Understanding, Preventing, and Resolving Issues for Reliable Operation
Small PV + storage systems—typically 5–50 kW PV with 10–100 kWh storage—are widely deployed in small commercial, industrial, and remote applications. While these systems are modular and compact, early deployments reveal recurring failure modes that affect reliability, performance, and lifespan.
This article highlights the most common failure modes, their root causes, and practical mitigation strategies. The goal is to help EPCs, system integrators, and facility operators improve system uptime, reduce maintenance costs, and replicate successful deployments.
1. Electrical Connection Failures
Symptoms:
- PCS or BMS alarms
- Intermittent power loss
- Overheating of terminals or busbars
Causes:
- Loose lugs or connectors
- Incorrect torque on DC/AC terminals
- Oxidation or corrosion in humid environments
- Improper cable sizing → voltage drop
Mitigation:
- Follow standardized torque specifications
- Use corrosion-resistant terminals
- Label all cables for maintenance
- Limit DC voltage drop to <2% for low-voltage systems
Field Insight:
In several 10–30 kW installations, correcting terminal torque reduced PCS trip alarms by over 70%.
2. Battery Module Issues
Common Failures:
- Cell imbalance
- Over/under-voltage
- Premature capacity loss
- Thermal hotspots
Root Causes:
- Uneven SOC cycling
- Improper temperature management
- Aging or poor-quality cells
- BMS misconfiguration
Preventive Measures:
- Ensure 20–90% SOC operation range
- Install multiple temperature sensors per module
- Regular balancing via BMS
- Routine SOH evaluation
Example:
A 28 kWh LFP system in a workshop showed SOC drift after one month due to high summer temperatures. Adding airflow ducts and enabling daily balancing corrected the problem, restoring module health.
3. PCS / Inverter Faults
Typical Symptoms:
- Unexpected shutdowns
- Overcurrent or overvoltage trips
- Communication loss with EMS
Root Causes:
- Incorrect load or surge current estimation
- Grid voltage/frequency out of PCS limits
- Firmware mismatch or misconfigured parameters
Mitigation:
- Pre-deployment load logging (3–5 days)
- Correct AC wiring and CT installation
- Maintain firmware version consistency
- Use standard commissioning templates
Field Example:
During a 12 kW installation, the inverter tripped repeatedly due to misaligned CT polarity. Correcting the phase order and reapplying the commissioning profile resolved the issue immediately.
4. Communication and EMS Failures
Symptoms:
- EMS cannot read battery SOC
- Modules appear offline
- Alarms not reported
Causes:
- RS485/CAN bus wiring errors
- Protocol version mismatch
- Long cable runs causing signal degradation
Solutions:
- Standardize communication cabling
- Use protocol templates for EMS/BMS integration
- Implement signal repeaters for longer runs
Observation:
Early deployments without standardized communication templates experienced 15–20% more alarm false positives in the first month.
5. Thermal Management Failures
Symptoms:
- Battery hotspots
- PCS derating
- Early component aging
Causes:
- Poor airflow in cabinets
- Direct sun exposure
- High ambient temperature without cooling
Mitigation:
- Design airflow pathways in enclosure
- Use ventilation fans or passive ducts
- Separate inverter heat from battery modules
- Perform thermal imaging during commissioning
Example:
A 40 kWh system in an industrial building showed a 12°C gradient between top and bottom modules. Adding a small fan and ducting reduced the hotspot, improving cycle life prediction by 25%.
6. Environmental and Site-Related Failures
Issues:
- Water ingress, dust, chemical exposure
- Inadequate grounding
- Vibrations causing loose terminals
Mitigation:
- IP-rated enclosures (IP54+)
- Grounding and equipotential bonding
- Vibration-resistant mounting
Lesson:
Even small PV + storage modules fail prematurely when installed in outdoor enclosures without weatherproofing.
7. Human Error / Operational Mistakes
Common Errors:
- Improper commissioning sequences
- Ignoring SOPs during maintenance
- Incorrect load allocation
- Misunderstanding backup capacity
Prevention:
- Technician training manuals
- Step-by-step commissioning checklists
- Standard operating procedures for maintenance and load management
Field Insight:
Most early failures in small systems were preventable human errors rather than hardware defects.
8. Summary Table of Common Failure Modes
| Failure Mode | Typical Symptoms | Root Causes | Mitigation |
|---|---|---|---|
| Electrical connections | Trip alarms, overheating | Loose/corroded terminals, high current | Torque verification, corrosion-resistant lugs, cable labeling |
| Battery module | SOC drift, imbalance, hotspots | High temp, uneven cycling | Thermal management, BMS balancing, SOC limits |
| PCS / inverter | Shutdown, overload | Misconfigured parameters, surge loads | Commissioning template, load logging, firmware consistency |
| Communication | Offline modules, missing alarms | Wiring errors, protocol mismatch | Standard cables, EMS/BMS protocol templates, repeaters |
| Thermal | Hotspots, derating | Poor airflow, high ambient | Enclosure design, fans/ducts, thermal imaging |
| Environmental | Water/dust ingress | Poor enclosure | IP-rated cabinets, grounding, vibration mounts |
| Human error | Misoperation, wrong sequences | Training gaps | SOPs, checklists, manuals |
9. Key Lessons for EPCs and Operators
- Standardize installation templates to prevent common wiring and thermal issues.
- Pre-deployment load analysis is critical for inverter/PCS sizing.
- Modular design allows isolation and continued operation during troubleshooting.
- BMS + EMS integration must follow predefined protocols to reduce communication errors.
- Preventive maintenance and technician training reduce >50% of field failures.
Small PV + storage systems offer significant benefits in commercial and industrial environments. However, early deployments reveal that most failures are predictable and preventable. By understanding common failure modes, implementing standardized installation and monitoring procedures, and training field technicians, EPCs and operators can ensure reliable, long-term operation and replicate successful systems across multiple sites.
