Module 5: Diagnostics, Troubleshooting & Maintenance

24 sept. 2026

Introduction

Effective fault-finding identifies the underlying cause, corrects it once, verifies the repair and leaves a record that assists future work. Replacing components until a system operates again is costly, often fails to address the cause and destroys evidence. Many systems partners attend will have been installed by others. This module sets out a systematic and honest approach to diagnosis, repair and maintenance.

Learning outcomes

On completing this module, partners should be able to:

1. Apply a structured diagnostic method;
2. Select and use test instruments safely;
3. Use alarms, logs and monitoring data as evidence;
4. Diagnose common faults in PV arrays, inverters, batteries and AC circuits;
5. Use voltage-drop measurements to locate excessive resistance;
6. Assess an existing installation safely and fairly;
7. Repair the root cause and verify the repair;
8. Carry out preventive maintenance;
9. Report findings accurately and objectively.

5.1 Diagnostic method

Define the symptom. A complaint such as "the solar is not working well" must be established as a specific symptom, for example: "The inverter shuts down with a low-battery alarm at about 02:00 each night, since last month." The partner should establish what happens, when, how often, since when, and whether anything changed at that time.

Collect evidence. Alarm codes, event logs, settings and readings are recorded before any change is made. Restarting or resetting equipment may erase them.

Inspect safely. Signs of overheating, damage, water ingress, loose conductors and abnormal noise are noted, using safe isolation where equipment is opened (Module 2).

List and eliminate causes. Using knowledge of system operation, possible causes are listed and tests selected to eliminate as many as possible at each step. Useful techniques include comparison with a known good part of the system, comparison with baseline readings, and the half-split method: measuring at the midpoint of a circuit to determine in which half the fault lies. Faults should be reproduced only where this is safe.

Replacing the component that "usually fails" is not diagnosis. It adds cost, frequently leaves the cause in place and removes evidence.

5.2 Test instruments

Safe practice includes inspecting instruments and leads before use, selecting the function and range before connection, connecting the common lead first and removing it last, keeping fingers behind probe guards, and avoiding measurement in wet conditions.

5.3 Alarms, logs and monitoring

Alarm codes differ between manufacturers and models. The partner should record the exact code with a photograph, note the conditions (time, load, battery state, weather, grid and generator status), consult the correct manual, carry out only approved checks, and escalate with the evidence if the fault is not resolved. Clearing codes without understanding them, altering settings experimentally and factory resets destroy evidence and may introduce new faults.

Monitoring data shows system behaviour in the partner's absence: daily PV yield compared with the season and previous weeks (a sudden fall suggests a fault; a gradual fall suggests soiling or ageing), overnight battery state of charge, load profile and event history. These are compared with the baseline readings recorded at commissioning.

5.4 PV array faults

Before a fault is suspected, output should be compared with the time of day, cloud, temperature, soiling and season, using an irradiance meter or a comparable nearby system where available, and with the system's history and baseline readings.

Where identical strings share orientation and conditions, a string that performs significantly worse than the others indicates a fault within that string, since the conditions, inverter and settings are common to all.

5.5 Inverter faults

Where the inverter itself is faulty, the model, serial number, firmware version, fault codes, logs and photographs should be collected to support a warranty claim. Inverters retain stored charge and may lose warranty cover if opened without authorisation.

5.6 Battery faults

Loss of voltage along a path

Where 25.6 V is present at the battery terminals but 0 V at the inverter's battery input, the voltage is being lost between them. The path is checked point by point: battery fuse or breaker, isolator, lugs, conductors and inverter terminals. The fault lies between the last point at which the voltage is present and the first at which it is absent. Components outside this path cannot be the cause.

Voltage drop under load

A high-resistance connection may show no voltage difference with no load, since V = I × R and no current produces no drop. Under load, the resistance becomes apparent.

Worked example. At an 80 A load, the battery terminals read 25.6 V and the inverter input 23.0 V.

• Voltage lost: 25.6 − 23.0 = 2.6 V
• Path resistance: 2.6 ÷ 80 = 0.0325 Ω
• Power dissipated: 2.6 × 80 = 208 W, concentrated at the defective joint

The battery is maintaining its voltage; the inverter reports low battery because of losses in the path. The drop across each lug, fuse, breaker and conductor is measured to locate the fault, which must be corrected before any battery replacement is considered.

Reduced backup time

Since runtime equals usable energy divided by load, reduced backup results from increased load, reduced stored energy, losses, or changed settings.

Raising charge voltages or lowering cut-off limits conceals the symptom and may damage the battery.

BMS alarms

In lead-acid banks, a single weak block limits the string. Block voltages should be measured under load; a block significantly lower than the others is defective. New blocks should not be mixed with aged blocks.

5.7 AC and load faults

Any change to protection is considered only after the cause is known, and the device must continue to protect the cable (Module 2, unit 2.9).

RCD tripping

An RCD trips when current leaks to earth. Common causes are moisture in outdoor accessories, junction boxes or connectors (hence tripping in rain); damaged insulation; appliances with leakage to their enclosures, such as water heaters; and incorrect neutral–earth arrangements. The faulty circuit is identified by isolating circuits in turn, then the appliances on it; insulation resistance is tested; and the fault is repaired and tested before re-energisation. An RCD that trips in rain is providing protection against electric shock. Bypassing it or replacing it with a device that does not detect leakage removes that protection.

