A normal battery voltage does not prove that a battery can accept or deliver current. The BMS may have disabled charging, discharging, or both. The inverter may also be holding the system in standby because of SOC limits, operating schedules, a missing battery profile, or incomplete communication.
For an installer, the fastest route is to classify the symptom first, then read the BMS permissions and limits before replacing a battery or communication cable. This decision tree separates a blocked operating command from a protection event, a communication problem, and a physical DC-path fault.
Start with the exact symptom
“The battery will not work” is not enough information for a supplier or technical team. Record what the inverter sees, what the BMS reports, and whether charging and discharging fail in the same way.
| Observed condition | First diagnostic direction | Do not assume |
|---|---|---|
| Battery is not visible in the inverter | Wake state, communication, address, cable, port, or BMS status | That the battery is empty or permanently damaged |
| Battery is visible but charge current is 0 A / 0 W | Charge permission, charge-current limit, SOC, temperature, or inverter control | That normal terminal voltage means charging is allowed |
| Battery is visible but discharge is blocked | Discharge permission, discharge-current limit, minimum SOC, or over-discharge protection | That the inverter has a power-stage failure |
| Both charge and discharge are blocked | BMS protection, contactor/wake state, communication, or a DC-path fault | That replacing the battery is the next step |
| Current starts and then falls | Cell balance, temperature, CCL/DCL, communication, or cable voltage drop | That this is the same as an immediate block |
If current starts and then falls after the system has operated for a period, use CVC’s guide to battery charging power drop after 20 minutes. This article focuses on a system that is blocked or appears blocked at the start of the test.
Check BMS permission and limits first
The BMS is the first place to look because it can keep the pack voltage within a normal-looking range while preventing current from flowing. A protection flag, a sleeping contactor, or a zero current limit can all produce a “normal voltage, no charge or discharge” symptom.
Ask for a BMS screenshot or export that shows:
- Charge Enable and Discharge Enable;
- maximum charge current and maximum discharge current;
- SOC and the configured SOC limits;
- highest and lowest cell voltage;
- cell voltage difference;
- highest and lowest temperature;
- active protection, alarm, or event status;
- contactor, wake, or system-ready status.
Do not insert generic voltage or temperature thresholds into a cross-brand article. The correct limits depend on the exact battery model, BMS revision, chemistry, firmware, and operating conditions. Use the product manual or supplier record for the selected model.
Separate BMS protection from inverter control
If the BMS shows that charge and discharge are permitted, look at the inverter’s operating state. The inverter can block current even when the battery is online and its DC voltage looks normal.
Record the following inverter settings and screens:
- battery type or battery profile;
- minimum SOC and backup reserve;
- charge and discharge time windows;
- maximum charge and discharge current;
- operating mode, such as backup, self-consumption, or standby;
- grid, PV, and generator operating state;
- any active warning or event code;
- the last parameter or firmware change.
A scheduled charge window can look like a failed battery. A high reserve SOC can look like a blocked discharge. A missing or incorrect battery profile can leave the battery visible but prevent the inverter from using the BMS limits correctly.
For brand-specific Deye or Growatt cases, link the reader to CVC’s Deye and Growatt battery-not-charging guide. The present article stays model-agnostic so it can be used before a specific inverter family has been selected.
Treat communication as a data path, not a port label
CAN, RS485, and an RJ45 connector describe an interface or physical connection. They do not, by themselves, confirm that the battery and inverter understand the same BMS data.
When communication is suspected, record:
- exact battery and inverter models;
- active battery port and inverter port;
- cable type and both-side pinout;
- CAN bitrate or RS485 baud rate and serial settings;
- device address and master/slave arrangement;
- BMS protocol or approved battery profile;
- battery and inverter firmware versions;
- the communication alarm and the time it appeared.
If the battery shows voltage but the inverter reports no battery data, do not start by swapping random cables. Compare both manuals and use the documented pinout. CVC’s CAN vs RS485 communication checklist covers the interface-level records in more detail.
Check the DC path within the safe boundary
Once BMS permission, inverter control, and communication have been reviewed, check whether the DC path is actually closed. A voltage reading at the battery terminals can be normal while a breaker, fuse, isolator, connector, contactor, or cable connection prevents current from reaching the inverter.
Within the procedure allowed by the product manual, confirm:
- the battery breaker, fuse, and isolator state;
- whether the inverter sees the battery voltage expected for the selected system;
- whether the battery-side and inverter-side readings are consistent;
- whether the cable and terminals show visible damage, looseness, or overheating;
- whether the event began after installation, transport, maintenance, or a wiring change.
Opening the cabinet, testing live high-current paths, replacing a fuse or contactor, and measuring inside the battery are professional service tasks. The article should help an installer prepare evidence, not encourage a customer to repair a battery.
