For car enthusiasts and DIY mechanics, tasks like ECU programming and module updates are becoming increasingly common. However, these procedures demand a stable and reliable power supply to prevent interruptions and potential damage to your vehicle’s electronic systems. Low voltage during programming can lead to various issues, including corrupted software and bricked modules. Investing in a professional car power supply can be expensive, often ranging from $300 to $700 for brands like MST-80 or Schumacher INC-700A. Fortunately, there’s a budget-friendly and highly effective alternative: repurposing a server-grade power supply.
Server power supplies offer several advantages for use as a Car Power Supply For Programming:
- Inexpensive: Significantly cheaper than dedicated car programming power supplies.
- High Amperage: Provides ample power for even the most demanding programming tasks.
- Efficient: Designed for continuous operation and reliable power delivery.
This guide will walk you through building your own car power supply for programming using an HP DPS-1200FB server power supply. This DIY project delivers professional-grade power at a fraction of the cost.
Here’s a look at the finished car power supply for programming:
Understanding Power Output:
It’s important to note that the power output of the HP DPS-1200FB power supply varies based on your mains voltage. In regions with 120V power supply (like Canada and the USA), it will deliver a maximum of 75A at 12V (or approximately 64A at 14.2V, which is ideal for car programming). For those in 220V regions, the power supply can reach its full potential of 100A at 12V (or 85A at 14.2V).
Parts List for Your DIY Car Power Supply:
Here’s a breakdown of the components needed for this project, keeping the cost under $100:
- HP DPS-1200FB Power Supply (HSTNS-PD11): Around $40 from online marketplaces like eBay or Kijiji.
- LCD Digital Display Multimeter (6.5-100V, 0-100A): Approximately $25 from Amazon or similar retailers. This allows you to monitor voltage and current output.
- Round Rocker Switch: About $5 for an on/off switch.
- 8AWG Booster Cables: Around $16 for a set from automotive stores like Canadian Tire or auto parts suppliers.
- 8AWG Wire Lug Ring Clamps: Approximately $5 per pair for connecting to the power supply and battery terminals.
- Old Case (Optional): Repurpose an old case, like an electric stapler case, for free to house the power supply components.
- Solid Core Wire (Various Colors): Scrap wire from your workshop or inexpensive to purchase.
- 22k Resistor: For modifying the power supply to output the correct voltage.
- 82k and 18k Resistors: For adjusting voltage regulation and overcoming over-voltage protection (OVP). (Note: 75k and 15k are ideal, but 82k and 18k are acceptable substitutes).
Total Estimated Cost: Approximately $91
Step-by-Step Guide to Building Your Car Power Supply for Programming:
1. Resistor Modification for Power-On:
To enable the power supply, you need to apply a load to specific pins. Solder a 22k resistor between pins 33 and 32 on the power supply. Some guides suggest a 1k resistor between pins 36 and 33, but this method can be less reliable due to internal circuit behavior.
2. Accessing the Internal Circuit Board:
Open the power supply casing. Be careful when handling electronic components. The edge circuit board inside is responsible for voltage adjustment and monitoring.
3. Modifying Voltage Regulation and OVP:
To achieve a stable 14V output suitable for car programming and bypass the Over Voltage Protection (OVP), you’ll need to modify the regulation circuitry. Solder an 82k resistor and an 18k resistor as shown in the images below. These resistors adjust the voltage potentiometer’s range, allowing you to set the desired 14V output. Ensure to insulate the resistors with electrical tape or Kapton tape to prevent short circuits.
4. Adjusting Output Voltage:
Use the potentiometer (pot) on the circuit board to adjust the output voltage. Set it to approximately 14.2V. Remember that the voltage may slightly decrease as amperage increases under load.
5. Wiring and Assembly:
- Cut a length of 8AWG booster cable (about 1 meter) for connecting the power supply to your car’s battery clamps. While heavier gauge cable is preferable for higher amperage, 8AWG is manageable for soldering and handling.
- Install the SPST rocker switch to control the 14V output. Wire it to complete the circuit between pin 36 and ground, effectively acting as an on/off switch for the power output.
- Use zip ties to secure the internal circuitry and wiring within the case. Ensure wires connecting the top and bottom halves of the case have enough slack to prevent strain when closing.
- Cut a vent hole for the power supply fan to ensure proper cooling.
Usage and Safety Notes:
- Crucial! Power On Sequence: ALWAYS TURN ON THE POWER SUPPLY BEFORE CONNECTING IT TO YOUR CAR. This prevents potential back-feeding from the car battery into the power supply, which it is not designed to handle without additional protection circuitry.
- No Reverse Polarity or Short Circuit Protection: This DIY power supply lacks reverse polarity and short circuit protection. Exercise extreme caution when connecting to your car and avoid shorting the output clamps. Fusing the output is highly recommended for added safety, but not covered in this basic guide.
- Fan Operation: The power supply fan will remain running as long as the power supply is plugged into the mains, even when the output is switched off. This is normal.
- Discharge Time: Allow approximately 20 seconds for the internal capacitors to discharge after turning off the power supply. Avoid touching the clamps together or placing them down until the voltmeter reading confirms the voltage has dropped to a safe level.
Conclusion:
Building your own car power supply for programming using a server power supply is a rewarding and cost-effective project. For under $100 and a few hours of DIY work, you can have a powerful and reliable power source for all your car programming and diagnostic needs. This project is ideal for those comfortable with basic electronics and soldering. Always prioritize safety and double-check your wiring to ensure proper operation and protect your vehicle’s sensitive electronics. This DIY car power supply for programming will ensure stable voltage, preventing issues and saving you money compared to expensive commercial alternatives.
