Everything You Need to Know About Resetting Your Car’s Battery Management System
If you own an electric vehicle (EV) or a newer gas-powered car, your vehicle likely has a complex battery management system (BMS) that carefully monitors the battery’s state of charge, health, temperature, and other key parameters. The BMS is critical for optimizing battery performance and longevity. However, sometimes the BMS can malfunction or get out of sync, requiring a reset to restore proper operation.
In this comprehensive guide, we’ll cover everything you need to know about automotive BMS resets – what they are, when you need one, how to perform a reset, and more. Whether you’re an EV owner, a mechanic, or just curious about this increasingly important automotive technology, read on to become an expert on BMS resets and take the best possible care of your vehicle’s battery.
What is a Battery Management System (BMS)?
Before diving into BMS resets, it’s important to understand what the battery management system does and how it works. Put simply, a BMS is an electronic system that monitors and manages a rechargeable battery or battery pack. In automotive applications, the BMS is responsible for keeping the large, high-voltage battery within safe operating conditions to deliver optimal performance and lifespan.
Some key functions of an automotive BMS include:
- Monitoring individual cell and overall pack voltage, current, and temperature in real-time to prevent overcharging, over-discharging, and overheating
- Estimating battery state of charge (SoC) – the amount of charge left compared to a full charge – to accurately calculate remaining driving range…
- Estimating battery state of health (SoH) – the condition of the battery compared to when it was new – to predict when the battery will need to be replaced
- Balancing the charge of individual cells in the battery pack to maintain equal voltage levels and maximize usable capacity
- Controlling contactors to connect or disconnect the battery from the rest of the vehicle’s electrical system as needed
- Communicating battery data to other vehicle systems and diagnostic tools
Modern automotive BMS solutions leverage precision sensors, powerful processors, and sophisticated algorithms to optimize battery utilization and health. The quality and capability of the BMS directly impacts an EV’s range, performance, and value.
Signs You May Need to Reset Your BMS
Normally, the BMS works quietly in the background and doesn’t require any special attention. However, there are some situations where the BMS can start acting up and may need to be reset to factory settings. Some common signs include:
1. Battery Drains Unusually Quickly
One of the most obvious symptoms of a faulty BMS is if your vehicle’s battery depletes much faster than normal, even when your driving habits haven’t changed. This could indicate the BMS is allowing the battery to be discharged beyond its normal limits.
2. Battery Overheats
A properly functioning BMS should prevent the battery from getting too hot by regulating charging and discharging currents. Battery overheating can not only degrade the battery faster but also poses a safety risk. If you notice your battery temperature gauge climbing into the red zone, a misbehaving BMS could be to blame.
3. Inconsistent or Inaccurate Battery Gauge
Does your battery charge level gauge seem to jump around erratically or get stuck, even though the battery is charging normally? This points to a glitch in the BMS’s ability to measure state of charge. Resetting the BMS may help it take a fresh reading and accurately track SoC again.
4. Frequent False Battery Warning Messages
Modern EVs have a slew of battery-related warning lights and messages to alert the driver of any potential issues. However,… a malfunctioning BMS can trigger these warnings even when there isn’t actually a problem, due to faulty sensor data. If you’re getting bombarded with error messages that a mechanic can’t diagnose, the BMS likely needs a reset.
5. Reduced Driving Range
If your EV isn’t going as far on a charge as it used to, this could be due to the BMS improperly managing the battery and not making the full capacity available. Resetting the BMS may help restore some of the lost range, although an old battery will still have reduced range compared to when it was new.
When and Why to Reset the BMS
In general, you should only reset your vehicle’s BMS if you’re experiencing one of the above symptoms or a mechanic recommends it. Resetting the BMS wipes out all of the learned battery data and restores the system to its factory default settings.
There are a few main situations where a BMS reset can be helpful:
1. Fixing BMS Software Glitches
Just like any computer system, the BMS can sometimes experience software bugs that cause it to malfunction or crash. Resetting the BMS is the equivalent of rebooting a computer – it clears out any corrupted data and gives the system a fresh start.
2. Recalibrating Battery Measurements
Over time, the BMS can start to drift in its ability to accurately estimate battery state of charge and other parameters. This is because the battery’s actual capacity slowly declines as it ages, while the BMS may still be assuming the original capacity values. Resetting the BMS allows it to relearn the battery’s true capabilities and give more precise range estimates.
3. After Replacing the Battery or BMS Components
If you’ve had your vehicle’s battery or BMS components replaced, a reset is usually necessary to clear the old component data and adapt to any changes in the new parts. This is especially important if the new battery has a different capacity or chemistry than the original.
4. After a Long Period of Storage…
EVs that have been left parked for many months can sometimes develop BMS issues due to the battery being allowed to drain extremely low. This is because the BMS needs a small amount of power to maintain its memory, and if this is lost, it may get confused when the vehicle is used again. Resetting the BMS can often resolve any odd behavior caused by long-term storage.
