FNIRSI FNAC-28 USB Charger Load Testing Guide Malaysia

Introduction

USB chargers are widely used to power smartphones, tablets, wireless accessories, portable electronics and other USB-powered devices.

A USB charger may appear to operate normally when no device is connected, but its output performance can change when electrical current is drawn.

For example, a charger may provide approximately 5V under a light load but experience excessive voltage reduction, intermittent output or protection shutdown when connected to a higher-current device.

These symptoms may indicate charger output limitations, poor voltage regulation, connector problems or unsuitable operating conditions.

For electronics repair workshops, USB charger retailers and technicians, load testing provides a more practical evaluation than simply checking the charger's output voltage without a load.

The FNIRSI FNAC-28 USB Tester can measure compatible USB voltage, current and power while a separate suitable electronic load draws current from the charger.

This guide explains USB charger load testing, how to perform controlled measurements and how to interpret the results.

1. What Is USB Charger Load Testing?

USB charger load testing is a procedure used to observe how a USB power supply performs while delivering electrical current to a connected load.

A suitable electronic load can be used to draw controlled current from the charger.

Technicians can then monitor:

• USB Output Voltage

• Output Current

• Electrical Power

• Voltage Regulation Under Load

• Output Stability

• Protection Behaviour

• Performance Near Rated Current

The objective is to determine whether the charger behaves as expected under specified operating conditions.

A charger that displays the correct voltage without a load has not necessarily demonstrated its ability to deliver its rated output current.

2. Why Is Load Testing Important?

A charger may have several operating limitations that are not obvious during a simple no-load measurement.

Possible problems include:

Insufficient Output Current

The charger may be unable to supply the required current under certain conditions.

Excessive Voltage Reduction

Output voltage may decrease significantly as current increases.

Overload Protection Activation

The charger may shut down or limit current when its protection system operates.

Thermal Limitations

Some chargers reduce output power when internal temperature becomes excessive.

Poor Connector Contact

A loose or damaged USB connector can cause unstable electrical measurements.

Load testing helps technicians observe these behaviours under controlled conditions.

3. FNIRSI FNAC-28 Main Specifications

The FNIRSI FNAC-28 measures electrical parameters in compatible USB charging arrangements.

It is not itself a programmable electronic load.

A separate suitable load is required for controlled current testing.

4. Equipment Required for USB Charger Load Testing

A practical test arrangement may include:

All accessories must be suitable for the intended voltage, current and connector configuration.

Avoid using damaged cables or improvised connections.

5. Basic USB Charger Load Testing Setup

A simplified test arrangement is:

USB Charger -> FNIRSI FNAC-28 -> Compatible Electronic Load

The charger supplies electrical power.

The FNIRSI FNAC-28 measures voltage and current at its measurement point.

The electronic load draws controlled current.

Important Testing Considerations

• Confirm the charger output rating.

• Confirm the tester operating limits.

• Confirm the electronic load rating.

• Use suitable USB connectors and cables.

• Begin with a low current.

• Increase the load gradually.

• Stop testing if abnormal heating or unsafe behaviour occurs.

Never exceed the lowest applicable rating of the charger, tester, load or connecting accessories.

6. Step-by-Step USB Charger Load Testing Procedure

Step 1 - Inspect the Charger

Check for damaged housing, bent pins, loose USB connectors or signs of overheating.

Do not energise visibly unsafe equipment.

Step 2 - Read the Charger Output Specifications

For example, a charger may be rated:

Output: 5V, 2A

Its nominal rated output power is:

5V x 2A = 10W

Step 3 - Prepare the FNIRSI FNAC-28

Connect the tester according to its operating instructions.

Step 4 - Connect the Electronic Load

Ensure the load is configured for a suitable current-controlled test.

Step 5 - Start with a Low Load

For a 5V, 2A charger, an illustrative starting current is 0.2A.

Step 6 - Increase Current Gradually

Possible test points include:

• 0.2A

• 0.5A

• 1.0A

• 1.5A

• 2.0A

These values are examples for a charger rated at 2A.

Do not apply the same test current to a charger with a lower rating.

Step 7 - Record Voltage, Current and Power

Observe how the output changes at each test point.

Step 8 - Evaluate the Results

Compare measurements with the charger's applicable specifications and manufacturer requirements.

Do not classify a charger as defective based only on an arbitrary voltage threshold.

7. Example - Testing a 5V 2A USB Charger

Consider a hypothetical charger rated at 5V and 2A.

The following table illustrates a possible load test.

These are illustrative measurements, not actual FNIRSI FNAC-28 test results.

The output voltage decreases slightly as current increases.

This behaviour may be normal depending on the charger specification and measurement arrangement.

The key question is whether the output remains within the manufacturer's specified limits under the defined load conditions.

