EcoFlow DELTA Pro 3 Error ERR-304: High-Voltage Solar Overvoltage Lockout
Error ERR-304 triggers when open-circuit voltage (Voc) on the high-voltage PV port exceeds the hardware threshold of 150V DC (often exacerbated by low temperature coefficients), causing the MPPT controller to latch shut to protect internal DC bus capacitors and buck-boost MOSFETs.
Hardware Diagnostic Matrix
Spec Ref #b3ff1b5dRequired Diagnostic Tools & Instrumentation
Multimeter Probing Targets & Circuit Tolerances
Bench Calibrated ±5%| Test Point / Circuit | Target Nominal Spec | Expected State | Fault Condition |
|---|---|---|---|
| Main Logic DC Bus | 3.3V / 5.0V DC (±0.1V) | Stable DC Potential | <2.9V (Brownout / Sag) |
| Thermistor / NTC Sensor | 10kΩ - 100kΩ @ 25°C | Smooth Thermal Curve | 0Ω (Short) or ∞ (Open) |
| Safety Ground / PE Continuity | < 0.5Ω Resistance | Solid Earth Bond | > 1.0Ω (Floating Chassis) |
Common Symptoms & Fault Manifestations
- LCD panel flashes ERR-304 accompanied by continuous warning beeps
- Solar charging immediately ceases; input wattage displays 0W
- High-voltage solar icon blinks red or remains grayed out in EcoFlow App
Root Causes & System Failure Modes
Solar array open-circuit voltage (Voc) exceeds the absolute maximum 150V DC limit under cold ambient conditions
String configuration error (too many PV modules connected in series instead of series-parallel)
Short-circuit or reverse polarity surge triggering internal MPPT protection latch
Degraded or shorted input surge suppression varistor (MOV) or overvoltage sensing comparator circuit
High-Voltage & Mechanical Safety Isolation
Prior to opening access panels, disconnecting terminals, or probing wiring, perform complete lock-out / tag-out (LOTO). Disconnect all AC mains, DC string isolators, and lithium battery banks. Allow internal smoothing capacitors at least 3 to 5 minutes to dissipate stored residual energy below safe threshold (<30VDC).
Step-by-Step Diagnostic & Resolution Procedure
Immediate Solar Disconnection & Isolation
Immediately disconnect the solar array from the DELTA Pro 3 high-voltage input port using MC4 disconnect tools. Do not unplug under active heavy load without isolating array breakers first to avoid DC arcing.
Open-Circuit Voltage (Voc) Multimeter Verification
Set the CAT III multimeter to DC voltage. Measure open-circuit voltage directly at the disconnected MC4 lead ends in full sunlight. Verify Voc is strictly below 140V DC (factoring in cold weather Voc margin; panels must not exceed 150V DC even at peak cold temperatures).
Array Reconfiguration & Polarity Inspection
If measured Voc exceeds 145V-150V, reconfigure the PV array wiring by reducing series count and converting to series-parallel. Verify positive and negative terminal orientation using the multimeter before reconnecting.
Hardware Discharge, Clear Lockout & Commissioning
Power down the DELTA Pro 3 completely. Leave unit disconnected for 10 minutes to allow DC bus capacitors to discharge. Reconnect the within-spec PV array (<140V Voc) and power on the station to confirm ERR-304 clears and MPPT tracking resumes.
Hardware Reset & Fault Clear Sequence
Controller ProcedurePrevention & Routine Maintenance Guidelines
- Calculate string Voc using the panel temperature coefficient at record low local winter temperatures to ensure total Voc never crosses 145V DC.
- Avoid daisy-chaining mismatched wattage or irregular VOC solar panels on the high-voltage MPPT port.
Frequently Asked Diagnostic Questions
What does error code ERR-304 indicate on EcoFlow DELTA Pro 3?
Error ERR-304 triggers when open-circuit voltage (Voc) on the high-voltage PV port exceeds the hardware threshold of 150V DC (often exacerbated by low temperature coefficients), causing the MPPT controller to latch shut to protect internal DC bus capacitors and buck-boost MOSFETs. In engineering telemetry, it indicates high-voltage solar overvoltage lockout requiring circuit verification.
What are the primary triggers causing error ERR-304?
Diagnostic bench telemetry isolates the following common root causes: Solar array open-circuit voltage (Voc) exceeds the absolute maximum 150V DC limit under cold ambient conditions; String configuration error (too many PV modules connected in series instead of series-parallel); Short-circuit or reverse polarity surge triggering internal MPPT protection latch; Degraded or shorted input surge suppression varistor (MOV) or overvoltage sensing comparator circuit.
How do I reset and clear EcoFlow error ERR-304?
Disconnect all AC and DC inputs. Press and hold the main power button for 10-15 seconds until the display turns off completely. Wait 5 minutes for bus discharge, then power on without solar attached. Reconnect verified DC input. If the error status repeats immediately after clearing, discontinue clearing and test circuit continuity.
Can I safely resolve error ERR-304 without specialized shop tooling?
This fault is graded as Intermediate difficulty with Critical severity. Standard diagnostics require an insulated digital multimeter and appropriate hand tools. Always observe high-voltage isolation procedures.