Use the timeline to find the first change
The first useful question is often not “what is wrong now?” but “what changed immediately before the block appeared?” Build a short event timeline:
| Timeline point | Record |
|---|---|
| Before the fault | Last known charge/discharge state, SOC, temperature, and displayed battery status |
| Recent change | New inverter, new battery, firmware update, cable change, parameter change, or grid event |
| First symptom | Time, direction affected, current reading, alarm, and whether the battery remained visible |
| After a restart | What returned, what stayed blocked, and whether the symptom changed |
| Current evidence | BMS permissions, limits, cell data, temperature, inverter settings, and event logs |
A new firmware version points the review toward protocol or configuration. A low-temperature event points toward an operating boundary. A fault that follows a cable or inverter replacement points toward the integration record. The timeline does not prove the root cause, but it prevents random part replacement.
What to send the supplier before remote troubleshooting
A supplier can work much faster when the first message contains a complete evidence packet rather than a sentence saying “the battery has voltage but does not work.” Send:
- battery brand, exact model, serial number, and quantity;
- inverter brand, exact model, firmware, and quantity;
- system voltage and battery connection layout;
- photos or screenshots of the BMS and inverter status pages;
- Charge Enable, Discharge Enable, CCL, and DCL values;
- SOC, cell voltage range, cell difference, and temperatures;
- active alarms and event logs with timestamps;
- battery-terminal and inverter-terminal voltage, where safe and documented;
- CAN/RS485 port, cable, protocol, address, and firmware records;
- the recent-change timeline and the exact charge/discharge behavior;
- project country, grid type, and whether PV, generator, or backup loads are connected.
This is also the minimum information CVC needs to distinguish a product-matching question from a service fault. It connects the field symptom to a specific battery, inverter, configuration, and supplier document.
When normal voltage does not mean a dead battery
| Evidence combination | Reasonable next action |
|---|---|
| Normal voltage + BMS charge disabled | Find the protection or permission reason in the BMS log; do not label the battery dead |
| Normal voltage + BMS limits are zero | Check SOC, temperature, cell data, protection state, and supplier recovery procedure |
| Normal voltage + inverter has no usable battery data | Review profile, protocol, pinout, address, and firmware as one compatibility record |
| Normal voltage + inverter settings block the requested direction | Compare mode, reserve SOC, schedule, and current limits with the project requirement |
| Normal voltage + end-to-end DC path is abnormal | Stop customer-level troubleshooting and escalate to qualified service personnel |
A battery should be called defective only after the documented electrical, BMS, communication, configuration, and service checks support that conclusion. “Voltage is normal” is one observation, not a complete health test.
How CVC can help with product matching and the evidence pack
CVC works with distributors, importers, installers, and project buyers to organize the supply-side information behind a battery–inverter decision. That can include:
- matching the battery and inverter model combination;
- checking voltage, current, BMS protocol, and firmware records;
- requesting the correct pinout, compatibility list, and operating manual;
- organizing sample commissioning and acceptance documents;
- coordinating questions with the selected factory or supplier;
- comparing battery, inverter, and all-in-one system options for the target project.
For broader system matching, see the battery and inverter compatibility checklist. For technical documents and product files, use the CVC Downloads page.
Buyer FAQ
Does normal battery voltage prove that the battery is healthy?
No. It proves that voltage is present at the measurement point. It does not prove that the BMS allows current, that cells are balanced, that the contactor is closed, or that the inverter can use the battery data.
Why can a battery discharge but not charge?
Charge and discharge permissions are separate. The BMS may block charging because of a high-cell-voltage, temperature, SOC, or charge-limit condition while leaving discharge available. Check the model-specific BMS status and event log.
Why can a battery charge but not discharge?
The inverse can happen when the minimum SOC, discharge current limit, over-discharge protection, or inverter reserve setting blocks discharge. Confirm both the BMS DCL and the inverter’s operating settings.
Should I replace the CAN or RS485 cable first?
Not automatically. First compare the battery-side and inverter-side pinouts, protocol, settings, address, and firmware. An RJ45 plug can fit while its signal assignment is wrong.
Can a restart clear the problem?
A restart may clear a documented temporary state, but it does not fix an incompatible protocol, an active protection condition, a wrong reserve setting, or a damaged DC path. Record the status before and after the restart.
The diagnostic record should follow the quotation
When battery voltage is normal but charging or discharging is blocked, start with the state of the system, not the name of a replacement part. Classify the symptom. Read BMS permission and limits. Check inverter control. Confirm communication as a complete data path. Then review the DC path and escalate unsafe work.
The same record should follow the project from RFQ to sample commissioning and after-sales support. Send CVC the battery model, inverter model, target country, exact behavior, and available BMS data. We can help identify whether the next step is compatibility review, supplier evidence collection, or qualified technical service.
Peter Yin
Request a Battery–Inverter Diagnostic Review
Send the battery model, inverter model, target country, exact charge/discharge behavior, BMS data, and available communication records. CVC can help organize the matching and supplier evidence needed for the next step.