Quick answer
Get the exact battery, inverter, controller and firmware details and ask the EMS supplier to check them. The EMS must be able to read the right live data and send charge and discharge commands back to the inverter. A Modbus port or matching brand name alone does not prove it will work.
Start by getting the exact model numbers for the inverter, battery, battery management system, or BMS, and controller at the client’s premises.
Ask the EMS supplier to confirm that the EMS can:
- Read the data it needs from the existing equipment
- Send charging and discharging instructions to the inverter
Then ask the EMS supplier to test what the inverter and battery do if the controller loses contact with the inverter or the internet connection fails.
Do not treat a matching brand name, Ethernet port, or Modbus connection as proof that the EMS can control the battery.
What do we need to check on the inverter and controller?
Check the exact equipment, the connection that the EMS will use to exchange data and instructions, and which controller the inverter follows if more than one controller sends instructions.
Start by recording the make and model of the:
- Battery and BMS
- Inverter or power conversion system, or PCS
- Existing controller or communications gateway
- Site meter and current transformer, or CT, clamps
- Export-limitation equipment
The EMS supplier can then check the technical documents for the exact inverter model and firmware version. You do not need to find or interpret register maps, API guides, or integration manuals yourself.
The EMS needs enough live data to control the battery correctly, including:
- The amount of charge in the battery
- The battery’s current charging or discharging power
- The charging and discharging power available
- The inverter’s operating status and alarms
- The amount of electricity the client imports and exports
- The battery’s operating limits
The EMS must also send instructions back to the inverter. For example, it may tell the inverter how many kilowatts to charge or discharge at a particular time.
A Modbus connection or manufacturer API does not always let a third-party EMS control the battery. Some inverter manufacturers let third-party software read monitoring data but do not let it send charging and discharging instructions.
The EMS supplier also needs to confirm which controller the inverter follows when several controllers send instructions. This could be:
- The manufacturer’s EMS
- The export limiter
- The existing battery schedule
- The third-party EMS
If the manufacturer’s EMS, export limiter, or existing battery schedule retains priority, the inverter may ignore instructions from the third-party EMS. The inverter only follows those instructions when the correct external-control mode is active.
What on-site tests prove the EMS can control the battery?
On site, the EMS supplier needs to prove that the EMS can read the correct data, send charging and discharging instructions, and respond safely to limits or a loss of communications.
Before commissioning, ask the EMS supplier to confirm:
- Whether the retrofit requires a gateway, protocol converter, or firmware update
- Whether external control could affect the battery or inverter warranty
- Whether the existing import and export controls can block any instruction that would breach the client’s limits
- How the battery responds if the EMS controller loses contact with the inverter or the internet connection fails
The EMS supplier should first check the readings without sending any charging or discharging instructions. Once the supplier confirms that the EMS reads the data correctly, they can test:
- Small charging and discharging instructions
- Battery operating limits
- Alarms
- Which controller takes priority
- Loss of communications
The EMS software can only control the battery correctly when it receives accurate data for the whole site. Check that:
- The meter and CT clamps measure imports and exports at the correct point
- The meter or controller uses the correct CT ratio
- The CT clamps face the correct direction
- The meter sends new readings quickly enough for the EMS
Inverter compatibility alone does not prove that the EMS can control the client’s battery. The EMS must also work with the site meter, communications gateway, and any export-limitation equipment already at the premises.
Only treat the system as compatible after the on-site tests show that the EMS can read the required data, send the required instructions, and pass the fallback test on the client’s equipment.
The client may still be able to use the EMS after the project team adds a new meter or gateway or updates the firmware. However, if the inverter connection only lets the EMS read monitoring data, the EMS cannot control charging or discharging.
Related questions
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