Laura and I purchased this vehicle in 2009 and we’ve yet to change the battery. I was very nervous last winter when the temperature was below zero. When I went to start the car a few times, I noticed that it had just a tad more difficulty turning over than it did during the more mild months. I knew the battery was getting old and I made a note to buy a new one. The thing is, winter was almost over and the car continued to start just fine. I decided to ignore the issue until it got warmer outside.
Let’s fast forward to earlier this week. The nights are getting chilly once more and I still haven’t changed the battery. Things seem pretty much the same when it comes to starting the car. Now I’m getting more nervous than I was last winter because it’s going to get damn cold real fast and I don’t want to be stuck somewhere with a dead battery. It’s also seven years old. How long do these things last anyway? From what I can gather, about a year and a half if you live in Florida and anywhere between five and seven if you live in Maine. It’s the hot weather that kills batteries.
It doesn’t matter. It’s got to be done. I don’t like surprises.
Now, let’s fast forward to today. Laura and I took a trip to Sam’s club on Monday and purchased some food. I also grabbed a Duracell battery for the car. I had intended on them installing it, but the kid behind the counter made me think twice about that. He said he never worked on a BMW before and before he could even finish his second sentence, I told him that I’d simply purchase the battery and do the job myself. They offer free installation, but I was under the impression that someone who knew what they were doing would take care of things. I didn’t think it would be the kid behind the counter. I bought the battery and brought it home.
Since today was rather warm in the mid-fifties and was wasn’t raining or anything, I figured it’d be a good time to work on the car. I’m so used to doing things in the dark and at 20 degrees that this was a treat. And after watching a few videos to warm me up for the task, I didn’t think I would run into any issues.
From here on out in this post, I’ll be talking about the installation of the battery in the car. Towards the end, I’ll discuss an option you have when it comes to registering the new battery with the vehicle.
In most BMWs, the battery is located in the trunk. If you look at the photo below, you’ll see that in our case, it’s in a compartment at the passenger side corner.
I twisted the small black knob and pulled the compartment cover loose. I placed it in the trunk somewhere just to get it out of the way. This next photo is the original battery installed in its proper location.
There aren’t all that many things to unscrew when it comes to changing a battery in a BMW. It looks intimidating, but from what I found, the biggest challenge was keeping the wires out of the way when it came to actually pulling the old one out and dropping the new one in.
This is me unscrewing the bolts that hold the top bracket into place.
In this next photo, I removed the distribution panel (red cover) with a 13mm socket. If I had it to do over again, I would have left this attached and simply disconnected the negative terminal first and then the positive. There’s no need to remove this panel independently.
After this, I removed the negative terminal and then the positive. On the positive side of the battery, there’s a small tube that sticks into the battery itself. I pulled that vent tube out. I also unscrewed the bracket that holds the negative side of the battery down. I don’t have photos of these two things, but I’ll share some similar types later on in this post.
Finally, since everything was unhooked, I pulled the original battery from the car and placed it on the ground. After that I grabbed the new battery and placed it next to the old one, just to make sure they match up in size and features. It looked like a perfect fit to me.
I knew the specs matched up, I wanted to make sure the physical size matched up as well. In the photo above, the original battery is an Exide and the replacement battery is a Duracell. I bought this Duracell for $130. Here’s a photo of the front of the new battery.
This is a Duracell 49 H8 car battery. It’s got 900 CCA and has 100 AH. That’s cold cranking amps and amp hours, if you aren’t in the business. It also weighs 58 pounds, which feels like a ton when you carry it.
After holding the wires out of the way with some bungee cords, I placed the new battery in its new home. I connected the terminals, the vent tube and then attempted to reattach the bracket that holds the battery down. This is where I had a bit of difficulty. Take a look at this bracket:
This bracket needs to get bolted down all the way at the bottom of the battery, on the negative side. To get my hand in this tiny area, I experienced some challenge. Eventually though, I managed to get lucky and I began turning the bolt into the hole. Once it was in somewhat, I finished with the socket. Here’s a photo of the narrow area. I circled the bolt hole in red.
I also want to mention that I unhooked one wire that led from the distribution panel to another cluster. In addition to that, I unhooked the two wire harness plastic ties that held the wires to the side of the car. All three are visible in this photo below.
I then reconnected the terminals, positive first.
I finished up by basically working in reverse. I reconnected everything that I disconnected. After that, I was finished.
The entire project took me about twenty minutes. Not challenging at all.
There’s some buzz on the internet that claims you need to have any freshly replaced battery in a BMW “registered” with the car. To do this, you either need to bring the car to the dealer or purchase a diagnostics tool yourself. All this registration does is tell the vehicle that a new battery is installed and that it should recognize that. To be honest, I’ve read a lot of competing feelings on this topic. I read a good article that was written by a BMW mechanic that said you actually don’t need to undertake this task and that the car will recognize the new battery after it drives for a while. Others say the world will end if you don’t.
When I first started the car after I installed the new battery, everything was fine. The only issue was that there were a few warning indicators lit in the instrument panel. The brake light wouldn’t shut off and the 4×4 indicator warning lamp was illuminated. When I drove the car, all that was needed was about 100 feet for all the warning lamps to turn off. This is just what I experienced, so things may be different for different folks.
I may go ahead and buy what’s called the “Carly Adapter & App.” Basically, you plug the adapter into the car’s computer and then, with its wireless capabilities, you read the diagnostics on your phone or tablet. Of course, you’ll need to download the app, but I think it’s worth it. I believe the cost of the adapter is around $80 and the app is something like $10. I’m not too sure about these prices.
This app is really cool. You can register a new battery, clear error codes and do some basic diagnostics. This can potentially save you tons of money and you might learn something about cars as well. This is in the future, so I’m still considering it.
I hope you enjoyed my post about replacing the battery in a BMW 3-Series. If you have any questions or comments, please leave them below. Thanks for reading!