Implementing a Rechargeable RTC Battery Circuit for Nvidia Jetson Orin Nano

Issue Overview

The Nvidia Jetson Orin Nano development board supports only non-rechargeable batteries for its Real-Time Clock (RTC). Users are interested in implementing a rechargeable battery solution by designing a custom charging circuit on their base board. This modification would allow for a more sustainable and convenient power source for the RTC, potentially reducing the need for battery replacements and improving the overall user experience.

Possible Causes

The limitation of non-rechargeable batteries for the RTC on the Orin Nano could be due to several factors:

1. Design Constraints: The original design may have prioritized simplicity or cost-effectiveness over rechargeable capabilities.

2. Power Management: Non-rechargeable batteries might have been chosen for their specific voltage characteristics or long-term stability.

3. Safety Considerations: Rechargeable batteries require additional circuitry for proper charging and management, which may have been omitted to reduce complexity or potential safety risks.

4. Compatibility: The board’s power management system might not be designed to handle the charging cycles of rechargeable batteries.

Troubleshooting Steps, Solutions & Fixes

While the Orin Nano doesn’t natively support rechargeable RTC batteries, it is possible to implement a custom solution. Here are the steps and considerations for creating a rechargeable RTC battery circuit:

1. Verify Board Compatibility:

   • Review the Jetson Orin Nano technical documentation to ensure that adding a charging circuit won’t interfere with other board functions.
   • Check the voltage and current requirements for the RTC battery input on the Orin Nano.

2. Design the Charging Circuit:

   • Choose a suitable rechargeable battery (e.g., a small Li-ion or LiFePO4 cell) that matches the voltage requirements of the RTC.
   • Select a charging IC compatible with the chosen battery chemistry.
   • Design a circuit that includes:
     • The charging IC
     • Necessary passive components (resistors, capacitors)
     • Protection circuitry (over-voltage, over-current)
     • A voltage regulator if needed to match the RTC input voltage

3. Implement the Circuit:

   • Create a custom base board or expansion board that includes the charging circuit.
   • Ensure proper connections between the charging circuit, battery, and the Orin Nano’s RTC battery input.

4. Testing and Validation:

   • Thoroughly test the charging circuit in isolation before connecting it to the Orin Nano.
   • Verify that the circuit provides the correct voltage and current to the RTC input.
   • Monitor the battery’s charge and discharge cycles to ensure proper functionality.

5. Software Considerations:

   • Check if any software modifications are needed to support the rechargeable battery.
   • Implement battery monitoring if desired, possibly through I2C or GPIO connections.

6. Safety Precautions:

   • Include thermal protection in your design to prevent overheating.
   • Consider adding a battery disconnect feature for maintenance or emergencies.
   • Ensure proper ventilation for the battery and charging circuit.

7. Documentation:

   • Create detailed documentation of your custom solution for future reference and maintenance.
   • Include schematics, parts list, and any software modifications made.

It’s worth underlining that while this custom solution is possible, it may void warranties and should be approached with caution. Always prioritize safety when working with battery circuits.

For those not comfortable with creating a custom circuit, an alternative solution could be to use a super capacitor instead of a battery, which can provide power to the RTC for extended periods without the need for charging circuitry. However, this would require careful design consideration to ensure sufficient capacitance and proper interfacing with the Orin Nano.