Quick Answer: Field maintenance technicians, EPC contractors, and system integrators use mobile monitoring applications to evaluate the operational status of off-grid solar energy storage systems. When an abnormal condition occurs, the Solar of Things APP displays real-time alarm codes generated by the hybrid inverter EMS or battery BMS, allowing engineers to identify whether the issue originates from the PV input, battery system, AC source, or communication network.
Solar inverter and battery APP alarm codes are diagnostic indicators generated by the Energy Management System (EMS) and Battery Management System (BMS) to identify abnormal operating conditions. Troubleshooting requires isolating the fault layer, including the PV DC input, battery protection system, AC grid or generator interface, and CAN/RS485 communication network, followed by systematic electrical measurements and parameter verification before clearing the alarm.
Understanding the root cause behind these alarm codes helps engineers avoid unnecessary component replacement and perform accurate field diagnostics for reliable long-term Solar ESS operation.
1. Understanding APP Alarm Architecture & BMS/EMS Data Flow
To effectively diagnose fault notifications on the Solar of Things APP, technicians must first understand how data moves from physical components through the BMS, hybrid inverter EMS, and communication gateway to the cloud interface. A Solar ESS operates on a multi-layer control architecture where cell-level monitoring, battery protection, energy dispatching, and remote telemetry functions work together.
[Battery Cells] ──────► [Slave BMS] ──────────────► [Master BMS]
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(CAN / RS485)
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[Solar PV Array] ──────► [Hybrid Inverter] ◄──► [EMS Control Logic]
[Utility / Generator] ──► │
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[Loads]
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[WiFi / 4G Gateway]
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[Solar of Things APP]
At the battery layer, each Battery Management System (BMS) continuously monitors cell voltage, battery temperature, charge and discharge current, State of Charge (SOC), and other safety parameters. When operating limits are exceeded, the BMS executes protective actions such as opening MOSFETs or contactors and transmits status data and alarm information through the CAN or RS485 communication bus to the hybrid inverter EMS.
The hybrid inverter houses the Energy Management System (EMS), which acts as the system-level control layer. The EMS aggregates battery telemetry from the BMS together with PV input data, MPPT operating conditions, AC source status, and load demand. It evaluates this information against configured operating strategies, including Solar-Battery-Utility priority and Time-of-Use scheduling, to control energy flow between PV, battery, grid, generator, and loads.
When an operational limit is exceeded, the inverter EMS or battery BMS generates the corresponding alarm status, records the fault event, and transmits diagnostic data through the WiFi or 4G communication gateway to the cloud platform. The Solar of Things APP then displays the alarm notification for remote troubleshooting.
| Telemetry Layer | Monitored Parameters | Primary Responsibility | Associated APP Alarms |
|---|---|---|---|
| Battery Management System (BMS) | Cell Voltage, Pack Delta V, Charge/Discharge Current, Cell Temperatures | Physical battery safety, cell balancing, short-circuit protection | Communication Loss, Cell Overvoltage, Low Temperature Lockout, Under-Voltage Disconnect |
| Energy Management System (EMS) | PV Array Voc/Isc, Bus Voltage, AC Frequency/Voltage, Temperature, Load Surge | Power routing strategy, grid/generator synchronization, inverter protection | PV Overvoltage, AC Overload, Bus Voltage High, Grid Frequency Out-of-Bounds |
| Cloud Telemetry & APP | Network Connection, Modbus Registers, User Parameter Thresholds | Data visualization, historical fault logging, remote alerts | Gateway Offline, Data Refresh Timeout, Parameter Out-of-Sync |
A critical distinction must be made between BMS protective actions and EMS operational alarms. The BMS focuses on battery-level safety protection, including cell voltage, current, and temperature limits. The EMS focuses on system-level energy management and responds to external operating conditions, such as excessive load demand, abnormal AC input conditions, or insufficient generator capacity.
2. Inverter-Side Critical Error Codes: Voltage, Current & Grid Alarms
Inverter-level fault codes typically indicate abnormal conditions related to the PV DC input, internal power conversion stage, battery DC interface, or AC input/output circuits. When analyzing inverter alarms on the ALL 4812000 Pro and ALL 486000 Pro hybrid inverters, field engineers must verify measured electrical parameters against the inverter specifications and configured EMS protection settings.
