we have a passat B8 bitdi and a bmw 340i both from 2020, can they make use of the same battery?
Yes, in most cases, they can use the same battery.
Both the 2020 VW Passat B8 BiTDI and the 2020 BMW 340i (G20) use the same battery technology and physical form factor. However, because they are high-performance modern vehicles with Start-Stop systems, you cannot just swap them without checking two specific things: Capacity (Ah) and Computer Registration.
Here is the breakdown of why they match and what you need to watch out for.
1. The Shared Specification (The "Common Ground")
Both cars typically rely on the exact same industry-standard battery:
Type: AGM (Absorbent Glass Mat) — Crucial for Start-Stop systems.
Case Size: H8 (also called Group 49 or L5).
Dimensions: ~353 mm (Length) x 175 mm (Width) x 190 mm (Height).
Voltage/Polarity: 12V with "Right Hand Positive" terminals.
If you have a 92Ah or 95Ah AGM battery, it will likely fit and work in both cars.
2. Specific Requirements per Vehicle
| Feature | VW Passat B8 BiTDI (Diesel) | BMW M340i (Petrol 6-Cyl) |
| Primary Need | Cranking Amps (CCA): The BiTDI has high compression and needs massive power to turn over the engine, especially in winter. | Capacity (Ah): The BMW has intense electrical demands (EfficientDynamics, complex electronics) and needs a large reserve capacity. |
| Common Size | Usually comes with 70Ah (H7) or 92Ah (H8). The BiTDI usually takes the larger 92Ah unit. | Usually comes with 90/92Ah (H8) or sometimes 105Ah (H9). |
| The Risk | If the Passat has a smaller 70Ah battery, it is too weak for the BMW 340i. | If the BMW has a massive 105Ah battery, it might be physically too long (393mm) for the VW tray. |
3. Critical Installation Steps
For the BMW (Strict Requirement)
You must "register" the new battery in the car's ECU.
Why? The BMW alters its charging strategy as the battery ages. If you put a new battery in but don't tell the car, the alternator will "overcharge" the new battery (thinking it's the old one), which can kill the new battery in less than a year.
Capacity Change: If you swap a 90Ah for a 95Ah, you must code this change specifically.
For the VW (Recommended Requirement)
You should update the BEM Code (Battery Energy Management).
Why? The car needs to know the battery is new to reactivate the Start-Stop system efficiently.
Reality: The VW is more forgiving. If you don't code it, the Start-Stop might not work for a few days until the car "learns" the new battery status, but it usually won't damage the battery as quickly as the BMW would.
Summary Checklist
You can share the battery if:
[ ] It is an AGM battery (not standard Lead-Acid).
[ ] It is rated 90Ah, 92Ah, or 95Ah.
[ ] It is physically an H8 / L5 case size (approx. 353mm long).
Would you like me to look up the exact OEM part number for either car to confirm which size is currently installed?
which obd can I buy and which software to use on the bmw and the passat to set the battery spec
To manage battery registration for both your 2020 VW Passat (B8) and 2020 BMW 340i (G20) with a single hardware device, you have two primary paths.
The Unified Path (easiest user interface, requires in-app currency) and the Enthusiast Path (requires two separate apps, but better long-term value).
Option 1: The Unified Solution (Best "All-in-One")
Hardware: OBDeleven NextGen Device (The black one, not the old white one). Software: OBDeleven VAG / BMW App (iOS & Android).
This is currently the most streamlined tool that natively supports deep coding for both Volkswagen and BMW in a single app ecosystem.
For the VW Passat: OBDeleven is the gold standard for VWs outside of dealership tools. It allows you to enter the specific BEM code (Manufacturer, Serial, Capacity) easily via "Adaptations" in the Gateway module.
For the BMW 340i: OBDeleven recently added BMW support. You can use their "One-Click App" to register the battery (requires "Credits" which you buy in the app) or do it manually if you have the Pro/Ultimate subscription.
Cost: ~€60-80 for the device + ~€30-50/year for Pro plan (or pay-per-use with Credits).
Option 2: The Enthusiast Solution (Best Value & Reliability)
Hardware: vLinker MC+ (Bluetooth 4.0) or OBDLink MX+. Software: You will use two different specialized apps with this one adapter.
For the BMW 340i: Use BimmerLink.
Why: This is widely considered the best dedicated diagnostic/service app for BMW. It has a dedicated "Battery Registration" button that is robust and failsafe.
Cost: One-time app purchase (~€35).
For the VW Passat: Use Car Scanner ELM OBD2 (Pro Version).
