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--- ess:design-installation-manual [2018-05-15 12:33] – [9. FAQ] mvader
+++ ess:design-installation-manual [2020-08-09 21:53] – [6. Controlling depth of discharge] jono
@@ Line 1: / Line 1: @@
 ====== ESS Design & installation manual ======
+{{:ess:ess_diagram.jpg?direct&400|}}
 ===== 1. ESS Introduction & features =====
@@ Line 5: / Line 7: @@
 === What is ESS? ===
-An ESS (Energy Storage System) is a grid-tie installation, incorporating solar and battery-storage, which //behaves// as though it were an off-grid installation ...thereby enjoying the best of both worlds. When it is able to produce more power than it can use and store, it sells the surplus to the grid; and when it has insufficient stored power, it buys electricity from the grid. This is available from using a combination of standard multipurpose Victron products, setup with an ESS configuration. In the system, there must at least be one inverter/charger and also a Venus-device:
+An Energy Storage System (ESS) is a specific type of power system that integrates a power grid connection with a Victron Inverter/Charger, [[venus-os:start|GX device]] and battery system. It stores solar energy into your battery during the day, for use later on when the sun stops shining.
+It allows for time shifting power, charging from solar, providing grid support, and exporting power back to the grid.
+When an ESS system is able to produce more power than it can use and store, it can sell the surplus to the grid; and when it has insufficient energy or power, it automatically buys it from from the grid.
+In the ESS system, there must at least be one inverter/charger and also a [[venus-os:start|GX device]] such as:
-  * [[https://www.victronenergy.com/panel-systems-remote-monitoring/color-control|Color Control GX]]
+  * [[https://www.victronenergy.com/panel-systems-remote-monitoring/cerbo-gx|Cerbo GX]]
   * [[https://www.victronenergy.com/panel-systems-remote-monitoring/venus-gx|Venus GX]]
@@ Line 30: / Line 38: @@
 Configuring ESS in a system which uses a diesel generator as backup - for extended mains failures - can be achieved. Grid code and Loss of Mains configuration will need special attention, see [[ve.bus:grid-codes-and-loss-of-mains-detection|here]].
-And on the Venus-device, select 'Generator' as the AC Input type in the Settings -> System setup menu. The system will then enable generator charging; ensure that the generator is properly loaded, and will be automatically switched-off as soon as parameters are met.
+And on the [[venus-os:start|GX device]], select 'Generator' as the AC Input type in the Settings -> System setup menu. The system will then enable generator charging; ensure that the generator is properly loaded, and will be automatically switched-off as soon as parameters are met.
 === When not to use ESS ===
@@ Line 46: / Line 54: @@
 Where there is no grid-meter; all loads are connected to AC-out. And where there is a PV Inverter present, that is also connected to AC out.
+{{:ess:ess_no_meter.jpg?direct&400|}}
 === Optional feed-in of MPPT Solar charger power ===
@@ Line 64: / Line 74: @@
   * [[https://www.youtube.com/watch?v=QxoHfBBGnt4&index=2&list=PLnKCJA0l3E6bKtlcvIgCy-bB2wvryr5i8|ESS Webinar 2016-12-19 Youtube (ES)]]
   * {{ :ess:2016_-_ess_training2.pptx |ESS Webinar 2016-12-19 PPT}}
+=== Energy Storage System introduction, examples and diagrams ===
+A seperate document that provides further introductory information, overviews, and system examples is available to [[https://www.victronenergy.com/upload/documents/Brochure-Energy-Storage-EN_web.pdf|download here]].
 === Advanced control options ===
@@ Line 89: / Line 104: @@
 The Energy Storage system, uses a [[https://www.victronenergy.com/inverters-chargers|Multi or Quattro bidirectional inverter/charger]] as its main component.
-=== Venus-device ===
+Note that ESS can only be installed on Multis and Quattros which feature the 2nd generation microprocessor (26 or 27). All new systems shipped have 2nd generation chips.
