Are you getting a message on your BMW dashboard to recharge the battery, meaning that you need to replace it? Do you want to know how to replace the car battery without losing data? You’ve come to the right place, for we have researched this question, and we have the answer for you.
Connect a jumper battery to the jumper terminals under the hood. Remove the old battery and put in the new battery. Disconnect the jumper battery, and you’re good to go.
Let’s talk more about the details of replacing the battery in your BMW in the sections below.
How do I know if my BMW battery needs to be replaced?
The car battery of your BMW—like all other car batteries—will not last forever.
Your car needs the electrical energy provided by the car battery to provide power to the starter motor. The starter motor, on the other hand, is responsible for cranking the engine's flywheel. The flywheel rotation initializes the movement of the engine's cylinders.
This brings us to the first and most common sign that you need to replace the battery—your car is having a hard time starting. The alternator charges the car battery whenever you drive your car. However, the capacity of the battery naturally drops as it ages.
Dashboard Warning Lights
A modern BMW has a lot of sensors that feed information to the computer or the ECU (Engine Control Unit). The ECU will then interpret the different data that it receives.
A drop in the electrical energy that the ECU receives can trigger the "Check Engine" light on your dashboard. If there is a specific module that is more sensitive to the drop in electrical supply, then you could see the warning light for that module on the dashboard.
Most modern BMW models will display a message on the dashboard to let you know about the battery issue. You will receive a message to charge your car battery even though you drive your car daily.
The alternator is responsible for charging the battery while you drive. This is to recover the charge that the battery lost to start the engine.
Poor Performance During Cold Months
Cold days can throw a wrench into the performance of a car battery. However, the car battery is not the only component with sluggish performance during winter. Even the internal combustion engine’s performance will suffer.
During the winter months, the engine oil will become thicker, making it harder to lubricate the engine parts. The thick oil will also make it harder for the parts to move freely.
Condensation in the engine parts will freeze at cold temperatures, and the combustion process will become more sluggish than normal. This situation with the engine means that the starter motor will need extra juice from the battery to start the engine. Fortunately, the first few strokes of the engine cylinders are enough to produce enough heat to warm up the engine.
However, the larger demand for electrical energy is not the only reason why batteries become less effective in cold weather. Cold temperatures increase the resistance in the battery electrolytes. Resistance makes it harder for electrical energy to flow.
Thus, the increase in resistance leads to a less effective battery.
However, battery manufacturers compensate for the drop in temperature when they design their batteries. Therefore, the drop in the battery performance during winter should not be so bad that the battery cannot start your BMW anymore.
If your battery cannot start your BMW in winter, then it is a good sign that it is time to replace the battery.
How to replace the battery of your BMW without programming?
Replacing the car battery of a modern BMW vehicle will lose data that the ECU uses to perform some of its functions behind the scenes. However, programming your BMW after replacing the battery requires a trip to a dealer unless you have the equipment for reprogramming.
Here are the complete steps to replace the battery on your BMW to avoid reprogramming it:
Preparing Your BMW
- Park your BMW in a well-lit area.
- Activate the parking brakes.
- Set the transmission to "Park(P)."
- Turn off the engine.
Connecting A Secondary Power Supply
- Get a fully charged jumpstart battery or a jumpstart power supply.
- Open the engine bay of your BMW.
- Look for the bright red rubber cap with a large “plus” sign in the middle. The rubber cap should be close to the engine bay sidewall. It should be near the upper layer of the engine bay.
- Open the positive terminal on your BMW.
- Connect the positive cable from the jumpstart power supply to the positive terminal.
- Next, look for the negative terminal. It should be close to where you found the positive terminal. However, unlike the positive terminal, the negative terminal doesn’t have an enclosure. It would look like a nut and bolt that is sticking out of the engine bay.
- Connect the negative cable from the jumpstart power supply to the negative terminal.
- If the jumpstart power supply has a power button, turn it on.
Taking Out The Old Battery
Removing The Panel
- Position the power supply so that it will not easily slide off.
- Open the trunk of your BMW.
- The BMW battery is typically in the trunk, on the rear-right side. Locate the locks keeping the panel in place. You can use plastic trim removers to prevent damage to the panel carpet.
- Remove the panel cover and set it aside.
Removing The Brackets
- Remove the bracket that holds the battery down by loosening the bolts that keep it in place.
- Loosen the long bolt that secures the bracket that prevents the battery from moving from side to side.
- If your battery has a distributor or junction box on the positive terminal, look for two clips that hold it in place. Loosen the two clips from the sides of the battery.
Disconnecting The Cables
- Disconnect the negative terminal from the battery by removing the nut. Be mindful that when you’re disconnecting the wires from your battery, you should always disconnect the negative terminal first.
- Be careful in disconnecting the negative terminal. Make sure that it doesn’t touch any of the car's metal parts.
- If you have a battery terminal cap, install one on the negative terminal since it is usually bare, unlike the positive terminal.
- In some BMW models, there is a cable with a blue connector coming from the wire mesh of the negative terminal wire and going to the positive terminal’s distributor. Disconnect that from the positive terminal.
- Next, check if you see a red cable with a black connector on the same distributor. If you do, disconnect that cable too.
- Loosen the nut that keeps the positive terminal in place. Remove the positive terminal and set it aside. Make sure that the two terminals never get in contact with each other.
Removing The Vent
- Check the sides of the battery for a vent hose. If you find one, disconnect it from the battery. The vent hose redirects any gas byproduct to the BMW's exterior.
- If you use a replacement battery from BMW, you will get one with a vent hole for the vent hose.
- Lift the old battery out of your trunk and set it aside.
Installing The Replacement Battery
- Lift the replacement battery into the trunk cavity. The vent hole of the new battery should be in the direction of the engine.
- Reconnect the vent hose to the side of the battery.
Connecting The Replacement Battery
Reverse the installation to connect the new BMW battery. There are two things that you need to take note of when you’re putting everything back.
- First, connect the positive terminal and the cables that go to the distributor of the positive terminal before you connect the negative terminal.
- Second, don’t forget to disconnect the jumpstart power supply before you try to start your BMW.
BMW Won’t Start After Battery Replacement
In some BMW models, the negative battery line has sensors that tell the ECU about the battery's status.
If you’re replacing a totally dead battery, the ECU’s last memory of the battery is that it is already dead. When you put in the new battery, it will remember the state of the last battery, preventing your BMW from starting.
To start your BMW, you need to bypass the sensor or bring your BMW to a dealer to register the new battery.
To bypass the sensors, look for the wire with a blue connector. You will find this wire on the same wire mesh as the wire for the negative terminal. Disconnect the blue connector and start your car.
Provide a temporary power supply that will keep the data of the ECU alive while you replace an old battery. This will allow you to replace the battery without losing data.
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