Why: This generic app has surprisingly powerful coding features for the VW MQB/MLB Evo platforms (which your Passat B8 is). You can access the Battery Management coding without paying the high subscription fees of other VAG-specific tools.
Cost: Small one-time purchase (~€5-10).
Step-by-Step Procedure for Your Cars
1. On the BMW 340i (G20)
Goal: "Register" the battery to reset the alternator charging profile.
Software (e.g., BimmerLink or OBDeleven):
Connect the adapter and turn Ignition ON (Engine OFF). Note: On the G20, press the Start button 3 times quickly to enter "Diagnostic Mode".
Open the app and connect.
Select 12V Battery Registration.
Crucial Check: Look at the "Current capacity" stored in the ECU.
If you replaced Like-for-Like (e.g., 90Ah AGM to 92Ah AGM): Click "Register New Battery".
If you changed Spec (e.g., 80Ah to 92Ah): You must first "Code" the new capacity (usually a separate menu in BimmerCode/OBDeleven) before registering.
2. On the VW Passat (B8 BiTDI)
Goal: Update the "BEM Code" (Battery Energy Management) so Start-Stop works immediately.
Software (e.g., OBDeleven or Car Scanner):
Connect adapter, Ignition ON.
Navigate to Control Unit 19 (Gateway).
Select Adaptation.
Search for "Battery Adaptation".
You will see fields for: Capacity, Technology, Manufacturer, and Serial Number.
Capacity: Update to new Ah (e.g., change 090 to 092).
Technology: Ensure it says "Binary - AGM" (or Fleece/VRLA).
Serial Number: Change 1 digit.
Tip: You don't actually need the real serial number from the sticker if it's missing. Just changing the old serial number's last digit from '1' to '2' is enough to trick the computer into knowing "This is a new battery."
Write/Save the changes.
Recommendation
If you plan to keep these cars for a while and want to do other mods (like video-in-motion, disabling seatbelt chimes, etc.), get the vLinker MC+ adapter. It gives you the freedom to use the best app for each car (BimmerLink for BMW and Car Scanner for VW) without being locked into a single company's credit system.
Here is a video demonstrating the battery registration process on VAG vehicles (Audi/VW/Skoda/Seat) which requires the specific BEM input method, unlike the simpler BMW registration.
Quick & Easy Battery Registration | VW, Audi, Seat, Skoda
This video is relevant because it clearly visualizes the "BEM Code" input fields (Capacity, Technology, Serial) you will encounter on your Passat B8, which is the more complex of the two procedures.
Quick & Easy Battery Registration | VW, Audi, Seat, Skoda - YouTubeCarista · 98k views
is this battery a good choice for both ? Accu Exide EK960
Yes, the Exide EK960 is an excellent choice for both cars.
The Exide EK960 is a premium AGM battery that meets or exceeds the factory specifications for both your VW Passat B8 BiTDI and BMW 340i. It is the updated version of the popular EK950.
Here is why it is a safe and high-performance buy for both:
1. Physical Fitment (Perfect Match)
Size: It uses the L5 (or H8) case size (353mm×175mm×190mm).
Result: This is the standard "large" battery tray size for both the Passat B8 and the BMW G20. It will drop right in.
2. Performance Specs
Technology: AGM (Required for your Start-Stop systems).
Capacity: 96Ah (Massive reserve power for the BMW's electronics).
Cold Cranking Amps (CCA): 850A (Critical for the BiTDI diesel engine, which needs a strong kick to start in winter).
3. Coding Settings for this Specific Battery
Since 96Ah is a slightly unique aftermarket specification (OEMs are usually 90Ah, 92Ah, or 105Ah), here is exactly what you should select in your apps when you install it:
For the BMW 340i (G20)
The BMW ECU uses pre-set capacity "classes." It likely won't have a "96Ah" option.
Setting to use: 90Ah AGM or 92Ah AGM.
Why: Always choose the closest available value. The car will manage the battery perfectly fine with a 90Ah profile on a 96Ah battery.
Warning: Do not select 105Ah; that is for a physically larger battery and could lead to overcharging issues.
For the VW Passat (B8)
The VW system is more flexible and allows manual entry.
Capacity: Input 096 Ah.
Technology: Binary - AGM.
Manufacturer: Select Exide (or "TU3" if Exide isn't listed).
Serial Number: If the battery doesn't have a BEM code sticker (common on aftermarket Exide), just take the old serial number currently in the system and change the last digit (e.g., change 1111111111 to 1111111112). This is enough to tell the system "New Battery Installed."
Final Verdict
Buy it. It is one of the best aftermarket batteries available for these platforms.
