8. DVCC - Distributed Voltage and Current Control
8.1. Introduction and features
Enabling DVCC changes a GX device from a passive monitor into an active controller. The available features and effects of enabling DVCC depend on the type of battery used. The effect also depends on the installed Victron components and their configuration. Two examples:
Managed CAN-bus batteries: In systems with a managed CAN-bus BMS battery connected, the GX device receives a Charge Voltage Limit (CVL), Charge Current Limit (CCL) and Discharge Current Limit (DCL) from that battery and relays that to the connected inverter/chargers and solar chargers. These then disable their internal charging algorithms and simply do what they're told by the battery.
Lead-acid batteries: For systems with lead-acid batteries, DVCC offers features such as a configurable system-wide charge current limit, where the GX device actively limits the inverter/charger if the solar chargers are already charging at full power, as well as Shared Temperature Sense (STS) and Shared Current Sense (SCS).
This table shows the recommend settings for different battery types:
Lead-acid | VE.Bus BMS V1 Lithium | VE.Bus BMS V21) Lithium | Supported 3rd party managed batteries2) | |
|---|---|---|---|---|
1) DVCC must be enabled for the GX device to control the solar chargers, Inverter RS or Multi RS in a system with a VE.Bus BMS V2. 2) Use the Battery Compatibility manual to see which parameters need to be set and which are set automatically. 3) In an ESS system the VE.Bus device is already synced with the solar chargers, so we recommend leaving SVS and SCS off. 4) For all other systems: If a BMV or SmartShunt is installed, we recommend enabling SVS and SCS. In all other cases, leave SVS and SCS disabled. 5) Solar Chargers, Inverter/Chargers, Multi RS and Inverter RS do not require wiring. All other loads and chargers must be wired and controlled via ATC/ATD. | ||||
Auto-config | No | No | No | 2) |
System charge current | Yes | Yes | Yes | 2) |
Should you enable SVS? | Yes | 3), 4) | 3), 4) | 2) |
Should you enable STS? | Yes | No | No | 2) |
Should you enable SCS | Yes | 3), 4) | 3), 4) | 2) |
Charge control method | N/A | N/A | N/A | 2) |
Wire ATC & ATD | N/A | Yes | 5) | 2) |
To enable or disable DVCC, go to Settings → DVCC on the GX device:
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8.2. DVCC Requirements
Battery compatilibity
For CAN-bus connected batteries, check the relevant page on the Battery Compatibility manual to see if enabling DVCC has been tested with your battery type and is supported. If DVCC is not mentioned in notes relating to your battery, do not enable DVCC.
For Gel, AGM, OPzS and other lead-acid batteries, DVCC can be used without any problem. The same is true for Victron Energy Lithium Battery Smart with the VE.Bus BMS, the Lynx Ion + Shunt BMS or the Lynx Ion BMS. DVCC is forced-enabled for the Lynx Smart BMS.
Firmware versions
Do not use DVCC in cases where these requirements are not met. In all cases we recommend to install the latest available firmware during commissioning. Once running well, there is no need to proactively update firmware without reason. In case of difficulty, the first action is to update firmware.
Required minimum firmware versions:
Multi/Quattro: 422
MultiGrid: 424
Multi RS, Inverter RS and MPPT RS: v1.08
GX device: v2.12
VE.Direct MPPTs: v1.46
VE.Can MPPTs with VE.Direct: v1.04
Older style VE.Can MPPT Solar Chargers (with the screen) cannot be used: they do not support the new control mechanisms.
Lynx Ion + Shunt: v2.04
Lynx Ion BMS: v1.09
Lynx Smart BMS v1.02
From Venus firmware v2.40, there will be a warning message 'Error #48 - DVCC with incompatible firmware' when one of the devices has an incompatible firmware while using DVCC.
In case of an ESS System, the ESS Assistant needs to be version 164 or later (released in November 2017).
8.3. DVCC effects on the charge algorithm
In standalone mode, our inverter/chargers and MPPT solar chargers use their own internal charging algorithm. This means that they determine how long to remain in Absorption, when to switch to Float, when to switch back to Bulk, or Storage. And in those various phases they use the configured parameters in VictronConnect and VEConfigure.