Motor starting

Where an inverter supplies normal loads but trips when a pump or compressor starts, the following are checked: the motor's starting current or power (typically 3 to 7 times running); the inverter's surge rating and duration; battery voltage during starting; and voltage drop in battery and motor cables. Remedies, such as a soft starter or variable-speed drive, larger conductors, battery replacement or a larger inverter, are design decisions for EcoStride.

Supply quality

Grid voltage outside the inverter's limits causes the grid to be rejected, and should be measured at different times and reported. Generators with unstable speed under load produce unstable frequency, which inverters commonly reject; servicing or adjustment of inverter settings within the manufacturer's limits may be required. On three-phase sites, imbalance between phases can overload one phase or inverter.

5.8 Assessment of existing installations

Many systems partners attend were installed without adequate design, protection or earthing. Wiring may not match any drawing; labels may be absent or wrong; protective devices may be AC-only on DC circuits, undersized or bypassed; earthing may be missing; and batteries may be damaged, mixed or overheating.

Before any work, the partner looks for immediate hazards: exposed live parts, burn marks, swollen batteries, melted insulation, bypassed protection and unsafe generator connections. Where a hazard is found, the partner makes the situation safe if it can be done safely, informs the customer clearly and reports to EcoStride immediately.

The assessment then proceeds as follows:

1. establish the customer's concerns and the history of the system;
2. record all components, ratings, labels and layout with photographs;
3. review alarm history, settings and monitoring data;
4. measure string voltages and currents, battery voltage at rest and under load, voltage drop, AC voltages, and insulation and earth resistance where safe;
5. compare the installation with the practice described in Modules 2 to 4;
6. classify the findings.

Findings must reflect the evidence. Problems must not be exaggerated to generate work or omitted to avoid difficult conversations. Previous installers should not be criticised; the problem and its significance should be described. Repairs and prices are not promised on site; EcoStride follows up with solutions. Measured facts are distinguished from opinions.

5.9 Repair and verification

Before repair, the circuit is isolated and proved dead (Module 2, unit 2.6). Replacement parts must match the original specification or the approved design. For warranty repairs, serial numbers, fault codes, logs, photographs and readings are collected first, and sealed equipment is not opened without authorisation from the manufacturer or EcoStride.

After a repair, such as tightening a loose battery terminal, the partner:

1. inspects related connections, which may have been installed in the same way;
2. examines the repaired joint and adjacent components for heat damage, replacing rather than re-tightening where necessary;
3. tests under the load conditions that produced the fault, including voltage drop across the joint;
4. checks for abnormal temperature after operation under load;
5. records the fault, cause, action and post-repair results.

5.10 Preventive maintenance

Modules are cleaned in the early morning or evening, when they are cooler and producing less current, since cold water on hot glass may cause cracking. Clean water and a soft brush or sponge are used; hard water, detergents and abrasives damage the anti-reflective coating. Modules must not be walked or knelt on, and all work-at-height controls apply (Module 2, unit 2.4). Cleaning may be required more frequently during the harmattan.

Connections loosen over time through thermal cycling. A sample of key terminals should be checked with a torque tool and a thermal check made under load.

5.11 Reporting

Service reports are submitted by WhatsApp in the standard format provided by EcoStride. Each report should state:

1. the fault reported and the symptom confirmed;
2. observations, measurements and alarm codes, with photographs;
3. the cause, based on the evidence, or a statement that it is not yet established;
4. the action taken and parts used;
5. results after repair, demonstrating operation under load;
6. any outstanding work and the reason;
7. recommendations, with safety hazards first.

A fault must never be reported as corrected when it is not, and findings must not be exaggerated or concealed. Errors discovered from earlier jobs are reported (Module 1, unit 1.10). Safety hazards are reported immediately, not at the end of the visit.

Case studies

The following cases are based on situations commonly encountered on Nigerian sites. Names and places are illustrative.

Case 1: Battery wrongly condemned. A school in Abeokuta was advised that its battery bank needed replacement. A partner measured 51.8 V at the battery terminals and 46.9 V at the inverter under load. A corroded lug on the main negative conductor was dropping almost 5 V; replacing it restored normal backup time. Principle: unit 5.6.

Case 2: Bypassed RCD. A restaurant's RCD tripped whenever it rained, and a previous electrician had bypassed it. A partner found water in a roof junction box with an unsealed cable entry. After sealing, drying and insulation testing, the RCD was reinstated and did not trip again. Principle: unit 5.7.

Case 3: Evidence-based assessment. A customer in Asaba had been told she needed a new inverter. The partner found the inverter serviceable and the array shaded by a newly installed water tank, and reported this with photographs and string readings, recommending relocation of three modules. Principle: units 5.4 and 5.8.

Relationship to performance rating

Practical activities

1. Practise converting a vague complaint into a precise symptom, using the questions in unit 5.1.
2. On an operating system, measure battery voltage at the terminals and at the inverter under load, and calculate the voltage drop and path resistance.
3. Measure and compare the currents of identical strings with a DC clamp meter.
4. Select three alarm codes from an inverter manual and record their meaning and the checks required.
5. Assess an existing installation using the procedure in unit 5.8 and classify the findings.
6. Write a service report for one of the case studies above, following unit 5.11.

Glossary