+=== GX device ===
 The system is managed by the [[https://www.victronenergy.com/panel-systems-remote-monitoring/color-control|Color Control GX (CCGX)]], which also provides extensive monitoring, both locally and remotely via our [[https://vrm.victronenergy.com/|VRM Portal]] and the [[https://www.victronenergy.com/support-and-downloads/software#victron-vrm-app|VRM App]].
@@ Line 133: / Line 150: @@
 For a full or partial grid-parallel installation an Energy Meter can be installed in the main distribution panel between the grid and the installation.
-https://www.victronenergy.com/live/energy-meter
+A grid meter is not required where there are no AC renewable-energy source(s) and also no AC load(s) present on the the //input// side of the Multi/Quattro system (i.e. where all such sources and loads are on the //output// side of the Multi/Quattro system).
-A grid meter is only //required// when there is an additional energy source (e.g. PV) connected between the grid and the //input// side of the Multi/Quattro systems. If all renewable-energy sources are connected 'downstream' (on the output side) of the inverter/chargers a grid meter will not be required, but can be added.
+If there is any AC renewable energy source //or// any AC load between the grid connection point and the input side of the Multi/Quattro system, incorrect results will be calculated and recorded by the GX unless a grid meter is installed and enabled.
+In particular, without a grid meter:
+  * When renewable energy is being provided on the input side, the grid value will be wrong (too low/negative); and
+  * The AC Load value shown will be too low (and will show zero where there is a surplus of renewable energy).
+Both issues are resolved by installing a grid meter.
+[[https://www.victronenergy.com/live/energy-meters:start|Click here for more information about the configuration of grid meters.]]
 === PV (optional) ===
@@ Line 259: / Line 285: @@
 Update all components to the latest firmware version:
-  - Venus-OS v2.00 or newer. Instructions to upgrade to v2.00 [[ccgx:firmware_upgrade_to_v2|here]].
+  - Venus-OS v2.15 or newer. Instructions to upgrade to v2.00 can be found [[ccgx:firmware_upgrade_to_v2|here]].
-  - Multi, MultiGrid, MultiPlus or Quattro to 408 or newer. Instructions [[updating_firmware:updating_ve.bus_products|here]].
+  - Multi, MultiGrid, MultiPlus or Quattro to 422 or newer. Instructions [[updating_firmware:updating_ve.bus_products|here]].
   - Solar Chargers, either VE.Can or VE.Direct must run their latest firmware version.
@@ Line 293: / Line 319: @@
   * When using a VE.Bus BMS and a Multi Compact, check the DIP switches: DIP switch 1 must be on, and DIP switch 2 must be off.
-==== 4.3 Venus-device - ESS Settings ====
+==== 4.3 GX device - ESS Settings ====
 Navigate to Settings -> ESS, to see this menu:
@@ Line 321: / Line 347: @@
   * Victron 12.8V Lithium batteries, and other lithium batteries that have passive cell balancing
-Because it makes no sense to leave a battery discharged, without reserve power in case of mains failure, we recommend leaving BatteryLife enabled on the following battery technologies, too:
+Because it makes no sense to leave a battery discharged, without reserve power in case of mains failure, we recommend leaving BatteryLife enabled for systems using Lithium with active cell balancing, however it //can// be disabled in this case.
-  * Lithium with active cell balancing
+Redflow specifies that BatteryLife should be disabled in [[battery_compatibility:redflow_zcell|Redflow ZCell]] installations, because the ZCell battery can rest at zero SoC without damage for an unlimited period, and also because the BatteryLife function conflicts with the ZCell battery maintenance cycle.
-  * [[battery_compatibility:redflow_zcell|Redflow ZCell]]
-  * [[battery_compatibility:aquion_ahi|]]
-However, BatteryLife //can// be disabled in these cases.
+=== 4.3.2 Grid meter installed ===
-=== 4.3.2 Control without grid meter ===
+Leave Off when no Victron grid meter is installed, and set to 'On' when such meter is installed.
-Set to 'On' to enable ESS on a system without grid meter. All loads and (optional) grid-tie inverters must be installed on the AC out.
+All loads and (optional) grid-tie inverters must be installed on the AC out in a system without a Victron grid meter. See earlier in the manual for more information.
