Understanding AC-Coupled Batteries
AC vs DC Coupled Battery Systems
DC-Coupled System
In a DC-coupled setup:
Solar panels generate DC electricity → this DC power directly charges the battery → then it is converted to AC by a hybrid inverter for use in the home or export to the grid.
AC-Coupled System
In an AC-coupled setup:
Solar panels generate DC electricity → a solar inverter converts this to AC → the AC electricity is used by the household and/or sent to a battery inverter, which re-converts AC to DC to charge the battery.
How to Know if Your AC-Coupled Battery Is Working
A simple way to check if your AC-coupled battery system is functioning correctly is to observe its behavior throughout the day:
-
In the morning and afternoon: the battery should be charging, as solar production is available.
-
At night: the battery should be discharging, providing power to the home when solar is no longer available.
If you see this pattern, charging during the day and discharging at night then your battery system is doing its job.
How Power Flow Monitoring Works
Accurate load calculation in a solar-plus-storage system depends on the inverter’s ability to monitor three key data points:
-
Solar Production – the amount of power generated by the solar panels.
-
Battery Power – positive when discharging, negative when charging.
-
Grid Power – positive when importing power from the grid, negative when exporting.
By using these three values, the inverter can determine the actual load (i.e., how much power is being consumed by the home or site):
Load = Solar Power + Battery Power + Grid Power
Example 1:
-
Solar: 3000 W
-
Battery: -2000 W (charging)
Grid: 0 W
→ Load = 3000 - 2000 + 0 = 1000 W
Example 2:
-
Solar: 3000 W
-
Battery: 0 W (fully charged)
Grid: 2000 W (importing)
→ Load = 3000 + 0 + 2000 = 5000 W
Example 3:
-
Solar: 6000 W
-
Battery: -2000 W (charging)
Grid: -1000 W (exporting)
→ Load = 6000 - 2000 - 1000 = 3000 W
Related Articles
Understanding Battery Cell Imbalance
Battery banks configured in parallel are common in solar energy storage systems. While parallel configurations increase amp-hour (Ah) capacity and enable higher energy reserves at a constant voltage, they also introduce a critical challenge: State of ...Managed vs Unmanaged Batteries and How SOC Works
State of Charge (SOC) indicates the remaining capacity of a battery as a percentage. How SOC is calculated and reported depends on whether the battery is managed or unmanaged. Managed Batteries: Examples: BSL, Pylontech, Sungrow These batteries ...Pylontech Battery - Basic Troubleshooting Guide (Batteries not discharging - Battery Monitor [512] Internal Failure Alarm)
Once this is reported by the customer, we must first request for photos of the whole setup to check any wiring/connection anomalies. Then confirm the number of affected batteries by following the steps below 1: On the VRM portal, Go to Remote Console ...Does discharging a BSL battery to 5% affect performance and warranty?
Discharging a BSL battery down to 5% won’t harm its performance or void the warranty. These batteries are built to handle deep discharges, meaning you can safely use up to 95% of the battery’s total capacity before charging again. This makes BSL ...Pylontech Battery – Basic Troubleshooting Guide
This guide outlines the correct wiring, startup, and shutdown procedures for integrating Pylontech US5000 lithium batteries with a Victron inverter system via CAN-bus communication. It is compatible with Victron and Deye hybrid inverters. Quick Check ...