juris335

Here is the new generation AGM battery -today installed by the dealer in my 535. We have not found anyone who has had a dead battery when using this VRLA battery. It is not covered by BMW warranty. My dealership had never heard of it until I advised. As a measure of good will ( I bought 2 new BMWs in the past year) they agreed to place this new gen battery in both at no cost.

BMW is now using a different type of battery so know that this isn't what your other cars have. AGM stands for Absorbent Glass Mat, or absorbent glass-fiber fleece. VRLA as it is also known means valve-regulated lead acid, or a lead battery with a pressure relief valve. In contrast to conventional lead-calcium batteries, the sulfuric acid in a battery with fleece technology is not held as a liquid in the battery housing, but rather it is completely bound (100%) in the glass-fiber fleece (separators). This gives increased security against the acid escaping and thus reduces the environmental risk. For this reason, no acid can escape if the battery housing is damaged. In addition, the AGM battery is sealed to be airtight. This is possible because the gases are converted back into water by the permeability of the separators. AGM batteries differ from conventional lead-calcium batteries in their environmental compatibility and their retention of gases during charging.

When a vehicle battery is charged, the electrolysis process emits the gases oxygen and hydrogen.

In a conventional lead-calcium battery, these two gases are released into the atmosphere.

In an AGM battery, the two gases are converted back into water: The oxygen created at the positive electrode during charging moves through the permeable glass-fiber fleece to the negative electrode, where it reacts with the hydrogen ions that are brought in with the electrolyte, to create water (oxygen cycle). In this manner, the gases, and thus the electrolyte, is not lost.

Only when the gas production is excessive, that is when too much pressure is generated (20 to 200 mbar), does the pressure-relief valve open, thereby allowing gas to escape while also preventing entry of atmospheric oxygen. Because the pressure in the battery is regulated by a valve, the AGM battery is also known as the VRLA battery (valve-regulated lead acid).

At least 15 dealerships in the USA have installed these batteries and to my knowledge no dead batteries were experienced by the customers who posted follow up. Some members have been members for several years.

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turboawd

are these batteries similar to how the optima batteries are made?

vwvwvw

Sounds inexpensive.

GregBrand

Is it the absorbent glass mat? The 90Ah instead of the "factory battery's" Ah? The 900CCA instead of the "factory battery's" CCH? I'd love to know the science behind why the new AGM battery does not drain to a point that one cannot start the car.

Since I have installed the new AGM I have had no "failure to start" episodes even though my "drving profile" has not changed. This does not mean I have not had "battery drain". I assume I still have battery drain but the AGM battery, for some reason, has the capacity to handle and recover from the pernicious drains.

bloomjbmw

Great Post juris335! Thanks for the detailed information about the battery technology. One question I have is how do our cars differ from other vehicles with regards to battery issues? For example, in a typical car battery I get 7+ years (in SC where cold weather isn't frequent) and in the case of my Miata, which uses a Sealed Battery (Westco) I get 4 to 5 years depending on the driving profile. Is the E60 different because of the design of the car's electrical system -> aka it has many small devices constantly draining it even when its "off" or is there something else I am missing?

Thanks again for the post.

porsche911targa

How much are these batteries?

vkhong

Battery AGM 12V 90AH/900A AGM 90AH 900A 1 61217553954 $246.00

Howitzer

Not a bad price, either. You're saying these last for how long?

BAK530dat

I have the same experience. One year with an AGM battery now, and no problems at all. Before that I had several issues with battery drain.

tooltec

How come? It carries a BMW part number!