 === 4.3.3 Inverter AC output in use ===
@@ Line 340: / Line 364: @@
 Set to 'On' to make the Solar Charger always operates at its maximum power point. The first priority is powering the loads, and the second priority is to charge the battery. If more power is available when those two priorities are met, then that power will be fed to the utility grid.
+Please note that when enabling this option, the DVCC charge current limit configured under Settings -> Limit charge current won't be active. The Solar charger will operate at full power for maximum feed-in into the grid. It's advisable to configure a safe limit on the solar chargers when used with a small battery bank.
 === 4.3.5 Phase compensation ===
@@ Line 364: / Line 390: @@
   * //Slow charge//: ESS will slowly charge the battery when the SOC has been below the actual SOC limit for more than 24 hours. It will keep slow charging until the lower limit has been reached at which point the system once again switches to //Discharge disabled//.
   * //Sustain//: the Multi/Quattro has gone into sustain mode after the battery voltage has reached the dynamic cut-off voltage during discharge.
+  * //Recharge//: ESS will recharge the battery to the minimum SOC limit if it drops more than 5% below the minimum configured SOC. Once the minimum SOC is reached the system once again switches to //Discharge disabled//.
 === 4.3.9 Limit charge power ===
-This setting limits the amount of AC power used by the Multi for battery charging. The limit also applies to AC power received by the Multi from a grid-tie PV Inverter.
+This setting limits the amount of AC power used by the Multi for battery charging. The limit also applies to AC power received by the Multi from any grid-tie PV Inverters connected to AC-in.
-In other words, this setting limits the flow of power from AC to DC.
+In other words, this setting limits the flow of power from AC to DC on utilities connected to AC-in.
   * This setting does not reduce the charge power coming from //MPPT Solar Chargers//.
@@ Line 395: / Line 422: @@
   * In the same menu, set Sunspec Model Type to int + SF
   * In Settings->DNO Editor, make sure dynamic power reduction is set to No limit (this is the default).
+  * In Settings->DNO Editor, make sure that in the 'Controlling Priorities' section that 'Controlling via Modbus' is set to be priority 1.
+{{:ess:settings-dno-priority.png?400|}}
 Use the __Fronius Zero feed-in active__ menu item to double check that all above criteria are met. It will show **No** if the firmware requirement; the Data export; or the Sunspec Model type settings are incorrect.
+Do not use a Fronius Smart Meter for limiting export when part of a Victron ESS System. More details about when a Fronius Smart Meter can, and can not be used is explained [[ac_coupling:fronius|here]].
 === 4.3.12 Grid setpoint ===
 This sets the point at which power is taken from the grid when the installation is in self-consumption mode. Setting this value slightly above 0W prevents the system from feeding back power to the grid when there is a bit of over-shoot in the regulation. The default value is therefore 50W - but should be set to a higher value on large systems.
-==== 4.4 Venus-device - Other settings ====
-=== 4.4.1 Settings -> System setup -> AC Input types ===
+==== 4.4 GX device - Scheduled Charging ====
+=== 4.4.1 Introduction ===
+The Scheduled Charging setting is located in the ESS menu of the [[venus-os:start|GX device]]. It allows you to set up to five scheduled periods, during which the system will take power from the grid to charge the battery. This is typically used to charge the battery during off-peak tariff time windows (TOU). For each schedule, configure a start-time, duration, and optionally set the percentage up to which you want the battery to be charged.
+If the target state of charge is reached, and it is still within the period of time set, the battery will stop charging but will not discharge (unless there is grid outage). This optimises battery cycling and still allows room in the battery for PV charging.
+=== 4.4.2 Configuration ===
+Scheduled charging is available as part of ESS. It is accessible on the [[venus-os:start|GX device]] menus under Settings -> ESS. It is only available when the ESS mode is set to Optimised. Scheduled charging naturally makes no sense when the mode is set to Keep Batteries Charged.
+You can see at a glance what is configured, with a summary of the start day, time and duration shown for each.
+{{:scheduled_charging:main.png?nolink |}}
+{{::scheduled_charging:schedule.png?nolink|}}
+For each schedule you can select a specific day of the week, every day of the week, or you may opt to charge on all weekdays or only on weekends.