One of the most frequent winter commissioning errors is the PV Overvoltage alarm (Code E01). The ALL 4812000 Pro dual-MPPT platform operates within a 60V DC to 500V DC MPPT voltage range and has a maximum PV open-circuit voltage limit of 500V DC. Photovoltaic modules exhibit a negative temperature coefficient of open-circuit voltage (Voc), meaning the module voltage increases as cell temperature decreases.
2.1 PV String Voltage Cold-Weather Formula
When calculating maximum string Voc to prevent inverter damage and overvoltage alarms, technicians must apply the temperature coefficient calculation:
Voc,max = Voc,STC × [1 + (αVoc / 100) × (Tmin – 25)] × Nmodules
Where:
- Voc,max = Calculated string open-circuit voltage at minimum ambient temperature (V DC)
- Voc,STC = Rated module open-circuit voltage at Standard Test Conditions (V)
- αVoc = Temperature coefficient of open-circuit voltage (%/°C, typically negative)
- Tmin = Lowest expected site ambient temperature (°C)
- 25 = Standard Test Condition temperature (°C)
- Nmodules = Number of solar modules connected in series per string
Worked Engineering Example
An installer designs a solar array using 610W monocrystalline modules with a module Voc,STC of approximately 49V and a temperature coefficient αVoc of -0.27%/°C. The array consists of 11 modules per string installed in Eastern Europe, where the minimum winter ambient temperature reaches -15°C.
- Calculate temperature delta: Tmin – 25 = -15 – 25 = -40°C
- Calculate voltage multiplier: 1 + [(-0.27 / 100) × -40] = 1 + 0.108 = 1.108
- Calculate cold-weather module Voc: 49V × 1.108 = 54.29V DC
- Calculate total string Voc at -15°C: 54.29V DC × 11 modules = 597.2V DC
While the calculated 597.2V DC string voltage exceeds the inverter’s 500V DC maximum PV input limit, the inverter will trigger the E01 PV Overvoltage protection cutoff. Reducing the string length to fewer modules keeps the cold-weather Voc within the safe MPPT input range while maintaining sufficient operating voltage for efficient solar harvesting.
Another common fault code is Inverter Overload (Code E04). Hybrid inverters are designed to provide continuous AC output power and temporary surge capability for starting inductive loads such as water pumps, compressors, and air-conditioning systems. The ALL 4812000 Pro supports up to 22kVA surge power, while excessive startup current or prolonged overload conditions will cause the EMS to disconnect output power to protect the inverter power electronics.
| APP Code | Alarm Description | System Layer | Primary Root Cause | Field Remediation Action |
|---|---|---|---|---|
| E01 | PV Overvoltage | PV DC Input | Array cold-weather Voc exceeds the inverter’s 500V DC maximum PV input limit. | Measure string Voc; recalculate temperature rise; remove series panels to restore safety margin. |
| E04 | Inverter Overload | AC Output | Connected load demand exceeds continuous output capacity or the allowable surge limit of 22kVA. | Shed non-essential loads; shift heavy inductive machinery to the Smart Load output channel. |
| E08 | Grid Out of Range | AC Grid Input | Utility voltage or frequency deviated outside configured EMS tolerance bands. | Measure line AC voltage/frequency; adjust EMS grid protection windows in app if grid code permits. |
| E12 | Bus Voltage High | Inverter Internal | Energy back-feed from sudden load shedding or disconnected battery breaker during full solar generation. | Inspect battery circuit breaker and cable connections; verify BMS discharge contactor status. |
3. Battery-Side Alarm Codes: BMS Communication, Overvoltage & Thermal Cutoffs
Battery-side APP alarms originate from the internal BMS protecting Grade A LiFePO₄ cells inside wall-mounted and floor-standing mobile cabinet battery systems. The BMS continuously monitors cell voltage, temperature, current, and State of Charge (SOC), enforcing electrical and environmental protection limits to prevent cell degradation and unsafe operating conditions.