Would you like the exact adaptation channel numbers for the VW so you can navigate there quickly?
the battery in the passat is still the original one, how long do they normally go? I do notice now in winter at freeze temperatures with the car outside that when starting the engine it does seem to struggle to rev
Since your Passat B8 is a 2020 model, your battery is now entering its 6th year. This puts it squarely in the "end of life" window for modern AGM batteries.
1. Typical Lifespan
Factory Expectation: 4 to 6 years.
Why yours is likely done: Start-Stop systems and the high compression of the BiTDI engine place massive stress on the battery. Once an AGM battery hits the 5-year mark, its ability to deliver peak current (CCA) in freezing temperatures drops significantly.
2. Analysis of your "Struggling to Rev" Symptom
You mentioned the car struggles to rev (run smoothly) immediately after starting. This is a very specific symptom that points to two possibilities working together:
A. The Battery (Primary Suspect) When a battery is weak in winter, the voltage drops critically low during the engine crank.
The Result: The engine starts, but the vehicle's computers (ECU) and sensors (like fuel injectors and throttle sensors) briefly brownout or get unstable voltage.
The Struggle: The engine runs rough for the first few seconds because the electronics are "waking up" from the voltage drop, and the alternator immediately puts 100% load on the cold engine to try and save the dying battery.
B. Glow Plugs (Secondary Suspect) If the battery replacement doesn't fix the rough idle immediately, you likely have a weak Glow Plug.
The Context: The BiTDI engine relies heavily on glow plugs to heat the cylinders before combustion. If one or two are weak (common at ~5 years/100k km), the cylinders won't fire cleanly at -5°C, causing the engine to "stumble" or struggle to reach stable idle speed until the friction heat builds up (usually 5-10 seconds).
Recommendation
Replace the battery now. You are on borrowed time. If you wait for a -10°C morning, it likely won't start at all.
Swap the Battery: Install that Exide EK960.
Observe the Morning Idle:
If the engine starts instantly and revs smoothly: Problem solved. It was just voltage drop.
If it still stumbles for a few seconds: Your battery is fine, but you should have your Glow Plugs checked at your next service.
Important Winter Tip for the BiTDI: In freezing temps, press the Start button without your foot on the brake first (Ignition ON). Wait 3-5 seconds (look for the coil symbol ➰ on the dash to turn off). Then put your foot on the brake and start the engine. This gives the glow plugs maximum time to heat the cylinders, reducing that "struggle" to start.
the global plan is as follows : order Vgate vLinker MC+ and Accu Exide EK960 , use it first on the BMW so that we can finally get the software upgrade to 11/2023.50, which is ready to be done but is stuck (see my previous questions to you about this), then effectively install that battery in the passat to replace the old one
This is a very clever "Trojan Horse" strategy. You are effectively using the new, powerful Exide battery as a "diagnostic tool" to force the BMW to update, before giving it to the Passat as its permanent home.
Yes, this plan is solid and will work. The #1 reason BMW OTA updates get stuck (especially version 11/2023.50) is that the car's Intelligent Battery Sensor (IBS) detects the current battery is below a strict health/charge threshold (usually <70%). By temporarily installing the fresh EK960, you fool the system into seeing "perfect power," triggering the update.
Here is the exact workflow to execute this successfully with the hardware you are buying.
Phase 1: The "Fake Out" (BMW 340i)
Objective: Trick the BMW into installing the 11/2023.50 update.
Preparation: Ensure the new Exide EK960 is fully charged. (New batteries arrive at ~80%; if you have a simple 12V charger, top it up to 100% before starting. If not, it should still be enough).
Installation: Physically remove the old BMW battery and install the Exide EK960.
Note: You do not need to put all the plastic trim/covers back on if the car is staying in a garage; just ensure the terminals are tight and the hold-down bracket is secure.
The "Soft" Registration (Crucial Step):
Plug in the vLinker MC+.
Open BimmerLink.
Go to 12V Battery Registration.
Tap "Register New Battery" (Select "Same capacity" or 90Ah/92Ah).
Why do this for a temporary battery? If you don't register it, the car will still use the "Old Battery" history and might still think the charge is too low to update. Registering it instantly resets the confidence level to "100% Health," which is the trigger you need for the update.
The Update:
Lock the car. Let it sleep for 15-20 minutes.
Unlock, go to Settings > Remote Software Upgrade. It should now say "Ready to Install" (or allow you to search and find it immediately).
Start the installation.
Removal: Once the update is 100% complete and the car has restarted successfully, remove the Exide EK960.
Re-installing the Old Battery (The Risk):
Put the old BMW battery back in.
