Battery preconditioning enables faster and more efficient DC Fast Charging, particularly for folks in colder climates.
Unfortunately preconditioning is not available on pre-2024 ID vehicles.
Security engineer Fredrik Gustafsson (@jagheterfredrik on VWIDTalk.com) has developed an elegant solution to enable battery preconditioning (aka preheating) for VW ID vehicles that lack the feature (most 2021 – 2023 MEB vehicles and possibly some 2024 on software 3.x)
Fredrik’s solution uses a small CAN board to tell the ID gateway to activate the car’s internal heater and coolant pump to bring the battery up to optimal charging temperature. It does not bypass the car’s internal safety features, so the battery will not exceed the optimal temperature set by VW.
Check out the VWIDTalk Podcast on YouTube and wherever you get your podcasts ( Apple Podcasts, Spotify, Overdrive and more).
A transcript, cleaned up by AI and edited by a staffer, is below.
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Transcript:
Wes: This is what the app would look like. You get a lot of information about the car—the temperature, how much power it’s currently pulling, the state of charge—and there’s a big green button to start pre-heating the battery.
Wes: Okay, welcome back to the VWIDTalk Podcast. We’re your hosts, Wes and Jan. You can catch us on Spotify, OverDrive, Apple Music, or here on YouTube for a visual experience.
Jan: Today we have a special guest, Fredrik, who we like to call the ID.4 battery pre-heating inventor.
Wes: He has a solution to pre-heat the ID battery on MEB cars with a seemingly simple, yet technically sophisticated device. Fredrik, welcome.
Fredrik: Thanks, pleasure to be here.
Wes: So tell us, what did you build?
Fredrik: This is my first EV. Previously, I had a hybrid. In Sweden, during the winter, we often go north for skiing. When I was researching EVs, one major drawback of the ID.4 stood out: battery preconditioning and how poor charging is in winter. That got me thinking: I need to fix this.
I got my EV back in early March, so I haven’t experienced a full winter yet, but I wanted to be ready. I built a device that connects to your car and tells it, “Please preheat now,” using the car’s built-in battery preheating function. It’s not a separate heater—you’re leveraging the car’s existing hardware and software.
Jan: That’s clever.
Fredrik: Volkswagen cars come with a battery heater, necessary to bring the battery from sub-zero temperatures up to operational levels. All MEB models have it installed. While the car will automatically heat to around zero Celsius, my device lets you precondition the battery to a more optimal temperature before charging or driving in very cold conditions. This protects battery longevity and allows faster DC fast charging.
Wes: So it’s mostly useful for long trips and fast charging in cold weather, not everyday home charging.
Fredrik: Exactly. For home charging, the car handles battery heating safely on its own.
Jan: In Sweden, temperatures can drop as low as minus 20 Celsius. How often does that happen?
Fredrik: That’s worst-case for Stockholm. Further north can be colder, but skiing trips are usually between -10 and 0 Celsius, around 15 to 0 Fahrenheit.
Wes: I love the way you described this as a “man-in-the-middle” solution. You tap into the CAN bus, right?
Fredrik: Yes, I intercept the CAN bus wires with a device that communicates with the battery management system (BMS) to trigger preheating. My early prototypes involved reverse-engineering the BMS protocol to understand how the heater is controlled. One failed attempt was trying to turn on the heater manually without triggering the coolant pumps—the system needs coordinated activation.
Eventually, I realized I could trick the BMS using the standardized UDS protocol to send a “test battery heating circuit” command. This is a testing function that tells the system to activate the heater safely.
Jan: So you’re using the car’s existing systems without invasive modifications.
Fredrik: Exactly. I also looked at the OBD11 app, which allowed preconditioning but had limitations like needing to open the hood. My solution bypasses those limitations.
Wes: That’s brilliant. Can you walk us through your prototypes?
Fredrik: Sure. The first was a USB2CAN device connecting to the harness. My second prototype is a custom PCB with a buck converter, powering a microcontroller, and a button mounted via a 3D-printed holder. Pressing the button triggers preheating.
Jan: I see the ESP32 on top.
Fredrik: Yes, and the app communicates via Bluetooth. You just plug the device in, and it’s controllable from your phone.
Wes: That’s amazing. How about the UI?
Fredrik: The app shows battery temperature, current power draw, state of charge, and includes a big green preheat button. I’m still refining some data like charging potential, which requires more DC fast-charging sessions to calibrate.
Jan: And if someone wants this solution?
Fredrik: Version 1 is on my GitHub, using a USB-powered setup. Version 2 with the app is a work in progress. I’m considering open sourcing it or selling pre-assembled PCBs.
Wes: Is the device safe?
Fredrik: Yes. It communicates with the car to bring the battery up to testing temperature. The system has built-in failsafes, so it won’t overheat.
Jan: Do you have an engineering background?
Fredrik: Yes, but in cybersecurity, not automotive engineering. That background helped me understand vulnerabilities and protocols.
Wes: Any final thoughts?
Fredrik: I’d like companies to prioritize local network access for these functions instead of relying on cloud services. Users should be able to control battery heating locally.
Jan: Absolutely. Fredrik, this is an incredible solution.
Wes: Check Fredrik’s GitHub. We’re recording in September 2025, so by the time you see this, there may be updates. Please like and subscribe—we’re a volunteer community with no sponsors. Stay tuned for the next episode where we drive our car to 0% and see what happens. Thanks, Fredrik!
Fredrik: Thanks!