The most common battery alarm during multi-pack commissioning is BMS Communication Loss (Code B01). In a parallel battery system—such as multiple AL-WM512200 10.24kWh wall-mounted batteries or MB512300 15.0kWh floor-standing mobile cabinet batteries—the units communicate through a shared CAN or RS485 bus using a Master-Slave topology.
Engineering Tip: Parallel Battery Voltage Matching
Before closing battery circuit breakers and establishing closed-loop CAN communication with the hybrid inverter, measure the terminal voltage of each individual battery pack. All parallel packs must be matched within 0.5V DC before connection. Connecting battery packs with significant voltage differences can create high equalization currents, triggering BMS overcurrent protection and communication interruptions.
To properly establish closed-loop communication and eliminate Code B01:
- Assign battery DIP switch addresses sequentially. The battery unit connected directly to the hybrid inverter CAN/RS485 communication port must be configured as Address 1 (Master BMS). Additional parallel battery units must be configured as Address 2 through Address 6 (Slave BMS).
- Use communication cables with verified RJ45 pin definitions matching the inverter Energy Hub and battery communication ports. Standard Ethernet patch cables may use different pin assignments and cannot be assumed to support RS485 A/B or CAN_H/CAN_L communication.
- Configure the hybrid inverter battery control mode through the APP interface and change from Voltage Control (Open Loop) to the corresponding closed-loop BMS communication protocol.
Temperature-related alarms must be evaluated according to LiFePO₄ electrochemical operating limits. Charging LiFePO₄ cells below 0°C can cause lithium plating on the graphite anode, permanently reducing cell performance and increasing internal safety risks.
TEMPERATURE OPERATIONAL BOUNDARIES
Discharge Only │ Normal Operation │ Charge Cutoff
(No Charging) │ (Charge & Discharge) │
─────────────────────┼───────────────────────────────────┼────────────
-20°C / -15°C 0°C 50°C
When cell temperatures drop below 0°C during charging, the BMS triggers Code B03 (Low Temperature Charge Cutoff). Under this condition, the BMS blocks charging current while maintaining the discharge path. Wall-mounted battery systems can discharge down to -15°C, while floor-standing mobile cabinet batteries can operate down to -20°C. Charging resumes only after battery cell temperatures return above the configured charging threshold.
| APP Code | Alarm Description | System Layer | Trigger Condition | Engineering Field Resolution |
|---|---|---|---|---|
| B01 | BMS Communication Loss | Communication | Missing CAN/RS485 data frames between Master BMS and Inverter EMS. | Verify RJ45 pinout; inspect address DIP switches (Master = ID 1); confirm protocol settings in APP. |
| B03 | Low Temp Charge Cutoff | Thermal Safety | Battery temperature sensor detects cell temperature below 0°C during charging. | Inhibit PV charging attempt; relocate battery to climate-controlled room or activate battery thermal heating. |
| B05 | High Cell Voltage Cutoff | Cell Safety | Individual cell voltage exceeds 3.65V or total battery pack voltage exceeds 58.4V DC. | Perform a controlled low-current charging cycle to allow the internal passive balancing circuit to reduce cell voltage deviation. |
| B08 | Battery Under-Voltage | Capacity / DoD | Pack voltage drops below 40.0V DC or SOC reaches the configured low-voltage threshold. | Initiate generator auto-start through dry contact or apply grid AC charging to recover battery capacity. |
4. Step-by-Step Field Diagnostic & Fault Clearance Workflow
When dispatched to resolve active error codes on an off-grid solar energy storage system, technicians must follow a structured diagnostic and isolation workflow to protect personnel safety, prevent accidental electrical arcing, and avoid unnecessary hardware replacement.
