question

Jürgen Scharfe avatar image
Jürgen Scharfe asked

Virtual Switch control with Aux-1 and Aux-2 instead of using assistants

Why don't you integrate the Aux-1 and Aux-2 inputs to control virtual switch.
VS is an easy and reliable method for DC coupled solar system.

The Ignore AC with dedicated gen control would even allow to control the MPPT in case of a Battery / Cell full signal withuout any other external relaying

Assistant are a pain because
- documentation is fairly poor
- every time you want to adjust a parameter in the assistant ( e.g. a threshold ) a running system goes black when assistant is charged
- all conditions are OR connected, it is a pain to program an AND condition for interlocking
the only way seems to be inverting every input and the output which makes things difficult to read and is error prone



Multiplus-IIBMSvirtual switch
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4 Answers
boekel avatar image
boekel answered ·

What exactly do you want to accomplish?

I agree documentation can be better, but it is a very powerful tool.

Normally an installer programs the units for life, only changing settings when the system is changed. End users should not change settings in complicated systems, on risk of warranty voiding or even dangerous situations.

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Jürgen Scharfe avatar image
Jürgen Scharfe answered ·

Thank you for that quick answer !

You are right - Assistant are powerful.

But there are basically three inconveniencies:
1. you cannot do fine adjustments online becausse every adjustment in assistents requires a shutdown.
2. programming could be more straigthforward if AND conditions would be possible not just OR

Is there any other to combine two conditions in1 and in2
out = not ( not(in1) or not(in2) ) = in1 and in2

3. why no not simply use scripting ? Such as "IF UDC < 50.4 then GenFlag = On"
Behind the user interface, assistants are probably nothing else

My system is a simple dc coupled solar priority system with no feed-back to grid . Worked fine for years .
I have replaced my multiplus 24/3000 by a multiplus II 48/3000 re-arranged the battery for 48V/360Ah and just wanted to set-up virtual switch with the two contacts for the BMS - no quick setup because AUX contacts are not in the listed in the VS configuration A and B page

Unfortunately I could not use the virtual switch and had to replace it by assistants. Works fine now with one set of conditions to set and to reset general Flag
Finally I managed to set up using 2 relay assistants but found it quite time consuming.

Best Regards

Jürgen

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boekel avatar image boekel ♦ commented ·

remember that 99% of users never use any assistant, if needed it is setup by installer. So for an installer to have a learning curve it is ok.

What an 'advanced user' like you will probably like is Node-Red:
https://community.victronenergy.com/questions/549/feature-request-scheduled-virtual-switch-for-venus.html

From what I have gathered the assistants will not be changed more than needed, as advanced functions are bound to be done with node-red and other options in the Venus system.

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boekel avatar image boekel ♦ commented ·

btw, did you find the 2wire BMS assistant? specially made for this functionality.

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screenshot-2019-04-12-220327.png (20.8 KiB)
Jürgen Scharfe avatar image
Jürgen Scharfe answered ·

Hi Boekel,

Yes i know of this assistant and my got ideas to prgram the relay assitants accordingly

SOC does not work anyway with a MPPT charger ,

I am using the programmable relay to stop the MPPT when BMS sends a "cells full signal" to stop charging

I will try to allow Multiplus to do some emegency charging only if low cell alarm is on but need more study to program this using the charge current signal on the Aux2 perhaps ....

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boekel avatar image boekel ♦ commented ·

the BMS signals should only be active in emergencies, normally the charge / discharge parameters of all devices should stay clear of the alarm levels.

I'd use battery voltage as setpoints to do what you want.

BMS signals are to stop inverter / mppt from charging / discharging but are only for emergency

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solartech12 avatar image
solartech12 answered ·
sounds very promising , can you share few details about it :)
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