+{{:scheduled_charging:selectday.png?nolink|}}
+The Multi will start charging from the grid at the specified start time, and stop after the set duration or when the set SOC limit is reached. The period designated by the day, start time and duration will subsequently be referred to as a scheduled charge window.
+During charging, the ESS state will indicate that Scheduled Charging is in progress.
+{{::scheduled_charging:overview.png?nolink |}}{{::scheduled_charging:tiles.png?nolink|}}
+=== 4.4.3 Stop charge on SOC ===
+When a SOC limit is set for a scheduled charge window, charging will stop when the batteries reach the requested SOC. The batteries will however not discharge until the scheduled charge window ends. The goal is to be at or near the requested SOC at the end of the scheduled charge window.
+=== 4.4.4 Frequently asked questions ===
+== Why does the Multi not discharge the battery after charging ends? ==
+Discharge is disabled until the end of the scheduled charge window. The goal is to exit the window at the requested SOC.
+== How can I prevent discharge to reserve battery capacity for later in the day? ==
+Set a charge window for the required period with a low SOC Limit. Discharge is disabled in a scheduled charge window.
+== What happens if I set overlapping schedules? ==
+The first matching schedule takes priority. If the two schedules have different SOC limits, the limit of the second matching scheduled charge window takes effect after the first scheduled charge window ends.
+==== 4.5 GX device - Other settings ====
+=== 4.5.1 Settings -> System setup -> AC Input types ===
 Set the AC Input type to //Generator// when connected to a generator. The system will then enable generator-charging and correctly load the generator when running.
@@ Line 409: / Line 487: @@
 Note that we recommend wiring the Generator to AC-in 1, and the Grid to AC-in 2. The reason is that the Quattro will then prioritize the Generator over the Grid. That arrangement offers maximum flexibility (allowing forced generator intervention even when the grid is available) and maximises control.
-=== 4.4.2 Settings -> Generator start/stop ===
+=== 4.5.2 Settings -> Generator start/stop ===
 More information on controlling remote generator start/stop is available [[ccgx:generator_start_stop|here]].
-==== 4.5 MPPT Solar Charger ====
+==== 4.6 MPPT Solar Charger ====
 In ESS, the MPPT Solar Chargers will follow the charge curve as set in VEConfigure. The charge parameters configured in the MPPT Solar Chargers themselves are ignored in an ESS setup.
@@ Line 458: / Line 537: @@
 Start the generator and check that the system begins to charge the batteries.
 ===== 6. Controlling depth of discharge =====
-//(Note: All absolute voltages mentioned in the example below refer to a 12V system. Voltages should be multiplied by x2 or x4 for a 24V or 48V system, respectively.)//
+//(Note: All absolute voltages mentioned in the example below refer to a 12V system. Voltages should be multiplied by x2 for a 24V system or x4 for a 48V system.)//
 ==== 6.1 Overview ===
@@ Line 549: / Line 628: @@
 (This 0.1 V is the threshold for 12 V systems; for 24 V the threshold is 0.2 V above; and for 48 V it is 0.4V above.)
+==== 6.5 ESS Battery Status Reason Code Numbers ====
+In addition to the charger states (Bulk/Absorption/Float), there are additional Discharging and Sustain codes that provide at-a-glance information on the Pages Overview of GX display.
+{{:ess:victron_-_ess_codes.jpg?direct}}
+The key for these codes is:
+  * #1: SOC is low
+  * #2: BatteryLife is active
+  * #3: BMS disabled charging
+  * #4: BMS disabled discharge
+  * #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.
 ===== 7. Phase compensation - further information =====
@@ Line 566: / Line 663: @@
 __Single phase ESS in a system with a three-phase connection to the utility grid__
+Single phase ESS is a single inverter/charger.
   * Phase Compensation enabled: ESS regulates total power L1 + L2 + L3 to 0.
@@ Line 571: / Line 670: @@
 __Three phase ESS in a system with a three-phase connection to the utility grid__
+Three phase ESS is, at least, three inverter/chargers: one on each phase.