[Start On-Site Diagnosis]
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[Step 1: Record APP Fault Logs & Measure Physical AC/DC Voltages]
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[Step 2: Safely Isolate System - Open AC Output/Input Breakers, then PV and Battery DC Isolators]
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[Step 3: Perform Physical & Wiring Inspections (Terminal Torque, Cable Continuity, Communication Pinouts)]
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[Step 4: Execute Cold Reset - Wait 3 Minutes for Bus Capacitors to Discharge]
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[Step 5: Sequential Re-energization - Battery ──► Inverter ──► PV ──► AC Input ──► Loads]
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[Re-commission Parameters & Clear APP Alarm Logs]
Step 1: Record Alarm Telemetry and Perform External Measurements
Document all active error codes, warning flags, and timestamped events displayed on the Solar of Things APP. Before changing system switch states, measure actual electrical parameters using calibrated instruments, including a True-RMS digital multimeter:
- Measure battery DC voltage across the positive and negative terminals to verify pack voltage status.
- Measure PV string open-circuit voltage at the IP65 DC combiner box output or inverter PV DC input terminals.
- Measure AC input line voltage and frequency from utility or generator terminals.
Step 2: System Isolation and Safety Lockout
If physical hardware work, cable re-termination, or communication inspection is required, de-energize the Solar ESS according to the following sequence:
- Open all AC output branch breakers powering downstream distribution panels.
- Open the main AC input breaker from the grid or generator supply.
- Switch off the PV DC isolators at the inverter input and combiner boxes.
- Turn off individual battery pack power switches, then open the main DC breaker between the battery bank and hybrid inverter.
Step 3: Mechanical and Wiring Integrity Inspection
Verify that all high-current terminal connections are tightened according to manufacturer specifications. 51.2V lithium battery terminals must be tightened to 12 Nm–15 Nm to prevent high-resistance heating. Inspect RJ45 communication cables for pin damage, verify IP65 DC combiner box SPD status indicators, and confirm correct battery DIP switch address configurations.
Step 4: System Reset and Bus Capacitor Discharge
When clearing latched fault codes or resetting communication states, perform a complete cold power cycle. After opening all AC and DC isolation devices, wait a minimum of 3 minutes to allow the hybrid inverter internal DC bus capacitors to discharge safely.
Step 5: Controlled Re-energization and Parameter Commissioning
Re-energize the storage platform in sequential order:
- Close the main battery DC breaker and activate battery BMS power switches. Wait for the inverter display to initialize and confirm normal startup communication.
- Verify closed-loop BMS communication status through the inverter display or Solar of Things APP interface.
- Turn on the PV DC isolators. Confirm that the MPPT tracker detects solar voltage and begins ramping up charge current.
- Close AC input breakers from the grid or generator source and verify correct AC synchronization.
- Close AC output distribution breakers to restore site loads. Clear historical alarm records in the APP interface and verify normal system operation.
5. Preventing Common Field Installation Errors Triggering APP Alarms
Many APP alarm events are caused by field installation errors or configuration mismatches rather than hardware failures. Identifying these failure modes during initial commissioning helps technicians perform accurate troubleshooting and reduce repeated service interventions.
COMMON FIELD WIRING ERRORS & FAULT TRIGGERS
[ Undersized DC Battery Cable ] ──────► Excessive Voltage Drop ──► Battery Under-Voltage Alarm (B08)
[ Incorrect Communication Cable Pinout ] ──────► CAN/RS485 Signal Failure ──► BMS Communication Loss (B01)
[ Missing Cold-Weather Voc Calculation ] ──────► PV String Voltage Rise ──► PV Overvoltage Alarm (E01)
[ Incorrect DIP Switch Addressing ] ──────► Communication Address Conflict ──► BMS Data Communication Failure (B01)
5.1 Undersized DC Battery Cables
Installing undersized battery cables between the 51.2V battery bank and hybrid inverter can introduce excessive DC voltage drop during high-power operation. For example, a 12kW inverter operating near maximum output may require more than 200A DC current depending on battery voltage and system efficiency.
If the cable cross-section is insufficient, voltage drop across the DC conductors can cause the inverter-side voltage measurement to fall below the battery protection threshold. This condition may trigger a Battery Under-Voltage alarm (Code B08) or overload protection event even when the battery pack retains available State of Charge.
5.2 Communication Cable Pinout Errors
Installers may incorrectly assume that any RJ45 cable can connect a LiFePO₄ battery to a hybrid inverter. However, standard Ethernet patch cables are designed for network communication and may not match the manufacturer-defined CAN or RS485 communication pin assignments used by battery BMS systems.
