Reasons why a Victron Energy System will not charge batteries

To start charging batteries from 'empty', the ZBM2's inside each ZCell need a sustained 55V (or more) in order to start up, perform a 5 minute 'bubble purge' and then a 'pre-charge' process (in which the internal electrode stack voltage is raised smoothly from 0 volts up to 55 volts).

If your system isn't charging batteries - if the voltage shown on the BMS status display is circa 36-40 volts and/or if the CCGX status page says 'Sustain' and doesn't start to charge batteries, read on.

Note that a clustered system - especially a high-power clustered system - connected to a small number of ZCell batteries - can be more problematic to 'boot' compared to a smaller or single-unit Victron installation. The Victron charge controller is relatively 'gentle' and sometimes it seems to take a long time to decide to raise the charging voltage. Hence step one is actually 'be a bit patient'...!

If you are using ESS (e.g. on-grid solar-self-consumption site), start by making sure the issue isn't simply that the Victron environment isn't currently ready to charge.

ESS won't charge batteries until there is a reason to do so - normally this reason is a surplus of solar energy over and above on-site loads (ESS by default won't charge until a surplus exists to charge with). 

Note that this can be over-ridden with ESS to start charging in various ways, including:

• Using the ESS menu 'keep batteries charged' setting to force charging to start (before returning to the normal 'Optimised (Without BatteryLife)' setting)
• Raising the value of MinSoC on the ESS menu (but note this should not be above 0 on single battery systems as per the installation instructions)
• Using the Scheduled Charging function in the ESS menu to set up a time when batteries charge 'from grid' regardless of solar conditions

If one or more of these conditions is being met or if ESS is not installed (off-grid system) so it is not 'obvious' what the problem is - then - read on for some ideas.

There are some other reasons why a Victron Energy system won't charge batteries, that applies to Redflow and non-Redflow systems alike (and hence can affect Redflow systems).

We've listed the main reasons below - check down this list and its likely you can get your site charging again!

(Each of these has been shown to be 'causal' in at least one site in our experience so its worth checking all of them before trying harder to find another reason)

Old firmware in the Multi/Quattro system

• Upgrade to the latest released firmware and try again

Old ESS Assistant version in the Multi/Quattro system

• Upgrade to the latest ESS Assistant version and try again

The DVCC system is not turned on

• Turn it on under the System Settings page in the CCGX and ensure that the BMS connection is shown as 'on' at the bottom of that same page. If not, re-check the CANBus connection and configuration of the system.

The DVCC SVS function is turned on

• This function does not currently work well with Redflow environments (with a specific exception - see below!). Turn this setting off for stable voltage control over time

An External Grid Meter is configured on the ESS menu but the grid meter is not connected

• If an External grid meter is configured into the system (which is required if you have AC loads on the 'grid' side of a Victron deployment along with grid-side AC solar) and if the grid meter becomes disconnected for any reason, the Victron Energy system will 'silently' fail to charge the battery system, no matter what settings you change to try to make it charge.
• This issue is subtle, because in the Victron Energy ESS software (at the time of writing) there is no on-screen error message and no other direct indication that the grid meter is 'configured but not connected' (i.e. that the grid meter connection has subsequently failed)
• When this condition exists, the system still shows values for the "GRID' and "AC Load" measurements on the on-screen graphical display... It is just that those values are wrong.
• This fault can be verified remotely by setting the ESS 'Grid Metering' value to 'Inverter/Charger'. If the batteries then start charging, this is your issue. But if you need a grid meter, this is not a fix, it is only a diagnostic confirmation. You need to fix the grid meter and configure it back in.
• You need to figure out why the grid meter isn't working...and fix it (so that the grid meter line appears on the main GX text menu and so that if you select that menu item, you see valid values for grid measurements from that device).
• The loss of grid meter access can be for many possible reasons, including a physical cable fault/disconnection, a ground differential issue between the USB dongle and the GX (best solution: use an isolated RS485 dongle instead of a standard FTDI unit), or the meter itself having failed.

A blown DC fuse or other DC energy path fault exists between one or more Multi/Quattro cluster members and the batteries

• This one is (also) subtle
• If the DC voltage measured by the Victron environment is incorrect then the system won't raise the voltage and keep it raised - it will cycle up and down, 'hunting' instead of being a stable voltage source. 
• The DC voltage measured by the cluster is from the L1 master (only).
• If there is blown DC fuse or a hardware fault in a cluster member other than the L1 master, then the system won't start up because of inconsistencies in voltage measurement between multiple cluster members
• If that L1 master has a broken DC path between it and the batteries, then its own self-generated 'sustain' voltage will be measured back by that unit instead of sensing the real DC bus voltage. In effect the unit will 'see its own shadow'. That voltage will not accurately reflect the real DC bus voltage
• This class of physical DC path or Victron hardware fault cannot be sensed via the CCGX menu system - which shows only the L1 master DC measurement (correct or otherwise).
• If this is a suspected issue, measure the physical system elements directly to ensure that all cluster members have got operative DC paths between batteries and the shared DC busbar to which all devices are connected.
• If a system is remote and cannot be immediately inspected, one thing that can be tried (despite the previous advice point!) is to turn SVS mode on. This is because SVS mode 'trusts' the voltage measured via the BMS from the Redflow batteries in preference to its own internal voltage measurement.  Sometimes, turning this on can be effective to 'boot' a system remotely in the first instance. If this approach does work, and if all the other approaches above (especially firmware updates) were not effective, it is well worth a site inspection and/or hardware checks as the next diagnostic step.

Redflow battery electrolyte temperature is too high

The Redflow BMS will stop charging (by sending a "Charge Current Limit" of zero via CANBus) if any battery reaches a threshold temperature (Default: 45C) at which charging should be suspended.

It does this in order to try to avoid the battery electrolyte temperature reaching the absolute 'shutdown' electrolyte temperature (50C).

If the 50C electrolyte temperature level is reached, the on-board battery controller will physically unplug the battery to protect it from further charge-driven temperature rise. This also results in the loss of access to the battery energy for the rest of the system (with obvious site-shutdown risks for off-grid sites).

The default charge cut-off temperature the BMS, 45C, is a level which should not be reached during routine charging operations in normally ventilated battery sites. The point of halting charging at 45C is to try to keep the battery from reaching 50C and unplugged (as noted above). 

If your site routinely reaches an electrolyte temperature of 45C, you need to take steps to stop that happening - by doing what is physically necessary to lower the air inlet temperature to the batteries to a level that allows the battery to keep its electrolyte temperature adequately controlled.

Those steps generally just involve increased/improved external fan-forced air ventilation, but in sites where the external inlet temperature cannot be kept below the high 30's, it may become necessary to implement active cooling of the battery room (e.g. reverse cycle air conditioning or similar).

Other possible causes

It is worthwhile consulting the Victron Energy FAQ item 10.4 for further reasons why a system may go into 'Passthru' state (resulting in batteries not charging and potentially no battery backup if the grid fails): https://www.victronenergy.com/media/pg/Energy_Storage_System/en/faq.html