How to change & register a car battery

How to change & register a car battery
Car batteries tend to fail when you least expect it, often in extreme weather conditions, after long periods of inactivity, or simply due to age.
While your first instinct might be to call a mechanic, changing a car battery is actually a task you can handle on your own with a bit of guidance. Just keep in mind there’s more to swapping out the old for the new – you’ll also need to register it, so your electrical systems function right.  
In this guide, we’ll walk you through the entire process of changing and registering a car battery. You’ll learn how to determine when your battery needs replacing, how to change it, and finally, how to register a new battery in different vehicle makes.  
Pro tip: If you're ready to replace and register your car battery, you can go straight to the step-by-step video where we show battery replacement and registration in action.  

When you need to change a car battery? 

A car battery typically lasts between three to five years, but several factors can shorten its lifespan – like extreme temperatures, frequent short trips, and leaving your lights on.
The most obvious sign that you’re dealing with a dead battery is when your engine simply won't turn over. However, there are a few other symptoms you can watch for before your car fails completely.
  • Slow engine crank: When your engine takes longer than usual to start, it often signals that your battery is losing its charge.
  • Dashboard warning lights: When your battery is weak, different car systems can stop working properly, too. Thus, various dashboard lights, like check engine light, battery charge warning, or other assist-related warnings might appear. 
  • Low battery fluid level: If your battery has removable caps, check the fluid level. Low levels can indicate your battery is nearing the end of its life. 
  • Swollen battery case: Extreme temperatures can cause the battery case to swell, which usually means it's time for replacement. 
  • Battery leaks: Corrosion around the battery terminals or visible leaks show that the battery is damaged and should be replaced immediately. 
Further reading: How to test a car battery 

How to change a car battery step by step

Changing a car battery is a classic DIY task, even for those who aren’t hardcore car enthusiasts. In fact, it only involves four simple steps:
1. Locate the battery
Most automotive batteries are found under the hood, tucked off to one side. However, some can be mounted in the trunk, under the backseat, or even in the wheel well.
If you're struggling to find your battery, check your owner's manual for its exact location.
2. Disconnect the terminals
Safety comes first here. Wear gloves and safety glasses to protect yourself from battery acid.
Always start by disconnecting the cable from the negative battery post to prevent any electrical shorts. any sparks or electrical issues. Then, disconnect the positive terminal.
Note: It's crucial to start with the negative terminal to avoid any sparks or electrical issues.
Be careful not to allow any metal objects to touch both battery posts simultaneously. Also, don't let your wrench touch the positive terminal and the body or fender at the same time.
3. Remove securing brackets
Remove any securing brackets or clamps that hold the battery in place. Lift the battery out of its tray carefully, as it can be quite heavy. Gloves will help protect you from any acid that might be on the battery.
4. Install the new battery
Before placing the new battery in, make sure it’s fully charged. Remove the red and black plastic covers from the ends of the battery posts.
Pro tip: Some drivers like adding anti-corrosion washers onto both battery posts and then treating the car's terminal ends with some anti-corrosion solution or coating them with a corrosion-resistant gel. 
Place the new battery in the battery tray and secure it with brackets or clamps. Reconnect the terminals – this time, start with the positive terminal first, followed by the negative terminal. Make sure all connections are tight and secure. 
Remember: Figuring out why your old battery gave up is key. Whether it's age, a leak, or a charging issue, you'll want to sort that out first to prevent similar issues with a new battery.
Now, after you change your car battery, that might just not be the end of the process.
For modern cars with start/stop system or intelligent battery sensors (IBS), a crucial step afterward is battery registration.

What is battery registration?

Car battery registration, also known as battery adaptation, is a programming procedure that informs your vehicle's electrical system that a fresh battery has been installed. 
It's crucial for modern cars equipped with advanced battery monitoring and start/stop systems, such as those found in Audi, Volkswagen, and BMW vehicles.

Why you need to register a car battery

When you replace a car battery, the vehicle's battery management system (BMS) needs to know the specifications of the new battery to manage its charging and discharging cycles properly. Without this data, the vehicle won't be able to adjust and charge the battery correctly, resulting in faster battery wear or electrical malfunctions.
But what if you’re replacing your old battery with an identical one?
You still need to register it. Your BMS needs to know the battery is new so it can reset and recalibrate its monitoring.

What happens if you don't register a new battery?

Skipping car battery registration can lead to several issues – let us paint a picture for you.
Charging problems
Your car might either undercharge or overcharge the battery. Undercharging leads to sulfation, where the battery plates degrade, while overcharging can cause overheating and the loss of vital battery electrolytes.
Either way, it's like pushing your battery on a swing – too little or too much, and things go sideways, cutting its lifespan.
Start/stop system malfunctions
More so, your car's start/stop system might not function properly without proper registration. This oversight can increase fuel usage, as the engine won't shut off as usual.
Electrical issues 
Finally, skipping registration can open Pandora's box of electrical issues. You might see a rainbow of warning lights on your dashboard, experience blown fuses, or face system failures. In some cases, your car might not start at all.

How to register a car battery with OBDeleven

For Volkswagen Group vehicles, like Volkswagen or Audi, you’ll need the OBDeleven NextGen device, the PRO VAG or the ULTIMATE VAG subscription, and the OBDeleven VAG mobile app.
Get OBDeleven for VAG
Plug the device into your car's OBD2 port and connect your smartphone via Bluetooth.
Then, go to the list of control units. 
Here’s where the steps get different for VAG vehicles with the KWP2000 protocol and VAG models with the UDS protocol. We’ll refer to them as older VAG models and newer VAG models for clarity reasons.  
For older VAG models
Scroll down to find the control unit called “Battery Regulation,” click on it, and select "Long Adaptation." Enter channel number 4 and hit “Done.” 
Tap on the "Value” field to input your battery information. Start with the first three digits for battery capacity, followed by a space.
Then, add the three symbols for the manufacturer code, another space, and the 10-digit serial number.
You can find these codes on a white sticker on the battery. If there’s no sticker, simply enter “UNK” for the manufacturer and change the last digit of the serial number. Then, confirm the changes.
If your new battery is different from the old one, take a few extra steps:
Go back to the “Battery Regulation” control unit and select “Long Coding.” Update the battery type to the correct one, then slide right to confirm.
For newer VAG models
For these newer models, the process is more straightforward. Once connected, find the control unit named “Gateway,” click on it, and choose "Adaptation."
Here, select "Battery adaptation" and fill in all fields with battery capacity, manufacturer, serial number (if you don't know, simply change the last digit), and battery technology. Slide right, and that's it.
For BMW vehicles
Things are even simpler for BMW vehicles. You'll need the OBDeleven NextGen device and the OBDeleven app for this.
If your new battery type and capacity differs from the old one, navigate to "Apps," find the "Battery Type and Capacity" option, and select your new battery type. Skip this part if the type and capacity are the same.
Then, open the "12V Battery Registration" app, select the “RESET” option, slide, and you're set.
Check out our step-by-step video tutorial below for a more detailed visual walkthrough. It will guide you through battery replacement and registration so you can feel even more confident before doing it on your own.
Disclaimer: Advice, how-to guides, and car care tips on our blog are intended as helpful resources for general maintenance and repairs. While we strive for accuracy, the information is provided to the best of our knowledge and should be used at your own discretion and risk.

Always refer to your vehicle's owner's manual or consult a certified mechanic for specific repair details and safety procedures.