I install systems primarily on RVs and Vans. With the greater availability of batteries with Victron comms using DVCC has become an option more often than it used to be. I have personally received mixed opinions from other professionals on the worth and reliability of using DVCC versus just sticking with a smartshunt or BMV. Sometimes I get the feeling that they are making an excuse because they are not trained or confident in setting up a DVCC system. However there are other installers who I consider much more advanced in their knowledge and experience who also give mixed opinions on DVCC.
I would like to hear some opinions, especially from those of you building smaller off grid type systems about pros and cons of setting up DVCC in a small power system.
Maybe present what the issues are believed to be? Far easier to demystify perception than to try convince people why it works.
Itās function and use-case is clear, and smaller mobile use isnāt different to smaller off-grid or even domestic implementations.
If this forum is anything to go by, DVCC is often blamed for many things which mostly are rooted in ignorance, poor config/installation or simply not playing nice with DIY implementations or customisations.
In a certified and tested environment it just seems to work.
In environments where someone does not want to follow best practice or have defined their own - often influenced by the internet - then it can appear to be going against the behaviour they are trying to force the system into.
Remember, its purpose is simply to coordinate charge sources and provide a set of common references and/or shared limits.
I completely agree with āāNāickās assessment. When you have a clear understanding of your requirements and how to properly configure the system, DVCC is highly reliable. Unfortunately, there is a significant amount of misinformation being shared by those who may not fully grasp the technicalities involved.
As Nick noted, if installers choose not to follow established best practices or attempt to define their own without a solid foundation, they cannot expect optimal results. Sticking to proven standards is essential for the reliability and performance of your systems.
I am an off-gridder and never had any issues in my 12v or 48v systems.
I completely agree with Nick and Dave on this. I would also like to add that after installing and operating systems with DVCC enabled for several years, I have found it to be consistently rock-solid and reliable.
Much of the skepticism usually stems from non-compliance with best practices or the use of incompatible third-party components. When following the official documentation and using supported hardware, DVCC is not a point of failureāit is the essential integration layer that ensures the system operates as a single, synchronized unit.
In smaller systems, it effectively coordinates all charge sources and provides a set of common references. By enforcing shared voltage and current limits based on real-time BMS data, you eliminate the ātug-of-warā between chargers that often occurs in manual configurations.
I wouldnāt build a modern lithium system without it.
In my view enabling DVCC is a layers of protection issue if the battery BMS is capable of controlling charging then you have the best source to control all charging as one at the required voltage and current. If this fails then you have the charger settings to take over, so you have two layers of protection. It also eliminates the chance of incorrect charger settings from wrongly charging batteries, perhaps pushing to cell over voltage shutdown. Additionally, if the BMS needs additional absorption time for balancing, using DVCC allows this, if the cells are balanced absorption can be a few minutes. Not using DVCC means you are always running to a fixed absorption. On RV and boats this means that shorepower may have your batteries at 100% on float, then solar starts and gives you a fixed absorption if you do not have tail current as end of absorption, then you start the engine to travel and the alternator then gives you a third period of absorption on already full batteries.
My boat has Victron NG batteries with the Lynx NG BMS, solar, Multiplus, Wakespeed WS500. DVCC is forced on but I would not be without it.
These are all excellent responses and just the confirmation I was hoping for. The criticisms I have heard before are that a smartshunt or BMV are more accurate than the BMS or general statements that DVCC is buggy and not reliable.
Certainly some BMS boards, especially some at the cheap end of the spectrum have a reputation for inaccurate SOC, which means a SmartShunt may be useful, but you can still have the BMS controlling charging via DVCC and use the SmartShunt just as a battery monitor.
Dvcc seems ideal to provide global charge limits in cases where you want to limit charge rate on smaller battery systems. However it doesnāt take general dc loads on the power bus into account which may or may not be a problem.
Iāll throw in some anecdotal evidence, as an installer and a full-time RVer who has had full Victron systems in my last 3 RVs. DVCC works great as long as you configure your gear properly.
I think @pwfarnell makes a very valid point regarding the complexity of these integrations. To build on that, a crucial part of a reliable DVCC setup is actually what happens when the communication fails.
In my experience, a system is only as good as its fallback plan. If the GX device or the BMS communication is interrupted, the individual chargers will immediately revert to their internal local settings. If those settings are left at defaults or are too aggressive, the system loses its safety margin the moment DVCC isnāt there to coordinate.
I always find it best practice to manually program each MPPT and Inverter/Charger with conservative āfallbackā values. This ensures that even if the ābrainā of the system goes offline, the hardware remains within safe limits. Itās not just about getting the DVCC configuration right; itās about ensuring the system is inherently fail-safe when it has to run stand-alone.
If you lose a GX the system will effectively stop.
Solar chargers that are under BMS control will power down with a BMS lost (error 67) alarm.
There is a short timeout to allow for maintenance but after this the alarm will trigger.
Err 67 - BMS Connection lost
This error shows when the charger is configured to be controlled by a BMS, but does not receive any BMS control messages. In that situation, the charger stops charging by reducing its output voltage to the battery base voltage (12V/24V/36V/48V). This is a safety mechanism, the reason to still enable the output is to allow a system to self-recover from a battery low situation.
Solar Chargers only show this error when there is solar power available and thus the device is ready to initiate charging. It does not show at night. And in case there is a permanent problem, the error will raise in the morning and clear at night, and so forth.
DVCC is definitely a good way to provide more detailed battery information and more accurate battery management than the simple ātotal battery voltage/currentā that you get with a smartshunt or the inverter battery measurement.
However, you are now reliant on the behaviour of the BMS in the battery, and they donāt all work the way Victron says they should.
The biggest advantage of DVCC (IMHO) is that you get individual cell monitoring so if any cell gets to too high or low a voltage the control system is informed. This is less reliable when using an overall voltage measurement, especially as batteries age and variation between cells increases. And the more cells there are the more this makes a difference (so more significant for 16 cells (ā48Vā) then 4 cells (ā12V).
However DVCC does not interact correctly with MPPT controllers if the BMS uses current limits, rather than voltage limits when the pack gets full. And many do. This is explained in this thread here: MPPT Charger stops generating, excess DC PV not being feed-in
So if you have a BMS that does this, and an MPPT controller, and a system running in ESS mode that can export (my situation), then DVCC will not work for you. In small vans systems where there is no export, this issue may not matter. (There may still be issues with topping-off balancing current being curtailed early - Iām not sure about how this works in practice on non grid-connected systems).
This is actually a specific issue relating to charging and PV inverters on AC IN.
It has nothing to do with DVCC.
Setting CCL to zero is problematic for controlling charge. It is an easy (lazy?) way of dealing with a problem and while the system will try honour that, it just isnāt always possible.
Charging should be controlled via voltage.
In the link provided this is also an unsupported battery.
When batteries become supported, they have gone through a test cycle to show they behave as expected, even without voltage control.
So again, donāt blame dvcc for misbehaving with untested or customised systems.