Replacing A BMW Battery

Last updated: October 16, 2017

You would think that replacing a battery in a car would be one of the easiest things you could possibly do. Not so for the BMW apparently. I have a 2005 525i E60 BMW and in my research for replacing the battery I came across a tonne of conflicting information.

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Supposedly according to the owner of a tire center near me, BMW’s have a smart charging system that determines the best output for your battery ensuring that its life is prolonged. Honestly, given how expensive everything else is with a BMW, I believed it at first.

I even called a couple of BMW dealerships and they also told me that batteries need to be installed by BMW. The prohibitively high cost of the battery and installation is a deterrent. I did not know who to believe. I can only imagine BMW probably even advise against changing your own oil.

In BMW’s apparently the battery has to be registered with the car. The computer needs to be told there is a new battery or it will assume the older and potentially faulty battery is still there, possibly overcharging it and shortening its life. Or not charging it appropriately and shortening its life by running it too low.

What really struck me as strange is a charging system that is based off a battery being registered as opposed to reading it in real-time and determining charging rate and level. Considering everything else is so well designed, I refused to believe that BMW would create a flawed charging system based on a new battery needing to be registered.

Then I encountered another potential roadblock. Apparently completely disconnecting the battery from the car is bad for the electronics. Supposedly while you replace a battery, power is meant to be maintained to the car or bad things can happen.

And on-top of that, the car needs to be re-initialised (some reporting the active steering as well).

To replace or not to replace? That is the question

This put me in an interesting situation. Do I risk replacing my own battery, potentially costing me hundreds or thousands to fix, or do I take it to BMW, get reamed on the price and have piece of mind if something screws up they are responsible?

Then I remembered a while ago I bought the manuals for my car by Bentley Publishers. Two massive books that detail every aspect of the vehicle (including wiring diagrams). In the section that details replacing and swapping battery it mentions that it needs to be registered with the car using a BMW tool.

See below for some photos I took of the pages in the book. Click on the images to see way larger versions of them for more detail.

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The manual all but confirms that the charging system in the BMW seems to store voltage settings and the state of the old battery. What many thought was a myth or money-grab from the BMW dealerships turns out to be true.

Still conflicted, I did what any reasonably curious hacker would do, I took the risk and bought my own battery. I ended up choosing the cheapest battery I could find at a whopping $269 for the Century DIN92LMF rated at 735 Cold Crank Amps (CCA).

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I pop open the boot and look for the panel on the passenger side underneath the boot covering. I then carefully remove the existing battery terminals and lift the old heavy battery out. So far, so good.

One thing I discovered is BMW’s certainly have a lot of tech in them. On-top of the battery, it is a bit of a mission getting the connectors off (there are wires everywhere) and then keeping everything out of the way while you put the new one in.

It might be helpful if you have someone with you handing you the required tools and holding the terminals/cabling out of the way while you remove the old battery and putting the new battery in.

Starting the car

The moment of truth. Will the car start, will I get error messages telling me to take the car to my dealer or will nothing happen at all?

The car starts. There are no error messages and everything appears to be functioning normally. Heck, I only needed to set the date and time again and the radio worked fine as well.

Lately my air conditioning had been doing some weird things. One moment it would be incredibly strong and blowing a tonne of cool air, the next the power would weaken what felt like 50%.

I assumed maybe the AC just needed a service, but since replacing the battery the AC has been working at full strength. Then I realised that when a battery goes bad, the BMW intelligently limits power usage to ensure you don’t get stranded anywhere with a flat battery.

Conclusion

I come to the conclusion that changing your own battery is not the end of the world, but would its life be shortened? Obviously determining this in the short-term would be impossible. You only need to program the battery into the car if you’re changing the type of battery being used, if it is the same battery, then programming is not required.

I am planning on taking weekly measurements of the car battery before I start it and comparing voltage levels. I am not saying that you should do what I did and replace your own battery, but I am saying that I encountered zero issues doing so.

I couldn’t find conclusive proof that my new battery needs to be programmed. Apparently what happens is the car needs to have its recharge voltage rate reset or it could not optimally charge up your new battery. This seems to go against basic electronics, but whatever, BMW are the experts.

Apparently BMW’s keep batteries around 80% capacity and never 100, so it will be interesting to see if the voltages remain consistent or dip. It is almost summer here in Australia, so probably the best time to find out as no cold weather will hinder temperature values or capacity.

It is also worth noting I installed the same type of lead acid battery. I considered a Absorbent Glass Mat (AGM) because they last longer and they’re lighter, but also more expensive and definitely would require registration in the car.

Do not change battery types without registering.

If after a few weeks I notice the battery is being impacted, I will take it to get registered. If not, I’ll keep things as they are. You can’t deny the $250 to do it yourself versus potential $450 or more for BMW to do it is considerably cheaper if you’re on a budget especially.


Update October 2017

I sold the car earlier this year, but the car never skipped a beat since I changed the battery myself without registering. I saw no voltage issues or other problems as a result of not registering the battery. So, who knows what registering really does?