In ESS systems and systems with managed battery (see the Battery Compatibility manual), the internal charge algorithm is deactivated and the charger then works with an externally controlled charge voltage setpoint. This table explains the different possibilities:
Selection guide | Resulting charge algorithm | |||
|---|---|---|---|---|
1) The ESS Assistant is only installed in a specific type of power system that integrates a grid connection with a Victron inverter/charger, GX device and battery system, not to be confused with an off-grid system such as is used in boats or RVs. | ||||
System type | Battery type | DVCC | Inverter/charger | Solar charger |
ESS Assistant1) | Intelligent battery | On | Battery | Battery |
Off | Don't do this; better enable DVCC | |||
Normal battery | On | Internal | Inverter/charger | |
Off | Internal | Inverter/charger | ||
Standard | Intelligent battery | On | Battery | Battery |
Off | Don't do this; better enable DVCC | |||
Normal battery | On | Internal | Internal | |
Off | Internal | Internal | ||
Internal
The internal charge algorithm (bulk → absorption → float → re-bulk), and the configured charge voltages are active.
Inverter/charger indicated charge state: bulk, absorption, float, and-so-forth.
MPPT solar charger indicated charge state: bulk, absorption, float and-so-forth (firmware version v1.42 onwards. Earlier versions have a bug that make the MPPT solar charger say “Ext. Control” when it is only being current limited; its internal charge algorithm is still active.).
Inverter/charger (applies to MPPTs only)
The MPPTs internal charge algorithm is disabled; instead it's being controlled by a charge voltage setpoint coming from the inverter/charger.
MPPT solar charger indicated charge state: Ext. control.
Battery
The internal charge algorithm is disabled and instead, the device is being controlled by the battery.
Inverter/charger indicated charge state: Ext. control.
MPPT solar charger indicated charge state: Ext. control (the LEDs continue to show bulk and absorption, never float).
8.4. DVCC features for all systems
These features apply to all types of systems when DVCC is enabled; with or without ESS Assistant, with lead-acid or other normal batteries as well as when an intelligent CAN-bus BMS connected battery is installed:
8.4.1. Limit charge current
Limit charge current is a user-configurable maximum charge current setting. It works across the whole system. MPPT solar chargers are automatically prioritised over the mains/generator.
This setting is available in the Settings → System setup menu on the GX device:
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Particulars:
1) If a CAN-bus BMS is connected and the BMS requests a maximum charge current that is different from the user-configurable setting, the lower of the two will be used.
2) This mechanism only works for Victron inverter/chargers including Inverter RS, Multi RS and Solar chargers incl. MPPT RS. Other chargers, such as Skylla-i’s are not controlled and also their charge current is not taken into account. The same applies for devices that are not connected to the GX device, such as an alternator. Worded differently: the total charge current of the inverter/chargers and all MPPT solar chargers will be controlled, nothing else. Any other sources will be extra charge current, unaccounted for. Even when installing a BMV or other battery monitor.
3) DC Loads may not be accounted for, unless a SmartShunt or BMV-712 is installed and correctly configured as a DC meter. For example, without the DC load monitor a configured maximum charge current of 50A and DC Loads drawing 20A, the battery will be charged with 30A, not with the full allowed 50A. With the SmartShunt configured as a DC meter, maximum charge current configured at 50A and DC system shunt reports a draw of 25A, then the chargers are set to charge with 50 + 25 = 75A.
If you have one or more shunts configured for "DC system" (when more than one, they are added together), then the DVCC charge current limit compensates for both loads and chargers. It will add extra charge current if there is a load, and subtract it if there is another charger in the DC system. DC "loads" and "sources" are not compensated for in either direction.
4) Current drawn from the system by the inverter/charger is compensated for. For example, if 10A is drawn to power AC loads and the limit is set to 50A, the system will allow the MPPT solar chargers to charge with a maximum of 60A.
5) In all situations, the maximum charge limit configured in a device itself, i. e. the Charge current limit set with VictronConnect or VEConfigure for MPPT solar chargers or inverter/chargers will still be in effect. An example to illustrate this: in case there is only an inverter/charger in the system and in VEConfigure or VictronConnect the charge current is configured to 50A. And on the GX device, a limit of 100A is configured, then the working limit will be 50A.
6) DVCC charge current limits are not applied to DC MPPTs when ESS is enabled with Allow DC MPPT to export. This is to get maximum output from the solar panels for export.
8.4.2. Limit managed battery charge voltage
Some batteries (like BYD and Pylontech) that come from the factory will take some time to settle in, and you may need to run them at a lower voltage for the first two weeks or so to help them balance.
This is what Limit managed battery charge voltage is designed for. Enabling this makes it possible to lower the maximum charge voltage until cells have balanced.
Do not use it for any other purpose as it may have unwanted side effects, for example, balancing can fail or not start at all if the charge voltage is set too low, causing the battery cells to become severely imbalanced over time. It is also not possible to set the value above the charge voltage limit (CVL) sent by the battery.
