Replacing an Electrical Timer with a Mechanical Timer in Battery Chargers

Introduction to Timer Replacement in Battery Chargers

Battery chargers, especially those used in workshops or industrial settings, often rely on timers to control charging cycles. Over time, these timers may need replacement due to wear or cost concerns. In this guide, we explore the process of replacing an electrical timer in a charger with a more economical mechanical timer. This tutorial is based on practical experience with an Associated 69A charger and offers detailed wiring insights, tools needed, and troubleshooting tips.

Why Replace an Electrical Timer with a Mechanical Timer?

Cost Considerations

Electrical timers in chargers generally cost between $50 and $55, while mechanical timers are priced under $25, nearly half the price. OEM replacement chargers can cost around $70 or more. Choosing a mechanical timer can lead to significant savings without compromising functionality.

Power Requirements and Functionality

Electrical timers require a small amount of power to operate their internal motor, which can complicate wiring and maintenance. Mechanical timers, in contrast, operate through a wound main spring and do not require electricity to function. They act purely as circuit interrupters, making them simpler and more reliable in many cases.

Understanding the Differences: Electrical Timer vs Mechanical Timer

Electrical Timer

• Powered by the charger’s AC supply.
• Uses an internal motor to control timing.
• More complex wiring and higher cost.

Mechanical Timer

• Operates mechanically via a wound spring.
• No power needed for timer operation itself.
• Simple circuit interrupter acting as a switch.
• Cheaper and easier to maintain.

Tools and Materials Needed for Replacement

• Mechanical timer compatible with your charger model.
• Screwdrivers (Phillips and flathead).
• Wire cutters and strippers.
• Cable ties for wire management.
• Multimeter for testing voltage and continuity.
• Drill (optional, for adjusting mounting holes).

Step-by-Step Guide to Replacing the Timer

1. Preparing the Charger

• Unplug the charger and open the casing carefully.
• Identify the existing electrical timer and take note of wiring connections.
• Remove cable ties or other wire management tools obstructing access.

2. Assessing the Wiring

• Locate the AC power input wires (usually black and white).
• Identify which wires feed the timer motor, fan motor, and transformer.
• Understand that the electrical timer switches power from the incoming AC line to the transformer and fan.

3. Removing the Electrical Timer

• Depress the spring-loaded knob on the timer shaft to remove the knob.
• Unscrew the timer from its mounting.
• Disconnect the wires:
  • The incoming power wire from the AC cord (usually connected to the blue insulated terminal).
  • The output wire feeding the fan and transformer.
  • The wire powering the timer motor (this wire will be removed as it is unnecessary for mechanical timers).

4. Wiring the Mechanical Timer

• Connect the AC power wires to the two interchangeable terminals on the mechanical timer.
• The mechanical timer acts as a simple switch, so terminal polarity does not matter.
• Confirm that the wiring feeding the fan motor and transformer remains unchanged.
• Secure the timer in place, using a drill if necessary to adjust mounting holes.

5. Installing the Timer Knob

• Attach the push-on knob to the timer shaft, ensuring alignment with the “off” position on the charger panel.
• Confirm the knob fits snugly and can rotate smoothly.

6. Cable Management and Safety

• Use cable ties to bundle wires away from the fan blades to prevent damage.
• Ensure wires are secure but not overly tight to avoid damage.
• Recheck all connections for tightness and safety.

Testing and Final Checks

Testing the Charger

• Plug the charger into an AC outlet.
• Set the charger to a known voltage range (e.g., 12 volts low or high).
• Use a multimeter to check open circuit voltage at the output clamps.
• Turn the timer on and off to verify proper switching and voltage output.

Troubleshooting Tips

• If no voltage is detected, double-check wiring against the updated wiring diagram.
• Ensure the timer knob is in the “on” position during testing.
• Confirm that the timer is ticking, indicating mechanical operation.
• Check that wires are not interfering with the fan or other moving parts.

Wiring Diagram Explained

Original Electrical Timer Wiring

• White neutral wire from AC power splits to fan, switch, and timer motor.
• Black hot wire feeds directly into the electrical timer.
• Timer output wire feeds back into a wire nut connecting transformer and fan motor.

Modified Mechanical Timer Wiring

• The wire to the timer motor is removed as the mechanical timer does not require power.
• The mechanical timer switches the hot AC line directly to the transformer and fan.
• Neutral wiring remains unchanged.

Benefits of Using a Mechanical Timer

• Reliability: Fewer electronic components mean less chance of failure.
• Simplicity: Easier to understand and wire, ideal for DIY repairs.
• Cost-Effective: About half the price of electrical timers.
• No Power Draw: Mechanical operation reduces electrical load and potential issues.

Common Challenges and How to Overcome Them

Mounting the New Timer

Sometimes the mechanical timer screws do not fit perfectly due to small differences in hole sizes. Using a drill to clean or slightly enlarge holes can solve this issue quickly.

Aligning the Timer Knob

Mechanical timers and original electrical timers may have different knob orientations. Using a label to mark the “off” position on the charger panel helps align the knob correctly.

Wire Management

If wires are bulky or in the way, removing cable ties and repositioning wires with new ties ensures safe operation and prevents fan interference.

Final Thoughts: Is Mechanical Timer Replacement Right for You?

Replacing an electrical timer with a mechanical one in a battery charger is a practical upgrade for those looking to save money and simplify maintenance. While mechanical timers lack the electronic precision of their counterparts, they provide reliable operation with fewer components to fail. This makes them especially suitable for workshop chargers and basic industrial applications.

If you are comfortable with basic wiring and have the necessary tools, this replacement can be a straightforward and rewarding DIY project. Always remember to follow safety procedures when working with electrical equipment and consult a professional if you are unsure.

FAQ

Q1: Can I use any mechanical timer as a replacement?

No, it is important to choose a mechanical timer compatible with your charger’s voltage and mounting specifications.

Q2: Will the mechanical timer affect the charger’s performance?

No, performance remains consistent as the timer still acts as a circuit interrupter controlling power flow.

Q3: What should I do if the timer knob doesn’t align with the panel markings?

Use a label or marker to indicate the “off” position for clarity.

Q4: Is it safe to remove the timer motor wire?

Yes, mechanical timers do not require power to operate, so the wire that powered the timer motor is unnecessary.

About the Author

Rick from PLP Battery Supply shares his expertise in battery charger repair and maintenance. With years of hands-on experience, he provides clear, practical guidance to help users extend the life and efficiency of their charging equipment.