   * Phase Compensation enabled: ESS prevents circumstances where the battery might be charging on one phase whilst discharging on another.
@@ Line 589: / Line 690: @@
 (Make sure you install the ESS on L1. If it's installed on another phase the visualisation will be wrong.)
-==== 7.2 Three-phase ESS ====
+==== 7.3 Three-phase ESS ====
 A three-phase ESS system has at least one Multi installed on each phase. We recommend leaving the phase-compensation setting to its default: enabled.
@@ Line 717: / Line 818: @@
 A bit more detail with reference to selected modes:
-In __Keep batteries charged mode__ no power comes from the batteries to power loads unless the grid fails. PV power, when available, will always be used to power the loads.
-In __Optimize mode__ whether the load is great or small power will be supplied by the batteries. The Grid meter will be kept at 0W until either the battery is drained or the load exceeds the inverter's capacity.
+  * In __Optimize mode__ whether the load is great or small power will be supplied by the batteries. The Grid meter will be kept at 0W until either the battery is drained or the load exceeds the inverter's capacity.
+  * In __Keep Batteries charged mode__ no power comes from the batteries to power loads unless the grid fails. PV power, when available, will be used to power the loads. There is a known issue when using “Keep batteries charged” mode that can result in less production from the MPPT solar charger when batteries are full. This only occurs when [[https://www.victronenergy.com/live/ccgx:start#dvcc_-_distributed_voltage_and_current_control|DVCC]] is disabled, and the “Feed-in excess solar charger power” setting disabled.
+The current options to work around this "Keep Batteries charged" issue are:
+  * Enable [[https://www.victronenergy.com/live/ccgx:start#dvcc_-_distributed_voltage_and_current_control|DVCC]] (check CCGX manual to see if that is allowed for the used battery type, make & model!)
+  * Set the mode to Optimize, and set the minimum SOC to 100%. Note that with this workaround there is still a difference with the “Keep batteries charged” mode: the system will not recharge the battery from the grid after a power outage
 === Q2: I've enabled optimize mode, but do not see grid-power being used to charge the battery? ===
@@ Line 737: / Line 846: @@
   - Inverter shutdown through 'overload' when a large load is switched on
-With ESS in Optimize mode the system will always remain connected - even when the batteries are full. And although connected, the power draw is not substantial - yet this configuration offers the stability of the grid for nothing.
+With ESS in Optimize mode the system will always remain connected - even when the batteries are full. And although connected, the power draw is not substantial - this configuration offers the stability of the grid without additional grid consumption.
-=== Q4: Why is the VE.Bus state in //pass-through//? ===
+=== Q4: Why is the VE.Bus state in pass-through? ===
-In ESS, the conditions for the VE.Bus system to be in //pass-trough// are:
+In ESS, the conditions for the VE.Bus system to be in //pass-through// (ve.bus state: passthru) are:
-  * When the CCGX is no longer receiving data from the grid meter. Note that this is only for systems that are configured with an external grid meter. For systems without grid meter, see the Settings -> ESS -> Control without grid-meter setting.
+  - When the GX device is no longer receiving data from the grid meter. Note that this is only for systems that are configured to have an external grid meter. See the Settings -> ESS -> Control without grid-meter setting.
-  * Systems with a canbus-connected lithium system only: when the CCGX is no longer receiving information from the battery, via the canbus.
+  - Systems with a canbus-connected lithium system: when the GX device is no longer receiving information from the battery, via the CAN-bus.
-  * When charging the battery is not allowed (BMS max charge current = 0A, or max charge power = 0W) and there is excess PV power.
+  - When charging the battery is not allowed (BMS max charge current = 0A, or max charge power = 0W) and there is excess PV power.
-  * When discharge is not allowed (BMS max discharge current = 0A, or low SOC, etc...) and loads on AC-Out force the Multi/Quattro to exceed the AC input current limit.
+  - When discharge is not allowed -and- loads on AC-Out force the Multi/Quattro to exceed the AC input current limit.  Reasons for not allowing discharge: BMS blocks discharge (DCL=0), or battery SOC level is below the 'minimum SOC' setting in ESS, when SOC is at least 3% above the set level, discharge is allowed again.