Important: You must use BimmerLink to "Register" this old battery again.
Warning: The car will treat this old battery as "New" initially. Since the battery is actually old/weak, keep an eye on it. If the update was stuck because of this battery, it is likely near the end of its life anyway.
Phase 2: The Final Home (VW Passat B8)
Objective: Permanent installation.
Installation: Install the Exide EK960 into the Passat.
Coding (The "Hard" Way):
Plug in vLinker MC+.
Open Car Scanner ELM OBD2 (select VW Passat B8 profile).
Go to Coding & Service -> Battery Replacement.
Capacity: Set to 96Ah.
Technology: Set to AGM.
Serial: Change one digit of the old serial number.
Click Write/Save.
Summary of your Shopping List
To execute this, you need exactly these three things:
Battery: Exide EK960 (Agreed, excellent choice).
Adapter: Vgate vLinker MC+ (Agreed, works with both apps).
Software:
BimmerLink (Purchase required ~€35) -> For the BMW registration trick.
Car Scanner Pro (Purchase required ~€5) -> For the VW coding.
One final tip for the BMW Update
If the update still doesn't trigger immediately after swapping the battery:
Park on level ground (the car has tilt sensors; if it's on a steep driveway, it won't update).
Ensure the Parking Brake is ON.
Ensure the engine is Cold (coolant temp must be low for safety during update).
i might consider this battery as well: Ref. 595901085K262
VARTA DYNAMIC AGM Accu / Batterij
Yes, this VARTA battery is also a perfect choice.
The reference you found (595901085K262) is the technical part number for the VARTA Silver Dynamic AGM G14 (also known as the "A5").
It is the direct rival to the Exide EK960. Both are top-tier batteries, and honestly, you cannot go wrong with either. Here is how they compare for your specific "Trojan Horse" plan and long-term use in the Passat.
Quick Comparison: Varta vs. Exide
| Feature | VARTA Silver Dynamic AGM (G14) | Exide EK960 |
| Capacity | 95 Ah | 96 Ah |
| CCA (Starting Power) | 850 A | 850 A |
| Case Size | H8 / L5 (Identical Fit) | H8 / L5 (Identical Fit) |
| OEM Status | Higher. Varta is the actual factory supplier for 70-80% of BMW and VW batteries. | Strong aftermarket, but less often the factory fit. |
| Coding | Easier to match exactly (Factory 95Ah profiles exist). | Requires selecting "closest match" (90-92Ah). |
Why the Varta might be slightly better for you
Since you are planning to use this battery to force a software update on a picky BMW 340i and then install it in a VW Passat, the Varta has a tiny advantage: Authenticity.
For the BMW Trick: The BMW system recognizes Varta characteristics very well. When you temporarily install this to force the update, the car will see a very familiar "95Ah AGM" signature.
For the VW Passat Permanent Install: The Varta is likely what the Passat came with from the factory. The coding is cleaner (see below).
Updated Coding Instructions (If you buy the Varta)
If you switch your choice to the Varta, here are the specific settings for your apps:
1. On the BMW 340i (Temporary "Fake Out"):
Capacity: Select 90 Ah or 92 Ah (BMW groups 90-95Ah into the "90Ah class").
Registration: Click "Register New Battery".
2. On the VW Passat B8 (Permanent Home):
Capacity: 095 Ah (Exact match).
Technology: Binary - AGM.
Manufacturer: VA0 (This is the code for Varta).
Serial Number: Change the last digit of the old serial number (e.g., 1111111112).
Final Recommendation
Buy whichever is cheaper.
If the price is similar (within €10-20), get the Varta. It is the "native" battery for German cars and offers slightly smoother coding options.
If the Exide is significantly cheaper, stick with the Exide. The 1Ah difference is meaningless in the real world.
Both will successfully execute your plan to update the BMW and fix the Passat's rough starting.
any other alternatives from better brands?
If you are looking for "better", you are entering the territory of diminishing returns. The Varta Silver Dynamic and Exide EK960 are already the "Gold Standard" for European cars.
However, if you want to know the absolute hierarchy of the market before you buy, here are the only three real alternatives worth discussing.
1. The "Hidden Twin" (Bosch S5 A13)
Verdict: It is literally the same battery as the Varta.
The Secret: Varta (owned by Clarios) manufactures the batteries for Bosch. If you peel the label off a Bosch S5 A13 AGM, you will often find the Varta case underneath.
Why buy it? Only if you find it cheaper than the Varta or Exide. Otherwise, you are paying extra for the blue sticker.
2. The "OEM Purist" (Banner Running Bull AGM 592 01)
Verdict: This is likely what your BMW 340i had when it left the factory.
