For electric vehicle enthusiasts and those looking to repurpose Nissan Leaf batteries, accessing battery health information is crucial. The Nissan Leaf battery packs, known for their reliability, can offer a second life in various applications, from DIY power walls to electric vehicle conversions. However, determining the state-of-health (SOH) of a used battery is paramount before any project. This is where an OBD2 adapter for your Nissan Leaf battery becomes invaluable.
This guide will walk you through creating your own open-source OBD2 adapter specifically designed for Nissan Leaf batteries. This handy gadget allows you to directly interface with the battery management system (BMS) and retrieve essential data, including the battery’s SOH, cell voltages, temperatures, and more. Whether you’re evaluating a battery for purchase or monitoring the health of a battery already in use, this DIY adapter and readily available software like Leafspy empower you with critical insights.
It’s important to note that Nissan Leaf batteries utilize different Yazaki connectors, referred to as B24 connectors in service manuals. There are primarily two versions you’ll encounter:
- 2011-2012 Nissan Leaf batteries: These use a 21-pin B24 connector.
- 2013-2019 Nissan Leaf batteries: These utilize a 36-pin B24 connector.
Ensure you identify the correct connector type for your battery to proceed with the appropriate adapter build. Schematics for both versions are available to ensure correct wiring.
This image shows the 3D model file for the 2013 and newer Nissan Leaf battery B24 connector, highlighting its 36-pin configuration.
This image displays the 3D model file for the 2011 to 2012 Nissan Leaf battery B24 connector, characterized by its 21-pin layout and distinctive tabs for secure connection.
For reference, here is an image of a standard Yazaki 22-pin connector to provide visual context:
A close-up view of a Yazaki 22-pin connector, often used in automotive applications and similar to the B24 connector, serving as a visual reference for DIY builders.
Building Your OBD2 Adapter: What You’ll Need
Creating your own OBD2 adapter is a straightforward process, especially if you have some basic DIY electronics experience. Here’s a list of components you will need:
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3D-Printed B24 Connector Housing: You’ll need to 3D print the B24 connector housing. The STL files for both the 2013+ (36-pin) and 2011-2012 (21-pin) versions are available in this repository. If you don’t have access to a 3D printer, pre-made 36-pin connectors for 2013-2019 Leaf batteries can be purchased online (e.g., AliExpress – https://aliexpress.com/item/1005004180391674.html). If using a pre-made connector, you can skip steps 2 and 3.
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Dupont Connectors: These are essential for creating secure and solderless connections within the 3D-printed connector housing. Dupont connectors are commonly found in Arduino kits and older computer hardware. For the 2013+ version, you’ll need 1×2, 1×3, and 1×4 Dupont connectors. The 2011-2012 version requires only 1×1 connectors.
An image illustrating various Dupont style connectors, commonly used for prototyping and electronics projects, highlighting their application in the OBD2 adapter build.
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Adhesive: Superglue or epoxy is needed to securely affix the Dupont connectors inside the 3D-printed B24 housing.
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OBD2 Port and Pins: You’ll need a standard OBD2 port along with its connector pins. These can be sourced new from electronics suppliers or salvaged from scrap vehicles.
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Wiring: Standard automotive wiring to connect the B24 connector to the OBD2 port. The wire gauge isn’t critical but should be sufficient for low-voltage signals.
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12V Power Source: A 12V power source is required to power the BMS communication. A small lead-acid battery or a series of 18650 lithium-ion batteries (3 in series) will work effectively.
3D Printing Tips for the B24 Connector Housing
If you are 3D printing the B24 connector housing, here are some helpful tips for optimal results:
- Printing Materials: PLA (Polylactic Acid) and PETG (Polyethylene Terephthalate Glycol) filaments have been successfully used for this design. ABS (Acrylonitrile Butadiene Styrene) is also likely to be suitable.
- Print Speed: Print at a lower speed to ensure the mounting holes are precisely shaped for the Dupont connectors.
- Layer Height: Layer height is not critical. The connector will function well with layer heights of 0.12mm, 0.16mm, 0.20mm, or 0.28mm.
- Infill: An infill setting above 20% is sufficient for structural integrity.
- Supports: No supports are needed for printing this design.
- Print Time: Printing typically takes around 1.5 hours, depending on your printer settings and material.
Step-by-Step Assembly Guide
Follow these detailed instructions to assemble your Nissan Leaf battery OBD2 adapter:
- Gather Components: Ensure you have all the necessary parts listed in the “What You’ll Need” section.
- Prepare the B24 Connector Housing: Obtain the correct 3D-printed B24 connector for your battery (2013+ or 2011-2012) from the repository.
- Install Dupont Connectors: Carefully attach the Dupont connectors to the 3D-printed B24 connector housing. Use superglue or epoxy to secure them in place. Apply the adhesive sparingly to avoid getting any glue inside the connector pin areas.
- Wire to OBD2 Port: Once the adhesive is dry, connect the B24 connector wiring to the OBD2 port wiring. Refer to the schematic diagrams provided in the repository for the correct pin assignments for both 2013+ and 2011-2012 versions. Solder or crimp the wires together for secure connections.
- Power Up: Connect your 12V power source to the designated power pins on the B24 connector according to the schematic.
- Connect and Read Data: Plug an OBD2 Bluetooth dongle into the OBD2 port of your adapter. Open Leafspy (or a similar OBD2 diagnostic app) on your smartphone or tablet. In Leafspy settings, switch to ‘BMS only’ mode. This option is typically found in the vehicle model selection menu, often located above the 2010 model year option.
If all connections are correct, Leafspy should now communicate with the Nissan Leaf battery BMS and display battery data.
A photograph showcasing the fully assembled DIY OBD2 adapter connected to a Nissan Leaf battery, ready for diagnostic data retrieval and battery health analysis.
A screenshot of the Leafspy application displaying battery management system data in ‘BMS only’ mode, illustrating the successful connection and data reading via the DIY OBD2 adapter.
Wiring Schematics
Refer to the following schematics for wiring the 2013+ connector to the OBD2 port:
A detailed wiring diagram illustrating the pin connections between the 2013 and newer Nissan Leaf battery B24 connector and a standard OBD2 port, essential for proper adapter assembly.
For the 2011-2012 version, the wiring is similar, but be sure to consult the specific 2011-2012 B24 connector pinout diagram available here: 2011-2012 pinouts.
With your DIY OBD2 adapter, you can now easily monitor the health and performance of your Nissan Leaf battery, making informed decisions for your projects and ensuring optimal battery utilization.
