Battery Not Charging On New Install Commissioning Mode vs SOC Cap vs Comm Decision Tree

Why this matters

A brand-new energy storage system that will not charge is almost always a configuration or communication problem, not a dead battery. The three dominant causes at commissioning are: the system is still in a commissioning or standby mode and has not been told to operate, a state-of-charge (SOC) or charge-current limit is set such that the system thinks it is already full or is throttled to zero, or the battery management system (BMS) and the inverter/charger are not talking and the charger refuses to source current without BMS authorization. Working the tree in the right order keeps you from RMA-ing a perfectly good battery because a comm cable was on the wrong port.

Symptom presentation

• Battery SOC sits at the same value, neither rising nor falling, with PV available points at commissioning mode or a charge limit.
• Inverter shows the battery online but charge power reads zero points at SOC cap, a charge-current limit, or a comm handshake that allows monitoring but not charging.
• Inverter shows no battery or a comm/BMS fault points at communication wiring, protocol mismatch, or address/termination errors.
• Battery breaker/contactor open or a BMS alarm latched points at a protection event (over/under temperature, cell imbalance, transit-disconnect) blocking charge.

Quick checks

1. Read every fault and status code on both the inverter/charger and the battery/BMS. New installs frequently show a transit or shipping disconnect, a "press to wake" requirement, or a low-temperature charge inhibit.
2. Confirm the battery DC disconnect/breaker is closed and the precharge/contactor has engaged. Measure DC voltage at the inverter battery terminals and compare to pack voltage; a large delta means an open path.
3. Verify the configured battery model/profile in the inverter matches the installed battery exactly. A wrong profile sets wrong voltage and current limits.
4. Check the operating mode. Many systems ship in standby or require a commissioning step (firmware update, time/date set, grid-code selection) before they enable charge/discharge.

Isolation tree

Step 1: Is there an active BMS protection alarm? Yes (over/under temp, cell imbalance, over/under voltage, contactor open): this is a protection event, not a setup miss. Cold batteries commonly inhibit charge below a threshold; warm the space or wait. Cell imbalance on a new pack may need a balancing/conditioning cycle per the manufacturer. Resolve the alarm before anything else. No active alarm goes to Step 2.

Step 2: Does the inverter see the battery at all (comm established)? No battery seen, or a comm/BMS-loss fault, goes to the communication branch (Step 5). Battery seen and online goes to Step 3.

Step 3: Is the system out of standby/commissioning mode and set to charge? Confirm the operating mode is active (not standby, not commissioning-incomplete), that required commissioning steps are done (grid code, firmware, region), and that the work mode actually permits grid/PV charging in the current schedule. Many systems will not charge from the grid unless explicitly allowed, and will not charge from PV if PV is below threshold. Fix the mode/schedule and re-check. If mode is correct, go to Step 4.

Step 4: Are SOC or current limits blocking charge? Check the configured max-SOC/charge-SOC cap; if it is set at or below current SOC, the system considers itself full. Check the max charge current limit; if it is zero or very low (sometimes defaulted that way pending BMS-reported limits), no meaningful charge flows. Also confirm the BMS-reported charge-current limit is non-zero; the BMS can command zero charge current during balancing or temperature events. Correct the limit, re-check, and confirm charge power climbs.

Step 5 (communication branch): Verify the BMS-to-inverter link.

• Confirm the comm protocol/baud and the selected battery brand match on the inverter side.
• Verify the cable is on the correct port (CAN vs RS-485 are easy to swap), pinout is correct, and CAN bus termination is set per spec (resistor or DIP switch).
• Confirm battery address/ID and, on multi-module stacks, the master/slave addressing and inter-module links.
• Power-cycle in the manufacturer's prescribed order (often battery first, then inverter) after wiring corrections; comm handshakes frequently establish only on a clean boot.

Confirming diagnosis

• Commissioning/mode confirmed when completing the commissioning steps or leaving standby makes charge power go positive with no other change.
• SOC/current cap confirmed when raising the SOC cap or the charge-current limit immediately produces charge current.
• Communication fault confirmed when correcting protocol/port/termination/address and rebooting clears the comm fault and the inverter begins reporting live BMS data and charging.
• BMS protection confirmed when the alarm (temperature, balance) clears and charge resumes once conditions return to the allowed window.

Remediation

• Complete all commissioning steps; set operating mode and schedule to permit PV/grid charging.
• Match the battery profile in the inverter to the installed model; set SOC and current limits to manufacturer defaults, not zero.
• Correct comm protocol selection, cable port/pinout, termination, and addressing; reboot in the specified order.
• For protection events, restore temperature window, allow initial balancing per the manufacturer, and clear the transit/shipping disconnect.

References

• NEC (NFPA 70) Article 706, Energy Storage Systems
• UL 1741, Inverters, Converters, Controllers and Interconnection System Equipment
• NEC (NFPA 70) Article 690.71, Energy Storage Systems (interconnection)
• IEC 62446-1, Photovoltaic (PV) systems - Requirements for testing, documentation and maintenance