Inverter and BMS communication ports use specific RJ45 pin assignments for RS485 (A/B) or CAN (CAN_H/CAN_L) differential signals. Incorrect cable pinouts can interrupt communication frames and trigger Code B01 on the mobile monitoring interface. Communication cables must follow the manufacturer-defined wiring diagrams.
5.3 Neglecting Parallel Battery Pack Addressing
In multi-pack parallel battery installations, incorrect DIP switch addressing can create communication conflicts on the shared CAN or RS485 bus. If multiple battery packs use the same address ID, the EMS cannot correctly identify aggregated SOC, voltage, and temperature data, resulting in recurring BMS communication alarms and inaccurate APP monitoring information.
| Installation Misconfiguration | Direct Electrical Mechanism | Resulting APP Error Code | Preventive Engineering Standard |
|---|---|---|---|
| Undersized DC Power Cables | Excessive I²R cable losses and transient DC voltage drop during high-power load operation. | B08 (Under-Voltage) / E04 (Overload) | Select DC battery cables according to maximum continuous inverter current requirements while maintaining low voltage drop. |
| Incorrect RJ45 Pinouts | RS485/CAN differential communication lines connected to incorrect RJ45 pins or incompatible wiring positions. | B01 (BMS Communication Loss) | Fabricate communication cables according to exact manufacturer-defined CAN/RS485 pin assignments. |
| Duplicate DIP Switch IDs | CAN/RS485 communication address conflict between multiple battery packs. | B01 / Telemetry Refresh Timeout | Assign the Master battery pack to Address 1 and configure Slave battery packs sequentially from Address 2 to Address 6. |
| Uncalculated PV String Voc | Cold ambient temperature increases PV string open-circuit voltage beyond the inverter PV input limit. | E01 (PV Overvoltage Cutoff) | Calculate maximum string Voc using the minimum historical site temperature before installation. |
6. System Maintenance & Advanced Technical Support
Executing routine preventive maintenance reduces recurring APP alarm events, maintains battery and inverter operating reliability, and supports long-term performance of off-grid Solar ESS kits.
6.1 Recommended Routine Maintenance Schedule
- Quarterly Electrical Inspections: Inspect main DC busbars, battery terminals, inverter connections, and AC distribution breakers. Re-torque high-current connections according to manufacturer specifications to reduce contact resistance and thermal stress.
- Bi-Annual BMS Calibration: Perform a complete recharge cycle to allow the BMS passive balancing function to reduce cell voltage deviation across the 16S LiFePO₄ battery configuration.
- Semi-Annual Environmental Maintenance: Clean inverter ventilation areas, inspect cooling airflow paths, and verify IP65 combiner box enclosure integrity to reduce dust and moisture-related failures.
- Firmware Verification: Verify that the hybrid inverter EMS firmware and communication gateway software versions are updated according to the latest available firmware release through supported remote update functions.
+-----------------------------------------------------------------------------------+ | PREVENTIVE MAINTENANCE CHECKLIST | +-----------------------------------------------------------------------------------+ | [ ] Quarterly: Re-torque battery & inverter DC power terminals (12–15 Nm). | | [ ] Quarterly: Verify IP65 DC combiner box surge protection devices (SPDs). | | [ ] Bi-Annual: Perform a complete recharge cycle to support BMS passive cell | | balancing. | | [ ] Semi-Annual: Clean inverter heat-sink cooling fins and air intake filters. | | [ ] Semi-Annual: Inspect communication wiring continuity and CAN/RS485 RJ45 | | connections. | | [ ] Annual: Update inverter EMS & APP gateway firmware via supported update | | functions. | +-----------------------------------------------------------------------------------+
For complex installations, including multi-inverter parallel systems up to 6 units, hybrid microgrids with generator auto-start through dry contact control, and customized off-grid projects, professional engineering support helps validate system configuration and improve long-term operational reliability.
6.2 Customized B2B Engineering Support
Haven Deer provides B2B engineering support for electrical contractors, EPC integrators, and solar distributors. The engineering team assists with:
- Complete single-line diagram (SLD) reviews and pre-commissioning validation.