8.4.3. Shared Voltage Sense (SVS)
Works with VE.Bus devices, VE.Direct and VE.Can MPPT solar chargers as well as Inverter RS and Multi RS.
The system automatically selects the best available voltage measurement. It will use the voltage from the BMS or a BMV battery monitor, if possible, otherwise it will use the battery voltage reported by the VE.Bus system.
The voltage displayed on the GUI reflects the same voltage measurement.
Shared Voltage Sense (SVS) is by default enabled when DVCC is enabled. It can be disabled with a switch in Settings → DVCC.
SVS (and DVCC) is force enabled for the Lynx Smart BMS and cannot be changed.
Note that SVS is force-disabled for some batteries. Please see the compatibility page for your battery.
8.4.4. Shared Temperature Sense (STS)
Select the temperature sensor to use; and the GX device will send the measured battery temperature to the inverter/charger system as well as all connected solar chargers.
Selectable sources for the battery temperature are:
BMV-702 battery monitor
BMV-712 battery monitor
SmartShunt
Lynx Shunt VE.Can battery monitors
Temperature inputs on a Cerbo GX (and same for other GX devices that have a temperature input)
Multi/Quattro inverter/charger
Solar chargers (if fitted with a temperature sensor)
8.4.5. Shared Current Sense (SCS)
This feature forwards the battery current, as measured by a battery monitor connected to the GX device, to all connected solar chargers.
The solar chargers can be configured to use the battery current for its tail current mechanism that ends absorption when the current is below the configured threshold. For more information about that, refer to solar charger documentation.
This feature only applies to systems that are not ESS and/or don’t have a managed battery, since in both of those cases the MPPT is already externally controlled.
Requires MPPT solar charger firmware v1.47 or newer.
8.5. DVCC features when using CAN-bus BMS battery
This chapter applies to all systems where an intelligent battery BMS is installed and connected via CAN-bus. Note that this does not include the Victron VE.Bus BMS.
Such intelligent BMS sends the following parameters to the GX device:
Charge voltage limit (CVL): the maximum charge voltage that the battery currently accepts.
Charge current limit (CCL): the maximum charge current requested by the battery.
Discharge current limit (DCL): the maximum discharge current as requested by the battery.
For all three parameters, some types of batteries transmit dynamic values. For example they determine the maximum charge voltage based on cell voltages, state of charge, or for example temperature. Other makes and brands use a fixed value.
Here is the page in the menus showing the parameters:
For such batteries, there is no need to wire allow to charge (ATC) and allow to discharge (ATD) connections to the AUX inputs of a Multi or Quattro.
When inverting, i. e. in island mode, Multis and Quattros will shut down when the max discharge current is zero. They will automatically start again as soon as either AC mains returns or when the BMS increases the max discharge current again.
See previous section Limit charge current, the user-configurable maximum charge current setting, for details about how the Maximum charge current is used, how it prioritises solar and more.
All above means that setting up charge voltages or charge profiles in VEConfigure or VictronConnect is not necessary and will also have no effect. The Multis, Quattros, Multi and Inverter RS and MPPT Solar Chargers will charge with the voltage as received via CAN-bus from the battery. This also applies to systems with a Lynx Smart BMS connected to a GX device.
8.6. DVCC for systems with the ESS Assistant
The ESS Keep batteries charged mode will only work properly with DVCC enabled.
A fixed solar offset of 0.4V (value for 48V system, divide by 4 for 12V) is applied when ESS-mode is set to Optimised in combination with the Feed-in excess solar charger power-setting enabled, or when ESS-mode is set to Keep batteries charged.
For system with ESS mode Optimised and Optimised (with BatteryLife): The system will automatically recharge the battery (from the grid) when the SoC drops 5% or more below the value of ‘Minimum SoC’ in the ESS menu. Recharge stops when it reaches the Minimum SoC.
ESS status display in the graphic overview of the GX device: In addition to the charge status (External Control or Bulk/Absorption/Float), the following status can be displayed:
#1: Low SoC: discharge disabled
#2: BatteryLife is active
#3: Charging disabled by BMS
#4: Discharging disabled by BMS
#5: Slow charge in progress (part of BatteryLife, see above)
#6: User configured a charge limit of zero.
#7: User configured a discharge limit of zero.
Note: When DC-coupled PV feed-in excess is enabled with ESS, the DVCC system will not apply the DVCC charge current limit from PV to battery. This behaviour is necessary to allow the export. Charge voltage limits will still apply.
Charge current limits set at the individual solar charger device settings level will also still apply.
When the BMS is disconnected in an ESS system, solar chargers will stop and show error #67 – No BMS (see the MPPT Solar Charger Error Codes for additional info).