How to Reset Your Vehicle’s BMS
The exact steps to reset a BMS vary depending on the specific vehicle make and model, so it’s always best to consult your owner’s manual or a dealer for the proper procedure. However, the general process usually goes something like this:
- Fully charge the vehicle’s high-voltage battery pack using a Level 2 charger. This ensures the BMS has a good baseline to work from after the reset.
- Power down the vehicle completely. Make sure everything is turned off, including the headlights, infotainment system, climate control, etc. Some vehicles may have a special power down sequence for the high-voltage system.
- Disconnect the 12V accessory battery. Locate the standard 12V battery (usually under the hood) and disconnect the negative terminal. This cuts power to the BMS and clears its memory.
- Wait at least 15 minutes. This gives any residual power in the system time to dissipate.
- While waiting, press and hold the brake pedal for at least 30 seconds. Some vehicles have a manual reset procedure that involves holding the brakes to drain any remaining power in the actuators.
- Reconnect the 12V battery and close the hood.
- Power up the vehicle and perform a test drive. The BMS will now begin relearning the battery parameters. It may take a few drive cycles for the range estimate to be accurate again.
Again, this is a general procedure and some of the steps may be different for your specific vehicle. When in doubt, have the reset performed by a qualified technician to avoid damaging any components.
How to Reset the BMS Using an OBD Scanner
The exact steps may vary by vehicle make and model, but here is the general process to reset a BMS with a compatible OBD scan tool:
- Fully charge the vehicle’s high voltage battery using a Level 2 charger.
- Connect the OBD scanner to the vehicle’s OBD-II diagnostic port, usually located under the dashboard. Power on the scanner.
- Navigate through the scanner’s menus to locate the BMS reset function. This may be under a “Special Functions”, “Maintenance”, or “Battery” menu.
- Initiate the BMS reset command from the scan tool and wait for the process to complete. The vehicle may need to be in a specific power mode for the reset to be allowed.
- Once the reset is finished, disconnect the scan tool and perform a test drive. The BMS will now relearn the battery parameters, which may take a few drive cycles.
Some popular OBD scanners with BMS reset capabilities for various makes and models include:
- iSmartEV P01 and P03 – dedicated battery diagnostic tools for EVs
- iSmartLink D01 and iSmartIMMO 801 – general OBD2 scanners with BMS reset
- Nexas NS202 – supports battery registration and BMS reset
- LAUNCH CR629 – has BMS reset for many brands like Audi, BMW, Ford, Lexus, Nissan, Toyota, VW
It’s important to verify your specific vehicle is supported before purchasing a tool. Resetting the BMS restores the system to its default settings, allowing it to optimize battery performance for the vehicle. But if done incorrectly, it could cause further issues.
Preventing BMS Issues
While BMS resets can be an effective troubleshooting tool, it’s obviously better to avoid BMS problems in the first place…. Here are a few tips for keeping your battery management system happy and healthy:
- Keep the battery properly charged. Avoid regularly letting the battery drain extremely low or keeping it at a high state of charge for long periods. Most EVs have charge setting options to limit the maximum charge level to 80-90% for daily use.
- Park in moderate temperatures when possible. Extreme heat and cold are hard on EV batteries. Park in a garage or shaded area to keep the battery closer to room temperature.
- Use the manufacturer’s recommended charging equipment. Cheap off-brand chargers can feed power in a way that confuses the BMS. Stick to charging stations and equipment that have been validated for your vehicle.
- Don’t ignore battery-related warning messages. If the BMS detects a genuine problem, get it checked out sooner rather than later. Continuing to drive with a battery issue risks damaging the pack beyond repair.
- Follow the recommended battery maintenance schedule. This usually involves having the battery inspected and tested at certain mileage intervals to catch any developing issues.
The Future of Battery Management Systems
As EVs continue to become more mainstream, battery management systems are a key area of research and development. Some of the latest trends and innovations in BMS technology include:
- Wireless BMS. Eliminating the heavy and expensive wiring harness between battery modules and the main BMS unit saves weight and cost. Wireless communication also enables more flexible and modular battery pack designs.
- Cloud connectivity. With an Internet connection, the BMS can log real-time battery health and usage data to the cloud for remote monitoring and analytics. This can help identify potential issues before they cause a breakdown and enable preventive maintenance.
- Machine learning. Leveraging artificial intelligence allows the BMS to learn from real-world driving data and continuously optimize its battery management algorithms…. This can help extend battery life and range without needing manual adjustments.
- Second-life applications. When an EV battery degrades to the point it no longer provides sufficient range, it often still has significant usable capacity left. Enhanced BMS capabilities can help enable these batteries to be repurposed for stationary energy storage in homes, businesses, and the electrical grid.
Conclusion
The battery management system is one of the unsung heroes of modern electric and hybrid vehicles, working tirelessly to keep the battery operating at peak safety and performance. While it’s a complex technology that can sometimes need a reset to clear glitches, taking good care of your vehicle’s battery can help avoid BMS issues.
As we charge forward into an increasingly electrified future, BMS capabilities will continue to advance, unlocking even greater range, reliability, and value from the humble battery pack. The next time you’re cruising effortlessly on electrons, take a moment to appreciate all the clever engineering that makes it possible!