+  - A grid code is in use that requires the enabling of battery discharging by aux-inputs. Check the used grid-code in VEConfigure and compare with the electrical signals provided to the Inverter/charger in its AUX inputs.
+  - The Loss of Mains detection (LOM) causes issues, often in combination with a high impedance connectivity to the utility. For details see [[ve.bus:grid-codes-and-loss-of-mains-detection|]].
 === Q5: How can I suppress low battery warnings? ===
@@ Line 768: / Line 879: @@
 === Q7: How do the charge states work in ESS? ===
-  * The MPPTs are always in the `ESS` state. This indicates that the MPPT is being controlled by the Multi or Quattro. To view the system state, look at the VE.Bus State.
+  * The MPPTs are always in the `ESS` state. This indicates that the MPPT is being controlled by the Multi or Quattro via the GX device. To view the system state, look at the VE.Bus State.
   * While discharging, and connected to the grid, the state can still show a charge state, such as Bulk, Absorption or Float. Even though it is not charging. This is normal, nothing to worry about.
   * When in Float, the system will begin a new charge cycle when the battery voltage has been below the restart-voltage for a certain length of time. This voltage depends on the chosen battery type selected on the charger tab in VEConfigure:
@@ Line 780: / Line 891: @@
 Switching off in overload, while connected to the grid, is caused by the active Loss of Mains (LOM) detection, linked to the country code as configured in VEConfigure3.
-This behaviour occurs when the AC supplied on the AC-in of the Multi or Quattro is 'weak'. By 'weak' we mean that the AC connection to the utility has a higher impedance than usual. For example a generator, or an old or remote house connected with a too-long and/or too/thin cable to the utility.
+This behaviour occurs when the AC supplied on the AC-in of the Multi or Quattro is 'weak'. By 'weak' we mean that the AC connection to the utility has a higher impedance than usual. For example a generator, or a house connected with a too-long and/or too-thin cable from the Inverter/Charger to the utility.
 For the solution and configuration options, see [[ve.bus:grid-codes-and-loss-of-mains-detection|]].
-=== Q9: Why does my MultiGrid refuse to feed-in? ===
+=== Q9: Why are my loads powered by the grid instead of battery or solar? ===
-A MultiGrid system can enter a state where feed-in (more precisely: converting DC to AC while connected to the grid) is disabled.\\ This happens when, at the moment of connection to the grid, there is not enough DC power to perform the required relay test. (N.B. this relay test is part of the grid code specification - and is mandatory). In order to perform this test the Multigrid must be able to run from battery during a period of time (depending on the selected grid code but usually about 1 minute).\\ If this is not possible, the system enters a //deadlock// situation (if no precautions are taken) as it will not be allowed to connect to grid.\\ Therefore the following exception is made: When the device cannot perform the relay test, it still switches to grid but will not feed-in. Once a minimum amount of time has passed (about 15 minutes) and the battery voltage has risen to at least 14V (for a 12V system) the MultiGrid assumes that there will be enough DC power to run from the batteries and it will automatically switch to Invert, then perform the relay test, and switch back to grid. Only then feed-in will be enabled again.
+Check list in case loads are being powered from the mains/grid, while expected to be powered from the battery:
-Therefore there is no need to worry - the system will resume feed-in automatically once the battery has been charged.
+__First of all__, check that the system is not preventing discharge because the battery state of charge is below a limit. See the [[#controlling_depth_of_discharge|Chapter 6 - Controlling depth of discharge]].
-=== Q10: My battery is first discharging, and then charged every night? ===
+__Secondly__, in case of a Managed Lithium battery, ie a battery with a CAN-bus connection, check that the battery hasn't disabled discharging: see the battery entry in the Device List menu, and then go to the Parameters submenu and see the Discharge Current Limit (DCL) entry. In case that shows zero, the battery is telling the system to not discharge any further.
-The recharge is part of sustain. Consider increasing the minimum SOC level. For example increase it with 5%; and then check what happens.
