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Installing new battery in 2007 Q7

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Installing new battery in 2007 Q7

Old 05-14-2019, 12:15 AM
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Posts: 80

You MUST reprogram the BEM module in the ECU when the battery is swapped. This can only be done by the way of VAG-COM.
The issue of resetting your ECU and forcing the computer to relearn fuel trim, shift points, etc is not the issue. The BEM module is what controls how the computer charges the battery. The Q7 is smart... It can adjust the alternator (generator) load based on the demands from the electrical system and the information thatís saved in the BEM module. When you swap out the battery and donít update the BEM module the ECU will NOT reset itself and assume youíve put in a new battery. The BEM information is retained and the computer will still think itís using the old battery.
The issue with this is that your car may feel like itís starting better, not failing to crank, etc, but the computer is not sending the correct electrical charging information back and forth. What will happen is that your new battery will be worn down much quicker and your battery that should last 7-10 years will crap out on you much faster.

Im not just rattling off nonsense because I was even dumbfounded at the idea of needing to reprogram a module just because I was changing out my battery, but itís true.... Consult any Audi mechanic and they will confirm that reprogramming of the BEM is required.
Interesting thing is that with some of the newer year VW vehicles the electronic steering will actually become unresponsive if you attempt to replace the battery without a VCDS.

I just came across this thread and thought Iíd chime in since I literally just went through replacing my battery less than a month ago... Ordered an OEM Varta battery from carid.com and had my local VW stealership reprogram the BEM. Battery cost me about 350 bucks and shop time about 120 bucks because the drivers seat has to come out to replace the battery.

Best of luck with your battery swap!!!
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Old 05-14-2019, 02:09 AM
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Hey Willgatlin25,
Thank you for all that great information mate, thatís pretty helpful... donít know what BEM means but guessing itís important!! Well I havenít changed or disconnected the battery yet, neither have I found the Bluetooth module, but I have an appointment with the Audi dealership or stealership as you put it (lol) on Friday morning, so weíll see how it goes...
Iíll update this thread then!
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Old 05-14-2019, 02:53 AM
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Wish I has more hands on knowledge with the Audi computer systems.
All I know is having spoken to multiple German auto mechanics, including the dealership, I was warned not to attempt the battery replacement myself unless I had the knowledge and access to a VCDS (Vag-Com Diagnostic Scanner).
The BEM is a specific code that is included on the OEM replacement battery. Non OEM batteries will likely not have this code and if you arenít dealing with the dealership or an Audi experienced mechanic, they may have trouble knowing how to program the system to accept the new battery. The BEM code is just that, itís just a code, something to tell the BMS (Battery Management System) that a new battery has been installed. The actual code itself has nothing to do with what the BMS system does, it just simply tells the system what type of battery you installed and if itís a valid BEM code (Meaning from an OEM battery) then the BMS system has preconfigured parameters that will be updated which changes the electrical commands between the BMS and the ECU (Engine Control Unit). In simpler terms, it updates the computer to let it know what type of battery is installed in the vehicle and clears out its old learned parameters so your new battery is charged properly and your alternator (generator) isnít under or overdriven. Most importantly, from my perspective, is by updating the BSM with the new BEM code it wonít destroy my brand new expensive battery by under or overcharging based on old learned parameters.

Now, to make things even more confusing- Within VCDS (Vag-Com Diagnostic Scanner) some newer Audi vehicles are able to access the UDS protocol system directly. With access to the UDS protocol system you can actually manually program in the cranking amperage and other important information about the new battery which allows you to get away with using a non OEM battery and not screw up the BMS or damage anything. Having said that, with such an expensive vehicle I would not personally take any short cuts especially with something as simple as the battery.
ALL Q7 vehicles, to my knowledge, are equipped with AGM (Absorbent Glass Mat) batteries. They were and are still built with extremely high demand electrical systems and very expensive components. If Audi designed these vehicles to operate with specific batteries and went so far as to dedicate a computer system just for battery and electrical management, then why would you want to shortcut around it to save a buck? Not to insinuate that you or anyone else is attempting to do so, but I have seen many many many other comments on other forums where people have claimed to just swapped out the battery themselves and ďeverything is fineĒ. Or, they bought a battery off amazon for ďhalf the cost of oemĒ and no problem. Only to see them come back and update on their own posts only a year or two down the road stating that their new battery is suddenly dead or multiple electrical devices in their vehicle has started failing. Well....was trying to save a couple hundred bucks worth it? I should think not....

I had quite a few instances, before I had my battery replaced, with certain components acting strange such as door handles not unlocking the car, dome light not turning on from the drivers side but only responding to the passenger door... Rear hatch not responding to the remote control open command at random times.... Let the car sit for 48 hours and the engine wouldnít start... Randomly having the yellow low battery light turn on while driving!

Needless to say every single one of those issues was corrected when I had my battery replaced and the BSM system updated to reflect that the new battery was installed.

Im curious to ask what you end up paying to have your battery replaced and what route you decide to take to have the work done? Not sure where you are located but Iím in Washington State, USA. I looked up exactly what I paid for my battery and it was $355 USD including tax, and $185 USD including tax for the install. So total cost to me was $580 USD for the OEM battery plus install. Mind you I did not purchase the battery through the dealership, I purchased the direct OEM Varta battery from carid.com. Dealership quoted me $446 for just the battery not counting install, so their parts markup was significant. Like I said, as long as you get an OEM battery youíll be fine. Either buy through the dealership and deal with the markup or purchase yourself and bring it in, but I highly recommend sticking with the OEM battery!! Your local corner auto parts store wonít carry it, donít even waste your time lol.

Let me know how it works out. Best of luck.
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