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pcg asked

DVCC with a VE.Bus BMS and Cerbo GX

I’m exploring options for using DVCC to protect a Li Smart battery. I know that I can use a Lynx Smart BMS in conjunction with a Cerbo GX to do this by connecting VE.Can on the Lynx Smart BMS to BMS Can on the Cerbo GX, and enabling DVCC in the Cerbo GX.

Can I do something similar with a VE.Bus BMS? In searching for the answer, I came across this statement in the CCGX manual… “DVCC can be used without any problem. The same is true for Victron Energy lithium batteries with the VE.Bus BMS”. However, the VE.Bus BMS manual makes no mention of DVCC, and it’s not clear to me how one would connect the VE.Bus BMS to a Cerbo GX to allow this. Would one connect VE.Bus on the Cerbo GX to the connector labeled MultiPlus/Quattro on the VE.Bus BMS? I have no inverters in my system so I’m not using VE.Bus for anything else.

My end goal is to have the ability to control an MPPT 100/50 which is connected to a Cerbo GX via VE.Direct. Since the MPPT 100/50 only has one VE.Direct port, I don’t have the option of controlling the MPPT 100/50 via VE.Direct with a non-inverting remote on/off cable.

DVCC
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pcg avatar image pcg commented ·

And in case anyone is wondering why I don't just use the BMS to disconnect the output of the MPPT with a Cyrux-Li (instead of turning the MPPT off), the reason is that I'm concerned about damaging the controller with a voltage spike caused by discounting its output while it's charging. Is this not a viable concern?

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Kienan avatar image
Kienan answered ·

UPDATE

There is a new product now, but it will be closer to what you need. This new product surprised me, it's the VE. Bus BMS V2. I left my original answer below, this top part only applies to the V2 BMS. Read down to the original answer for the original VE. BMS.


There are several differences between the original and the V2, but the biggest is that the V2 can communicate directly to a GX Device.


So this new V2 BMS will absolutely control the charge controllers through the Cerbo GX VE. Direct cable. I fully read the manual, and I recommend that you read it here - https://www.victronenergy.com/upload/documents/VE.Bus_BMS_V2/VE_Bus_BMS_V2_-_Manual-en.pdf


The only thing I'm not certain about is if you could get it would work without a VE.Bus Inverter or inverter/charger. One thing you have to know in order to make it work is that the V2 is intended to get it's battery negative from the inverter, so, you would need to do is take a UTP cable (ethernet cable) and cut it open and trace out which wire connects to pin 3 (GND), and connect that to the battery negative. Plug that into the MultiPlus/Quattro port on the BMS and that will allow the BMS to power up. I have used the V2 BMS in this configuration and it works for controlling the ATC and ATD terminals. The only question is if it'll communicate to the Cerbo when you connect the Cerbo GX to the Remote Port on the BMS. I have not tested that yet, but I will on my bench when I get a chance.





Original answer, applicable only to the original VE. Bus BMS.


The original VE.Bus BMS cannot communicate with any GX device, it is only designed to communicate with an Inverter/Charger. You can use DVCC to limit the maximum charging current, and voltages, but it would not be informed by the BMS, it would be programmed in advance. I'll demonstrate why you might want to do that below.

This paragraph is not directly related to your situation, but it still may be helpful... Someone may ask, "What if I do use an inverter/charger, couldn't the BMS communicate with the inverter, the inverter communicates to the Cerbo GX, and the Cerbo GX DVCC work off of that?" The short answer is no, Victron has not set it up that way. I'm not 100% sure why but I think I have a good idea. To understand why, you need to understand one crucial thing... Whenever communication with a BMS is lost, everything must shut down. Nothing is allowed to charge or discharge a lithium battery if the BMS is not in control. So, if the inverter were to shut off, communication would be lost, and the whole system would shut off, so the charge controller wouldn't be able to charge the batteries. So if the batteries got low enough that the inverter had to shut down, the charge controller would have to shut off because of a loss of communication with the BMS. You'd never be able to turn off the inverter and simultaneously allow the battery to charge.


So why might you use DVCC when you have a VE.Bus BMS if the DVCC can't be informed by the BMS? There are cases where the sum of the charging sources could exceed the maximum charge current for the battery, and you could use DVCC to limit the total charge current. An example would be if you have some solar on an east-facing slope tied into one charge controller, and some on a west-facing slope on another charge controller, and at noon, their combined maximum output may exceed the maximum charge current rating of the battery. You wouldn't want to limit the individual charge controller limits because in the evening, you want the one charge controller to put out more than 50% and in the morning you want the other one to put out more than 50%. Another example is if you have an inverter/charger and solar, and the combined total of the charge current from the inverter/charger and the charge current from the solar could exceed the battery charge current rating... the DVCC could protect the battery from them combining to too high of a charge current.

In any of these cases, each device still needs to be controlled by the BMS, and in the case of the SmartSolar 100/50 or BlueSolar 100/50, the officially recommended method is using the BatteryProtect 65A. Something like the Cyrix Li would work just as well. This does not void the warranty, you don't have to worry about voltage spikes. Victron builds their charge controllers to be extremely robust. This would destroy an Outback charge controller or many other brands (I watched an Outback FM80 destroy itself once when it wasn't connected to a battery), but this is the officially recommended practice for the Victron charge controllers.


Does this all make sense?

Thanks,
Kienan

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dwmarine avatar image
dwmarine answered ·

The VE BUS V2 might do what you want.

I've got one on order to see if it will control my solar controllers via VE Direct.

From the VE Bus V2 datasheet:

"Disable charging in VE.Bus inverters or inverter/chargers via VE.Bus, disable VE.Direct and VE.Can solar chargers via a GX device and disable other chargers via the 'Charge Disconnect' terminal in the event of a cell overvoltage, under temperature or over temperature condition"


Darren

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