Solar Battery Not Charging — 7 Common Causes and Fixes
A battery that stops charging means lost self-consumption, no backup power, and wasted solar energy. Before calling a technician, work through these seven common causes — most can be resolved in minutes.
1. Battery Type Not Set Correctly
The most common cause. If your Deye inverter is set to "No Battery" or the wrong battery type, it will not charge. Go to Settings > Battery Type in the inverter menu or SolarMan app and select "Lithium" for LiFePO4 batteries.
2. CAN Communication Cable Disconnected
The CAN cable carries BMS data between the battery and inverter. If disconnected or damaged, the inverter sees no battery. Check both ends of the CAN cable are firmly seated. Look for error code W03 on the inverter display.
3. Battery BMS Protection Active
The Battery Management System may have triggered protection due to over-temperature, over-voltage, or cell imbalance. Check the battery LED indicators. Most BMS protections reset automatically once conditions normalise. If not, power cycle the battery by disconnecting for 30 seconds.
4. Insufficient Solar Production
The battery only charges when solar production exceeds home consumption. On cloudy days or with heavily shaded panels, there may be no surplus power. Check the SolarMan app — if solar production is lower than consumption, the battery will not charge from solar alone.
5. Time-of-Use Settings Blocking Charge
If you have configured time-of-use scheduling, the inverter may be programmed not to charge during certain hours. Check Settings > Work Mode > Time of Use in the SolarMan app and verify your charge windows are correct.
6. DC Battery Breaker Tripped
A tripped breaker between the battery and inverter physically disconnects the battery. Check the DC breaker near the battery and reset if tripped. If it trips repeatedly, there may be a wiring fault — call an electrician.
7. Battery End of Life
If your battery is old (6+ years for gel, 15+ years for LiFePO4), it may have reached end of life and can no longer accept charge. Check the battery's State of Health (SOH) in the SolarMan app. Below 60% SOH indicates replacement is needed.
Quick Diagnostic Checklist
- Check inverter display for error codes (especially W03, W05)
- Verify battery type is correctly set in inverter
- Check CAN cable connections at both ends
- Check battery LED indicators for BMS protection status
- Verify DC battery breaker is on
- Check solar production vs consumption in SolarMan app
- Review time-of-use schedule settings
Frequently Asked Questions
Why is my solar battery not charging?
The top causes are: wrong battery type setting in the inverter (most common), disconnected CAN communication cable, BMS protection triggered, insufficient solar production, or time-of-use settings blocking charge. Start by checking the battery type setting in your Deye inverter menu.
What does error W03 mean for battery charging?
W03 means the inverter has lost communication with the battery's BMS via the CAN cable. Without BMS communication, the inverter will not charge the battery for safety reasons. Check that the CAN cable is securely connected at both the battery and inverter ends.
How do I check if my solar battery needs replacement?
Check State of Health (SOH) in the SolarMan app under battery details. Above 80% SOH is healthy. Between 60-80% shows degradation but is still functional. Below 60% SOH means the battery should be replaced. LiFePO4 batteries typically stay above 80% for 10+ years.