8. How to Calculate USB Charger Output Power

The basic electrical power formula is:

Power (W) = Voltage (V) x Current (A)

For example:

Measured voltage: 5.02V

Measured current: 1.50A

Calculated output power:

5.02V x 1.50A = 7.53W

Another example:

Measured voltage: 9.0V

Measured current: 2.0A

Calculated output power:

9.0V x 2.0A = 18W

The FNIRSI FNAC-28 can display electrical measurements for compatible USB charging arrangements.

Instantaneous output power should not be confused with accumulated energy measured in Wh.

9. Understanding Voltage Regulation Under Load

Voltage regulation describes how a power supply maintains its intended output voltage as operating conditions change.

A charger with suitable regulation should maintain output within its specified limits across the applicable operating range.

However, a voltage reading measured through a USB cable can include cable and connector losses.

Example

Voltage near charger output: 5.05V

Voltage near electronic load: 4.90V

Current: 2A

Calculated voltage drop:

5.05V - 4.90V = 0.15V

This difference may be caused by resistance in the connection path.

To distinguish charger voltage regulation from cable voltage drop, use appropriate measurement points under equivalent load conditions.

A single reading from one test location is insufficient to isolate both effects.

10. What Happens When a Charger Is Overloaded?

USB chargers are designed to operate within specified output limits.

If a connected load requests excessive current, the charger may respond in different ways.

Possible behaviours include:

• Current Limiting

• Voltage Reduction

• Output Shutdown

• Automatic Restart

• Thermal Protection

• Overload Protection

The exact behaviour depends on the charger design.

Important Safety Note

Routine load testing should remain within the charger's rated operating conditions.

Intentional overload or protection testing requires appropriate equipment, manufacturer procedures and a controlled testing environment.

Do not deliberately exceed charger ratings simply to observe whether protection activates.

11. Testing USB Chargers with Multiple Output Ports

Some chargers include two or more USB output ports.

For example:

• USB-A Port

• USB-C Port

• Multiple USB-C Ports

The charger's total available power may be shared between ports.

A charger advertised as 65W may not deliver 65W from every port simultaneously.

Recommended Procedure

1. Read the charger's port-specific output ratings.

2. Test one port under suitable load conditions.

3. Record voltage, current and power.

4. Repeat for other compatible ports.

5. Check the manufacturer's combined-output specifications.

6. Compare the results with the applicable operating limits.

Example Multiport Charger

These figures are hypothetical.

Actual power allocation depends on the charger model.

Do not assume that the maximum advertised wattage is available simultaneously from every output port.

12. Load Testing USB-A vs USB-C Chargers

USB-A and USB-C charging systems may use different power delivery methods.

USB-A Charging

USB-A chargers commonly support conventional 5V charging and selected proprietary fast-charging technologies.

USB-C Charging

USB-C chargers may support conventional charging, USB Power Delivery or other compatible charging arrangements.

However, USB-C does not automatically mean that USB PD is supported.

Important FNIRSI FNAC-28 Limitation

The FNIRSI FNAC-28 does not support USB PD active triggering or USB PD packet capture.

Therefore, detailed USB PD power contract testing requires suitable additional equipment.

For high-power USB-C load testing, the test arrangement must support the required charging negotiation and cable current rating.

13. Common USB Charger Load Testing Problems

Problem 1 - Charger Voltage Drops at Higher Current

Possible causes include output regulation limitations, excessive connection resistance or operation beyond the intended rating.

Recommended Action: Verify the charger rating and repeat the test with suitable connections.

Problem 2 - Charger Shuts Down During Testing

Possible causes include overload protection, thermal protection or internal faults.

Recommended Action: Stop the test and investigate the operating conditions.

Problem 3 - Measured Current Is Lower Than the Load Setting

Possible causes include current limiting, voltage reduction or an unsuitable electronic load configuration.

Recommended Action: Check the load operating mode and equipment ratings.

Problem 4 - Voltage Changes When Another USB Port Is Used

Possible causes include shared power allocation.

Recommended Action: Review the charger's combined-output specifications.

Problem 5 - Charger Does Not Enter Fast-Charging Mode

Possible causes include incompatible charging protocols or missing negotiation.

Recommended Action: Confirm the charging standard and use suitable protocol testing equipment.

14. Case Study - USB Charger Fails at Rated Load

Customer Complaint

A customer reports that a USB charger operates normally with a small accessory but fails when charging a higher-current device.

Charger Rating

5V, 2A

Test Procedure

The technician connects a suitable electronic load and gradually increases current.

Hypothetical Measurements

Interpretation

The larger voltage reduction near the rated current may indicate a problem requiring further investigation.

Possible causes include charger regulation limitations or excessive connection resistance.

Recommended Action

Repeat the test using suitable known-good connections and verify the voltage at the appropriate measurement points.

If abnormal behaviour persists, remove the suspected charger from service pending further evaluation.

This is an illustrative case study, not a documented customer repair.

15. How to Create a USB Charger Load Test Report

A simple test report can help electronics repair shops document results.

Suggested Report

Consistent test records make it easier to compare chargers and identify changes in output behaviour.

16. Common Mistakes During USB Charger Load Testing

Mistake 1 - Testing Only Without a Load

No-load voltage does not confirm rated output performance.

