of proper charge.

The net result is an exhausted battery, right?

Dnasty

Well what could it be?

CaliBenzDriver

What sort of symptoms or complaints are you after figuring?

Does the engine charges normal voltage into battery.... 11.0; 12.0; 12.6; 13.7: 14.4: 14.9V ?

Does the car drains the battery while stopped... how long...: 1 night, 3 nights, 2 weeks, 1 month?

You are ahead of the pack because you already know how to display your battery Voltage + Current data on your cluster.
Pay attention to it and report both data during normal drive so I can help you make sense of it.

Use an automatic CTEK float charger to get your battery in top condition and keep it there. Then we'll see if your car abuses your battery.

604550C207

Hey,
I don't really know my way around cars, but I'm trying to learn as I go.
This sounds like it could be a possible cause of my battery drain issues.
Would you mind taking a couple pics to point out exactly what parts you are referring to?
Thanks!

Chevota

That depends on the engine but its hard to miss the belt. Then see if the ribbed side of it seems dry or oily.