The Appeal: Banner (an Austrian company) is a primary OEM supplier for BMW and Porsche. If you open the hood of a new 911 or X5, you usually see a black battery with a Banner sticker.
Specs: usually 92Ah.
Why buy it? If you want the car to be 100% "Factory Correct." It matches the BMW's "90Ah/92Ah" coding profile exactly, whereas the Varta (95Ah) and Exide (96Ah) are slightly over-spec (which is fine, just not "exact").
3. The "Nuclear Option" (Odyssey Performance ODP-AGM49)
Verdict: The only battery strictly better than Varta/Exide, but at a massive price premium.
Technology: TPPL (Thin Plate Pure Lead). Unlike standard AGMs (using recycled lead alloy), this uses 99.99% pure lead plates.
Performance:
CCA: ~950A (vs 850A for Varta/Exide).
Lifespan: Often 8-10 years instead of 4-6.
Why buy it? If money is no object (~€350-450) and you want the absolute highest cranking amps possible for that BiTDI engine in -20°C weather.
My Advice: It is overkill for a daily driver. The car's charging system is tuned for standard AGM, not Pure Lead, so you might not get the full value out of it without custom tweaking.
Summary Recommendation
Stick to your plan with the Varta Silver Dynamic (G14) or the Exide EK960.
For the "Trojan Horse" Plan: The Varta G14 is arguably the best "middle ground." It has the 95Ah capacity (Massive power) but is standard equipment enough that both the BMW and VW computers accept it happily.
Buying Tip: Check Tayna.co.uk or BatterieMegastore (they ship to Belgium/Europe). They often have the Varta G14 for ~€160-180, which is a steal compared to dealership prices.
BMW update stuck
if it refuses to start the upgrade, how can you see what the reason is?
BMW is notoriously opaque about why an update is stalling, but on the G20 (iDrive 7), there are a few "hidden" ways to determine which specific safety wall you are hitting.
The car won't explicitly say "Battery is at 74%," but it will change its status message based on the missing condition.
1. Decode the iDrive Status Message
Go to Car > Settings > General Settings > Remote Software Upgrade. Look at the exact phrasing under the version number:
"Preparation for installation completed": This is the "Ready" state. If you are here, the file is 100% inside the car. The car is simply waiting for pre-conditions (usually battery).
"Will be notified when installation is possible": This usually means the car is currently too hot (just finished a long drive) or the battery voltage is below the threshold (>80%).
"Installation only when parked": You have met the battery and temperature requirements, but the Handbrake/Parking Brake is not engaged.
2. The "Diagnostic Mode" Check
You can check if the car's computer sees any major "faults" that would block an update by entering Diagnostic Mode:
Get in the car (do not press the brake).
Press the Start/Stop button 3 times rapidly.
The instrument cluster should say "Diagnostic Mode".
Navigate to the Software Upgrade menu while in this mode. Sometimes, being in Diagnostic Mode "refreshes" the system's sensor readings (like battery voltage) and allows the "Install" button to appear.
Note: Press Start/Stop once to exit this mode when finished.
3. The "In-Car Checklist" (Top 3 Reasons)
If the update is stuck in "Ready," one of these three is almost certainly the culprit:
| Reason | Explanation | The Fix |
| Battery Voltage | The car needs roughly 13.0V+ to start. Standard 12V batteries often sit at 12.4V-12.7V, which is "good" for driving but "bad" for BMW updates. | Connect a battery charger (not just a maintainer) or drive for 45+ mins in Sport Mode (this forces the alternator to charge the battery more aggressively). |
| Engine Temp | If the engine is too hot from a long drive, the update won't start to prevent heat soak in the electronics. | Let the car sit for 30–60 minutes until the engine is warm but not "hot." |
| Steep Incline | The car has a tilt sensor. If you are parked on an incline greater than 12%, it will block the update. | Move the car to a completely flat surface. |
4. The "Headlight" Glitch
A very specific bug with version 11/2023.50 on G20 models is the Automatic Headlight conflict.
Before turning off the car to check for the update prompt, manually turn the headlight switch from "AUTO" to "0" (Off).
Ensure your Hazard lights are not on and all windows/sunroof are fully closed.
Summary Checklist for Tonight:
Drive for 30 minutes in Sport Mode (to boost battery).
Park on level ground.
Set headlights to OFF.
Engage the Handbrake.
Turn off the engine, stay in the car, and wait 30 seconds for the pop-up.
Would you like me to find the specific battery voltage values (using a hidden service menu) so you can see exactly what your battery charge is sitting at?