Battery Troubleshooting

Only batteries from the official compatible battery list can be used in closed-loop. Please see this article for more details about batteries: https://usservice.solisinverters.com/en/support/solutions/articles/73000669626-compatible-batteries-non-compatible-batteries-low-voltage-hybrids-only-

Going forward in this article, the assumption is that you have installed one of the officially approved compatible batteries. If you are using a battery that is not on this list, then this guide will not help. 

There are several different alarms that can indicate a specific problem with the battery. However, not all battery issues show themselves with an alarm. Some issues are due to communication.

If after performing the troubleshooting steps outlined below the issue persists, please contact Solis support usservice@solisinverters.com (866)438-8408 option 2. 

Common Battery-Related Alarms

• NO-Battery: The inverter senses 0V on the DC battery terminals. This is a hardware/wiring issue, not a communication issue. 
• Batt_Comm_FAIL: The inverse of NO-Battery, the inverter measures voltage on the DC battery terminals but the communication is abnormal.
• UN-Vbatt: The inverter measures the battery as abnormally low voltage
• OV-Vbatt: The inverter measures the battery as abnormally high voltgae
• Alarm-BMS: The BMS is reporting an alarm. Check the BMS using the battery’s app.

NO-Battery alarm

The inverter is seeing 0V on the battery DC terminals.

1. Measure Voltage: Use a multimeter at the inverter’s DC terminals. It must be between 42V and 58V.

2. Check Breakers: Ensure the battery’s internal breaker and any external DC disconnects are closed.

3. Wake up the BMS: If the battery is deeply discharged, the BMS may be in "Sleep Mode." Most batteries have a "Start" or "Reset" button to jump-start the pre-charge circuit.

4. Polarity: Double-check that BATT+ and BATT− are not swapped.

Batt_Comm_FAIL alarm

This alarm occurs when the inverter sees battery voltage but is not getting good comms with the battery. 

1. Pinout Verification: Solis uses the standard CAN pinout:

   • Pin 4: CAN_H

   • Pin 5: CAN_L

2. Cable Quality: Use a shielded CAT5e/6 cable. Avoid unshielded cables, as high-frequency noise from the inverter’s switching can interrupt the data.

3. BMS CAN Port: Ensure the pinout matches the Solis hybrid and if it does not then you will need to make a custom cable to ensure the CAN_H and CAN_L pins align. 

4. Battery Addressing:

   • For parallel battery stacks, ensure the "Master" battery is set to Address 1 (or 0, depending on the brand).

   • The CAN cable from the inverter must plug into the Master battery's "Link Port 0" or "CAN" port.

5. Configuration 

   1. Battery Select: Go to Settings → Battery Select → Lithium Battery LV (Note: do not use the one that has “RS485” in the name) or if the battery uses Pylontech protocol then select Pylon_LV

6. Update the BMS: If the battery is a newer model, ensure its firmware is updated

7. Update the Inverter: Update the inverter firmware using the SolisCloud app connected to the inverter through Bluetooth, instructions can be found here: https://usservice.solisinverters.com/en/support/solutions/articles/73000661258-upgrading-solis-hybrid-inverter-firmware-locally

8. Hard Reset: 

   1. Turn OFF: AC Breaker → PV Switch → Battery Breaker.

   2. Wait 5 minutes for the screen to go completely dark.

   3. Turn ON: Battery first, then AC, then PV

9. Check:

   1. Does the alarm persist? If yes, check the Battery icon on the overview of the plant. Does it show an SOC%? If it does show an SOC% but you still have the alarm, it is a protocol mismatch. If it does not show any SOC% then it is likely a wiring issue. 

   2. The wiring is confirmed to be good but the issue persists then it is most likely a protocol issue. Try changing the battery selected to another type, either Pylontech or Pytes, something else. After that, see if you now have different information coming from the battery. If nothing changes, please contact Solis support.

UN-Vbatt alarm

This occurs when the battery voltage drops below the inverter’s operational cutoff (typically 40V–42V) or the BMS's internal protection threshold.

1. Direct Voltage Measurement: Use a multimeter to measure at the inverter DC terminals. If the reading is below 40V, the inverter will not "see" the battery and will not initiate a charge.
2. BMS "Wake-Up": Most closed-loop batteries (like Pylontech or Pytes) have a "Start" or "Reset" button. Press and hold this to trigger the pre-charge circuit. This should temporarily provide enough voltage for the inverter to detect the DC bus.
3. Manual Charge: If the BMS is active but the voltage is too low for normal operation, navigate to System Settings → Storage Mode → Charge/Discharge Schedule. Manually set a charge window to trigger a charge from the PV or Grid to bring the cells back to a healthy state.
4. Check Discharge Depth (DOD): Ensure the Battery settings are not set too low. Increasing the Force Charge, Recover, and Over Discharge SOC% can prevent repeat undervoltage events during periods of low solar production. It is recommended to keep the Overdischarge between 15% and 20% and then to keep the Force Charge between 10% and 15%. The recovery should be 1-2% more than the Force Charge SOC%.

OV-Vbatt alarm

Overvoltage usually indicates that the inverter is pushing current into a battery that is already full or has a cell imbalance.

1. Check Charge Setpoints: In Battery Select → User-Defined (if not using closed-loop), verify that the Charge Limit Voltage is not set higher than the battery manufacturer's maximum (usually 56V–58.4V).

2. BMS Handshake Calibration: In closed-loop mode, the BMS dictates the charge voltage. If the inverter overshoots this, there may be a firmware lag. Perform a Full Power Cycle (Battery → AC → PV) to resync the communication.

3. Cell Imbalance Check: If the total pack voltage looks normal (e.g., 54V) but you still get an OV alarm, one internal cell may be spiking. Check the battery’s internal software/app or LED indicators.

4. Reduce Charge Amperage: Temporarily lower the Max Charge Current (e.g., from 100A to 50A) in the inverter settings. This allows the BMS more time to balance the cells via its internal resistors without hitting the high-voltage cutoff.

Alarm-BMS alarm

This alarm indicates that the communication link is healthy, but the battery is reporting an internal hardware or environmental issue.

• Environmental Scan: Most BMS faults are triggered by Temperature. Ensure the battery room is between 10°C and 40°C. Lithium batteries will often trigger a "BMS Stop Charge" if they are below freezing.

• Diagnostic LED Codes: Refer to the battery’s manual to decode the LED flash pattern (e.g., "ALM" light blinking 3 times). This usually points to:

  • Over-current protection

  • Short circuit

  • MOSFET failure

• Clear the Fault Buffer: Turn off the battery’s DC breaker and logic switch. Wait 60 seconds for the internal BMS capacitors to discharge, then restart.

• Isolation Test: If you have multiple battery modules in parallel, disconnect them and test each module individually with the inverter. This identifies if a single faulty module is poisoning the entire CAN bus string.