It is worth pointing out that I replaced the old battery with a new one of the same type and CCA’s. If you increase or decrease the CCA’s of the battery or put an entirely different type of battery in, things could be different.


 

Dwayne

 

22 thoughts on “Replacing A BMW Battery

  1. OK, My buddy is going through the same thing, now.

    Did BMW really engineer a battery cable / compueter system that MONITORS the battery charge but must be registered anytime the battery is changed?

    Four months later – what changes have you seen in your cars electrical behvior?

  2. How did you reset the date and time? I can’t find the date/time under Display Setting in the iDRIVE with my 2005 E60 model.

  3. So, I just replaced the battery for a 2011 328i and it just started just fine after. Hardest part was undoing the bolt holding the battery down and in place at the bottom. Had to go to the store for an extender bar. And I needed someone to hold all the cables out of the way to get the new battery in. Heavier than you would think. What are they? Filled with lead or something?

  4. Shorten battery life and possible Alternator damage longer term is not what I call a good deal. These cars need to be probably taken care of. Just buy american or Japanese cars if you can’t afford it…That’s my advice

  5. Hi I replaced the battery on my 2005 330ci bmw 3 years ago never had any issues,every thing on the car worked as it did before I changed the old battery,so what do that say good luck.

  6. I just changed my Xdrive30d Msport’s Battery, I needed a 90ah 900cca AGM, No Worries, just keep a battery connected to the terminals under the bonnet (use good jump leads) so as it has continuous power to the system. But get a Good battery, Varta are what BMW use with there sticker on it, but Century are also good.
    And I do my own oil changes, and Fuel filter, Just get the Correct Oil (LL04) in most new cars , just depends on your car model. Do your home work and look it up. Saves me Heaps. ps being a marine engineer also helps.

  7. On another note, most models also have a micro processor connected on the negative terminal with a line leading to the positive terminal on the battery. This is the IBM (integrated battery monitor). This little unit monitors battery voltage and adjust alternator regulator output to keep the battery at optimum levels. If this little unit goes bad you battery will not maintain proper voltage and you will begin to experience started drag and no start condition. But if you are having codes everywhere and occasional do start condition followed by everything operating normal. The white elephant in the room is the IVM (Integrated Voltage Module). Nobody says much about this little device but suffice it to say that is controls everything about voltage. About 140.00 USD and 15 min to change. Both the IBM and IVM are used on BMW, Rolls, and MINI….

  8. I changed the BMW E60 535i car battery myself 3.5 years ago after research into this battery register issue. The car has seen no problem so far. I understand the battery charging voltage might not be optimized but who cares. Plan to replace the battery when it hits 4 years. From an economic standpoint, it makes perfect sense. In terms of time, I save a lot of time by doing this myself. If you have a lot of money and you don’t care about waiting an hour in the dealership, US $600 will do.

  9. Going through a similar episode. The battery would drain after 2 weeks. The shop said my 4 year old battery with a 6 year warranty was bad. The reason? Because my Interstate battery was not registered 4 years ago when installed because it was not a “smart” battery. If not registered, the BMW’s charging system shortened the life of the battery. I am still skeptical, but I am having the $425 BMW battery installed this morning. I don’t mind paying more for better technology. But seems like proprietary swindle.

  10. I just changed the battery from my 2005 X3 BMW with a non BMW battery. So far so good. I will keep monitoring everything. Todd

  11. This battery registration/monitoring I think only applies to BMWs built in the late 200x? I asked some friends and they all said their 1998-2003 BMWs have no such issue.

  12. I can’t believe how BMW drivers are happy with this ‘propriety swindle’ – (thanks Kjeld molvi). This is a luxury car, yes, but that DOESN’T mean that people who can afford these cars SHOULD pay more. Do you realize that that mentality can cause you to lose excessive amounts of money you’ve worked hard for?? The technology used in ALL vehicles today has improved so much there is not much in it. For example, KIA GT Stinger is impressive, you have to pay EXTRA for iphone/android connections in a new Ferrari… which is free in a Toyota Yaris. BMW is a luxury car that is selling you an image and exclusivity… but the technology is better in a Honda Jazz. Don’t let your ego fool you, do your research.

  13. Me too.
    It’s not that we can’t afford it, we just don’t like being grifted.
    If the amp-hr of the new battery is the same as existing, I am approaching this as “within limits”.
    However, if you change battery type or power, registration may be advised.
    I’m presently exploring whether suppliers such as Napa or similar parts suppliers can register batteries purchased through them.
    The registration doesn’t appear to be BMW specific. It appears to be process specific, meaning if you find the equipment, you don’t need BMW.

  14. I put Auto zone battery in 2005 BMW 2005 325ci and every since I change battery I’ve been getting low battery notice after one day if I don’t drive it..could it need to be rester?

  15. Took my BMW X5 to a mechanic and never have to worry or think about this issue.
    The G Man

  16. I’m planning to change my battery myself. I will use an AutoZone replacement. My mechanic wants $600. The battery is a little less than $300 new.. I will take a chance that it will not strand me for the next 9,000 miles before trading the car in.

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