IMPORTANT NOTE: Redflow does not provide Victron system installation training - installers unfamiliar with Victron products should first obtain Victron training from Victron Energy directly.
The Venus/CCGX product is the Energy Management System (EMS) for the Victron Energy product architecture. Venus is the software, and it runs in multiple choices of Victron hardware (CCGX, Venus-GX, Octo-GX etc).
Venus gathers data from all core energy system components (grid meter, solar metering, load metering, battery management system) and commands appropriate charge/discharge via the Victron Energy Quattro inverter/chargers as required.
The Victron Energy solar-self-consumption application built into the Victron components is called “ESS”.
To operate solar-self-consumption applications, an "ESS Assistant" must be loaded into all of the Multi or Quattro devices in the installation using VE.Configure. Overall ESS operation is ten configured using the ESS menu on the Venus system.
The control architecture for a large Redflow ZBM2 based Victron energy system is exactly the same as for a smaller Victron Energy system built using any other form of CANBus-connected (i.e. ‘smart BMS’) based battery and running ESS (The standard Victron solar-self-consumption control system built into the Victron Venus/CCGX EMS product).
The BMS interface and ESS system is connected and configured as for any other Victron system using any ’smart’ (CANBus interfaced) battery, in accordance with the Victron installation manual here:
[ See especially the specific information regarding Redflow installations on that page, in section 4.3, "Venus-device - ESS Settings”, for the configuration specifics with Redflow batteries ]
The Redflow BMS hardware can attach directly to up to 12 batteries per BMS without additional hardware. The BMS can connect to up to 16 batteries if a MODBUS RS485 repeater or hub is used to boost MODBUS signal strength.
Beyond 16 batteries in total on a given DC bus, systems are best built using a simple master/slave BMS arrangement, with one ’Slave’ BMS per (up up) 16 ZBM2 units, and one additional ‘Master” BMS installed.
The Master reads and aggregates data from all of the slaves (via TCP/IP over Ethernet) and presents the overall system status data via CANBus to the Victron Venus/CCGX system.
Redflow will be pleased to assist with the initial configuration of the Master/Slave arrangement for large systems as required.
For reference in terms of what needs to be done:
- The initial connection of the CANBus physical cable path from the Master Redflow BMS to the CCGX is documented here.
- The initial configuration of each slave BMS is documented here
- Enabling Master BMS mode must currently be done by Redflow technical staff (and can be done remotely) - just ask. Configuring Master BMS mode directly will be supported in the BMS installer interface in a future BMS software release.
- The initial interfacing to the Victron CCGX, while covered on the Victron installation guide noted above, is also covered (in terms of Redflow differences to any other standard Victron system) here
The list of components needed is:
- One Victron Venus EMS device (CCGX or Venus-GX or Octo-GX etc - they are all functionally identical, and differ only in I/O capability - all will work fine for any Redflow battery system)
- One Redflow ‘slave’ BMS per (up to) 16 ZBM2’s plus one more BMS as the system Master
- One RS485 Hub or repeater per Slave BMS if more than 12 batteries are connected to each slave (required only if 13, 14, 15 or 16 ZBM2s are connected to a single BMS).
- One Victron Energy Filax 2 AC Automatic Transfer Switch (ATS) to ensure power continuity to the components above, connected via a pair of AC to DC power supply units (for redundancy) - see this guide for more information.
An example of this equipment in a large system is pictured below.
This particular system interfaces to 45 Redflow ZBM2 batteries on a single 48V DC bus bar structure, split into 3 physical in a shipping-container form-factor. Each bank contains 15 batteries.
Left-to-right you can see:
- Victron Filax 2 AC transfer switch (sourcing energy automatically from the the grid and from the Victron Energy system AC output)
- Victron Energy CCGX running the Victron Venus platform
- Dual-redundant AC-to-DC power supplies (24V DC output - note this can be anything from 9-60VDC as required but 24V is readily available and widely accepted by pretty much all DC devices in this realm)
- Cabinet containing 4 x BMS units and 3 x RS485 signal repeater modules plus an ethernet switch (not visible) to interconnect the CCGX and the four BMS modules (note in this particular installation the three slaves have different front panel labels but this is not significant)
Monitoring the operation of the overall Energy Management System (EMS)
In terms of interface to any site ‘Building Management System’, this is most simply achieved using MODBUS-TCP data retrieval from the Victron Venus/CCGX platform.