Better Method: Test under suitable controlled loading conditions.

Mistake 2 - Exceeding the Charger Rating

Excessive current can activate protection or create unsafe conditions.

Better Method: Remain within specified operating limits.

Mistake 3 - Ignoring Cable Resistance

Cable voltage drop can affect the measurement.

Better Method: Use suitable short connections and appropriate measurement points.

Mistake 4 - Assuming USB-C Automatically Supports USB PD

Connector type does not establish protocol support.

Better Method: Verify the charger specifications.

Mistake 5 - Using a Smartphone as a Constant Load

Smartphones automatically change their charging current.

Better Method: Use a suitable electronic load for repeatable measurements.

Mistake 6 - Treating the FNIRSI FNAC-28 as an Electronic Load

The tester measures electrical parameters but does not replace a programmable load.

Better Method: Use the FNAC-28 together with suitable load equipment.

17. Applications for Electronics Technicians in Malaysia

Electronics Repair Shops

Investigate charger performance complaints and verify suitable replacement chargers.

Mobile Phone Service Centres

Compare charger output behaviour under controlled conditions.

USB Charger Retailers

Demonstrate electrical output measurements and explain charger specifications.

Power Supply Technicians

Perform preliminary checks on compatible low-voltage USB supplies.

Electronics Training Centres

Teach voltage regulation, current loading and power calculations.

DIY Electronics Users

Learn practical USB electrical measurement techniques using suitable equipment.

18. Where to Buy FNIRSI FNAC-28 USB Charger Tester in Malaysia?

MTM Precision Sdn Bhd supplies electronic testing and measuring instruments for technical applications throughout Malaysia.

Customers looking for a FNIRSI FNAC-28 USB Charger Tester Malaysia can contact MTM Precision for product pricing, stock availability and suitable instrument recommendations.

The FNAC-28 is useful for USB charger output measurement, controlled load testing support, charging cable comparisons and compatible power bank troubleshooting.

MTM Precision serves customers in Kuala Lumpur, Selangor, Johor, Penang, Melaka, Negeri Sembilan, Perak, Pahang, Kedah, Kelantan, Terengganu, Perlis, Sabah and Sarawak.

Please contact our team to confirm current stock and delivery arrangements.

Frequently Asked Questions

Q1. What is USB charger load testing?

It is the process of measuring charger output behaviour while a suitable load draws electrical current.

Q2. Can FNIRSI FNAC-28 perform USB charger load testing?

It can measure compatible USB voltage, current and power while a separate suitable electronic load is used.

Q3. Is FNIRSI FNAC-28 an electronic load?

No. It is a USB measurement instrument, not a programmable electronic load.

Q4. Why does charger voltage drop under load?

Possible causes include cable resistance, connector losses, charger regulation limitations or protection behaviour.

Q5. Can FNIRSI FNAC-28 test a 5V 2A USB charger?

Yes, when used in a compatible test arrangement within the specified instrument ratings.

Q6. Can FNIRSI FNAC-28 verify a 65W USB-C PD charger?

It can measure compatible USB electrical conditions, but complete USB PD rated-output verification may require dedicated PD negotiation equipment.

Q7. Can FNIRSI FNAC-28 measure charger output power?

Yes. It provides voltage, current and power measurements.

Q8. Is USB charger load testing useful for repair shops?

Yes. It helps technicians evaluate charger behaviour under controlled electrical loads.

Q9. Should technicians deliberately overload USB chargers?

Not during routine testing. Intentional overload testing requires suitable equipment and controlled procedures.

Q10. Where can I enquire about FNIRSI FNAC-28 in Malaysia?

Contact MTM Precision Sdn Bhd in Puchong, Selangor, for product pricing and availability.

Contact MTM Precision Sdn Bhd

For FNIRSI FNAC-28 USB Tester Malaysia, USB charger load testing equipment and electronics measurement instrument enquiries:

MTM Precision Sdn Bhd

Showroom & Service Centre

No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia.

Tel: 03-8080 7172

WhatsApp: +6016-660 7346

Email: mtmpre@yahoo.com

Website: www.mtmpre.com.my

Contact MTM Precision today for FNIRSI FNAC-28 pricing, availability and suitable USB charger testing equipment recommendations in Malaysia.

Conclusion

USB charger load testing provides a practical way to evaluate electrical output behaviour under controlled conditions.

A charger that produces the correct voltage without a load may still experience problems when supplying higher current.

The FNIRSI FNAC-28 USB Tester can measure compatible USB voltage, current and power when used together with suitable electronic load equipment.

By comparing measurements at different load levels and checking the charger's manufacturer specifications, technicians can investigate voltage regulation, output stability and charger performance more systematically.

For customers searching for USB Charger Load Testing Malaysia, USB Electronic Load Testing Malaysia or FNIRSI FNAC-28 Malaysia, MTM Precision Sdn Bhd can assist with product enquiries and suitable electronics testing equipment recommendations.