- Customized string sizing and temperature coefficient calculations for extreme climate deployments.
- Customized BMS/EMS integration support for specialized OEM/ODM energy storage applications.
- On-site or remote advanced diagnostic support for multi-unit parallel system architectures.
7. Frequently Asked Questions
1. How do I fix a BMS communication error (B01) on the Solar of Things APP?
Verify the physical communication connection between the battery bank Master BMS and the hybrid inverter. Ensure that the communication cable follows the manufacturer-defined CAN or RS485 pinout. Confirm that the Master battery is configured as Address 1, Slave batteries are assigned sequential addresses from 2 to 6, and the inverter battery protocol setting matches the selected BMS communication protocol.
2. Why does my app show a PV Overvoltage alarm on cold winter mornings?
Solar modules exhibit a negative temperature coefficient, meaning their open-circuit voltage (Voc) increases as module temperature decreases. If PV string sizing does not consider the minimum site temperature, the cold-weather string Voc may exceed the inverter’s maximum PV input limit of 500V DC. Recalculate the string configuration and reduce the number of series-connected modules to restore a safe voltage margin.
3. What should I do if the battery shows a Low Temperature Charge Cutoff alarm?
LiFePO₄ battery cells should not be charged when cell temperatures are below 0°C because lithium plating may occur on the anode surface. The BMS automatically blocks charging current while maintaining discharge operation. Move the battery modules to a temperature-controlled installation environment or activate battery heating functions to resume charging.
4. Why is the backup generator failing to start automatically when a low battery alarm appears?
First, verify that the passive dry contact signal wiring is correctly connected between the inverter dry contact port and the generator remote auto-start controller. Then check the inverter EMS settings to confirm that the generator start trigger conditions, such as SOC percentage or battery voltage thresholds, are correctly configured.
5. How do I clear persistent error codes after resolving the underlying physical fault?
After resolving the physical fault, clear historical alarm records through the Solar of Things APP interface. If the alarm remains latched, perform a complete cold reset by opening AC and DC isolation devices, waiting 3 minutes for inverter DC bus capacitors to discharge, and restoring power in the sequence of battery, inverter, PV, and AC sources.
6. What causes an AC Output Overload alarm during heavy motor startup?
Inductive loads such as water pumps, compressors, and air-conditioning systems can draw short-duration startup currents several times higher than their normal running current. If the startup surge exceeds the inverter surge capability, such as 22kVA for 5 seconds on the 12kW model, the inverter activates overload protection to protect its power electronics. Move non-critical inductive loads to the Smart Load output channel where applicable.
7. Can I operate the hybrid inverter if BMS communication is lost completely?
If BMS communication cannot be restored immediately, the inverter can be temporarily switched from Closed-Loop BMS mode to Open-Loop Voltage Control mode for emergency operation. Configure charging voltage, float voltage, and low-voltage protection parameters according to the battery specifications until CAN or RS485 communication is restored.
8. Why does the APP show “Grid Frequency Out of Bounds” when running on generator power?
Small or unstable generators may experience frequency fluctuations when electrical loads change, causing the AC input frequency to exceed the inverter acceptance range. Check generator output frequency and adjust the inverter AC input acceptance parameters according to the generator operating characteristics.
9. What is the difference between a BMS Alarm and an Inverter Fault?
A BMS alarm originates from the battery management system and protects LiFePO₄ cells against abnormal voltage, current, temperature, and safety conditions. An inverter fault originates from the hybrid inverter power conversion system and indicates issues related to PV input, AC output, grid/generator interface, or internal protection functions.
10. How many battery packs can communicate in parallel without causing bus congestion errors on the app?
For standard 51.2V wall-mounted and floor-standing mobile cabinet energy storage systems, up to 6 battery packs can be connected in parallel while maintaining stable CAN/RS485 communication and reliable APP telemetry aggregation.
8. Contact Us for a Customized Solution
Need assistance with off-grid Solar ESS system sizing, field troubleshooting, or customized OEM/ODM energy storage integration? Contact Haven Deer’s engineering team for single-line diagram reviews, system configuration validation, battery and inverter matching, and tailored Solar ESS Kit solutions.