The MODBUS-TCP access mechanism for this is documented by Victron here:
And the MODBUS-TCP register map from the CCGX platform is available by clicking here and then clicking on "MODBUS-TCP Register List”:
While we are happy to help, please note that the MODBUS-TCP interface noted above is not provided by, or supported by, Redflow; Redflow simply supplies the batteries.
The actual EMS is the standard Victron product, operating exactly as if it was using any other type of ’Smart’ (BMS-interfaced) battery.
More specific information on the battery array performance can be obtained from the Redflow Master BMS via MODBUS-TCP or JSON queries.
If you wish to directly query the BMS in this manner, there is a full list of MODBUS-TCP and JSON query URLs provided on every Redflow BMS - just log in to your BMS and go to this page for the full access information:
Tools->Field Access Information
However please note that the core battery status information obtained in this way is identical to that rendered by the Venus/CCGX unit.
The CCGX is the only source of holistic data on the overall energy system performance - including performance and usage data beyond the batteries - and hence it is the preferable primary information source to be used by any higher level Building Management System where Victron Energy components are used to build the EMS.
MODBUS Battery Limitations : Further Detail
The following are the reasons why more than 12 batteries per BMS requires special installation considerations.
The primary limitation is electrical. The noise suppression hardware on each ZBM2 draws enough power that the maximum un-assisted MODBUS signal chain length is 12 ZBM2 batteries.
For systems that require more than 12 batteries per slave an RS485 repeater or hub is required. This is simply to boost signal strength on the MODBUS daisy-chain.
The brand or type of the RS485 repeater is non-critical, and it is sufficient to obtain and run a simple repeater (one 'in' and one 'out' port) somewhere in the middle of the end-to-end chain of MODBUS cabling to the battery string.
In large systems, however, it can be inconvenient to locate and power a simple repeater located 'in amongst the batteries'. Rather, it can be far more convenient to use a multiport RS485 hub located beside the BMS cabinet and to run multiple shorter strings from that location out to the batteries in a 'star' pattern instead.
This approach is used in the example system pictured above, and for reference the RS485 hub unit in this installation is a "UT-5204" - as per the photographs below.
These units were simply purchased (new) via eBay and run on the same 24V DC power as the other control system components. They are passive devices, requiring no configuration, that work independently of RS485 signal protocol or baud rate.
The next limitation (16 batteries per BMS) even with an RS485 signal strength boost, is a limitation derived from the rate at which the BMS can retrieve data from all connected batteries while still being sufficiently responsive to the upstream energy management system. It is not an absolute limit, but response speed to changes in battery status would become very slow above this size.
The BMS collects a lot of data from each battery each time that it polls for information, and the current MODBUS speed to the batteries is relatively low (19,200 baud).
Redflow may increase the baud rate of the ZBM2 electronic control device (MMS) in the future to allow more batteries to be installed per BMS. However, due other MODBUS processing speed limitations that still exist even at a higher underlying MODBUS baud rate (and are intrinsic to MODBUS) this may not yield a significant practical increase in number of connectable batteries onto a singe BMS.
One master can easily handle many slaves, because the communication concerned is via ethernet between the BMS units. A BMS cluster with up to 60 parallel ZBM2's can be built today with ease in this way (e.g. 5 slaves x 12 batteries or 4 slaves x 15 batteries).
A total of 60 connected ZBM2 batteries on a single DC bus is approaching the pragmatic/practical limit for a single overall system. At this size, the required DC bus to handle peak DC current, the size of fusing required, and and the practical maximum size of the associated Victon Energy Quattro cluster are all approaching their reasonable limits.