+__Thirdly__, feed-in may be disabled because the ESS Relay test is still pending: the inverter/charger (ie Multi/Quattro) in an ESS System needs to perform a relay test before it can use battery power. During the test, it needs to run in inverter mode shortly (~1 minute), and needs enough spare battery capacity to do so. In case the battery voltage is too low while connecting to the grid, the system switches on in pass-through and/or battery charging mode, and, while waiting for the battery to be recharged sufficiently (to do the relay test), it will not feed-in. Meaning that it will not convert DC to AC power, and hence will not power the loads from the battery, and similarly will also not convert any power coming from Solar Chargers to AC: will not power loads with DC-coupled solar power either. And the same: it will not sell excess DC-coupled solar power back to the grid.
+The relay test will be performed once either the battery voltage has been recharged above 14/28/56 volt, or when the battery has been recharged to above 20% SOC. To check if a system is in this state, see the ESS Relay test entry in the Advanced submenu of the Multi/Quattro entry in the device list. It will show either Pending, or Completed. Note that that menu entry is only visible for systems with an ESS Assistant installed.
+__Fourthly__, feed-in may be disabled when a grid code (like the German or Australian grid code) uses the aux1 input to disable feed-in, and aux1-in is used by something else (like an AC-sensor or a BMS), this way feed-in can be disabled. Simply un-check the option in the grid-code settings to prevent this.
+__Lastly__, check that the rocker switch on the unit is set to On, rather than to Charger-Only. When set to charger-only, the unit refuses to discharge the battery. Note that to check this, you really need to physically check the rocker switch: you can't see its state by looking on VRM or on the GX Device. On a MultiPlus-II, this rocker switch is at the bottom of the unit and needs to be in the I position, not on II.
+__Finally__, if all above didn't help - temporarily disable LOM to make sure that is not causing an issue. Detailes in this document: [[ve.bus:grid-codes-and-loss-of-mains-detection|]].
+=== Q10: Why does the system refuse to discharge my battery? ===
+See Q9.
+=== Q11: My battery is first discharging, and then charged every night? ===
+The recharge you are seeing might be part of the Sustain protection. Consider increasing the minimum SOC level. For example increase it with 5%; and then check what happens.
 Or decrease the sustain voltages with VEConfigure, but take proper caution, especially for lead batteries as the sustain levels are designed to prevent early damage to the batteries.
+Search this manual for Sustain to learn more.
+=== Q12: What is auto-recharge? ===
+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 the battery is recharged up to the Minimum SOC level.
+=== Q13: Can I use ESS in a vehicle or a boat? ===
+No, you cannot. After unplugging the shore cord it can take up a moment for the system to detect the loss of mains and open the back-feed relay. During those seconds, the shore power plug will be live: there is 110/230 Volts AC on the terminals. The exact number of seconds differs per country and depends on the local requirements.
+The same applies to other solutions where the wiring is not protected against accidental removing, for example a simple cable with end-user removable plug, such as a portable power supply.
+===== 10. Troubleshooting =====
+Trouble shooting steps:
+  - Start with checking firmware versions (needs to be latest). And when asking questions; report the exact firmware versions that are used.
+  - Check battery type/brand. If lead then it might be unsuitable and probably broken because of the heavy cycling.
+  - If some unknown or unsupported CANbus battery; change the battery to a supported type.
+  - Check the state of the inverter/charger, if its Passthru, then there is an issue. Details are available in Q4 in the previous chapter.
+Then; if PV is not used enough to power loads;
+  - Check for the # reason codes; see CODE KEY in this manual.
+  - Check wiring: lots of voltage drop between MPPT and multi will prevent the system from effectively powering AC loads from solar power.
+  - Test with and without SVS enabled: leave it disabled.
+  - Next, check MPPT charge current limit during the time that it is not used enough. MPPT CCL is supposed to be high always; even when battery full. Unless there is a temperature issue.
+  - Now check MPPT Charge Voltage Setpoint. It is supposed to be above actual battery voltage.
+Note that those last two set points are determined by software; and calculated based on the setpoints sent by the (CANbus connected) lithium battery: you can't change them manually. Looking at them however does help understanding why certain things are happening;
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