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Your battery has an IQ… of a genius

Written by maryp posted on Friday, October 10th, 2008

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Every once in a while, someone calls us telling us that they have replaced their own battery in their later model BMW and are now “stuck”. You did what? You went where…to get a battery for your beautiful, awesome, technically perfect BMW?

The later model BMW’s battery size is coded in the DME. Your replacement battery must be the same capacity rating as the original battery. Now if you are looking for a cheap “fix”, you may be tempted to try something that is not OE at your neighborhood auto parts place. But, be prepared for other issues down the road, because that’s what coming at you. Not trying to be pessimistic, but just a realist. Yes, the modern BMW has drastically changed and the days of just “throwing in a new battery”, are a distant memory.

There are a few good reasons that you probably don’t want to change the battery yourself. For example, the battery cables and the IBS, (Intelligent Battery Sensor), must be handled properly and with care, (and knowledge) to avoid irreparable damage. BMW’s Intelligent Battery Sensor has a micro controller that is measuring Battery acid temperature, terminal voltage and the charge/discharge current. In BMW terms it is measuring the state of health and the state of charge and sending that info to the DME. (It does this about every 40 seconds, actually when the key is in the off position). Three functional aspects of this unit are mechanical, the software and the hardware elements. Each one of those different elements perform as few as 3, to as many as 9 functions. But, it is just one unit. How cool.

In cases where your DME needs an update, the IBS may need to be replaced. The software in the DME and the IBS must match. Go figure. But, don’t try this at home.

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