question

lucode avatar image

Trigger a dump load when your batteries are full (opportunity loads)

After browsing the docs and this forum for a while I’m still a bit puzzled about the fact that Victron doesn’t provide an easy way to manage opportunity loads. In this recent video it is said everything should be possible, but I couldn't find any information about how to do it. There seems to be no specific webinars in the professional portal.

https://www.youtube.com/watch?v=dT89QtG2pS4

relay assistant
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5 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Download the VictronConnect app and take a look at the demo library (for any smart devices).

You also download the VE.confic tool an use "Port selection -> Fake target with full options" to see the possibilities you have with a Multi (assistants).

What devices do you have? What do you want to achieve?

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Phil Gavin avatar image
Phil Gavin answered ·

I second this puzzlement, I don't doubt it can be done but in the face of several options, what is the recommended approach?

I also went hunting a specific webinar on the strength of this youtube video but to no avail.

A specific webinar is welcome and warranted.


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dayandnight avatar image
dayandnight answered ·

Hello @lucode, hello @Phil_Gavin

you brought up an interesting question. I found a way in combination with GX device. Here a small and old-style description, no video ;-) with text and screenshots of the way I did. It is possible to work with the programmable relay assistant and you have the possibility to select a certain SOC status for switching on a relay.

It works for me. But I had to notice by reading and interpreting the VRM portal that when SOC higher than 99% selected causes that the relay is triggered at SOC level in reality greater at > 99,5% so from understanding for to switch at 100% it is somehow a bit to early, which doesn't cause me real an headache.

The other switching conditions ...

... especially "Charge state" didn't help me ...

... because I was missing here the choice when "full". My battery is a lithium pylontech which built in BMS. So as far I understood bulk and absorption is more a "historical" ;-) status for lead accid batteries and not real usable for me.

I use a combination of several relay assistant to control my PV Aeconversion micro inverters to control PV power output and in case an EV car is waiting to be charged that charging process is started at this status when batteries are full which is equal in understanding SOC level is higher than 99,5%.

My system is a 3-phase system with three pieces of Multiplus-II and each Multiplus-II has its own relay outputs and can be driven individually by different switch conditions. So there is high potential even to do complicated AND / OR combination by using relay hardware as well with combination with the software assistants.

From the standpoint of view of hardware I use small 12V relay interface from finder series 38 witch needs only a few mili-amps and can be directly driven from my Multiplus-II device without an additional power supply. It is specified to drive up to 100mA. I connected the contacts directly to the coil contacts of my relay. Of course there are many other brands for relay which can be used here as long they need lower as the 100mA maximum coil current.

A Multiplus II, has "real" relay contacts as well which can be used directly for switching a load. I don't know the spec for this contacts, but I think it is always recommended not to switch here directly a heavy load On and OFF as relay contacts has to be understand in such circumstance somehow as consumables and when the internal relay contacts are gone it is expensive and complicate to do an replacement.

Perhaps this information helps you and put you on the road for possible solution.

DayAndNight


2 comments
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Thank you, for that lengthy description. That would indeed seem to be one alternative.

I suspect there are a few others, the objective is to ensure that useful power is not lost by the MPPT's throttling.

One would then like to choose whether to export AC power to the grid or to utilize it in-house. (or some combination).

Some third-party MPPT's even have the capability of a PWM output that can control an SSR and incorporate DC resistive loads direct off the battery.

Wind generation by necessity has to incorporate dump loads.

My point is there are quite a few options with associated pro's and cons, it would be nice to have a webinar that dealt with the topic comprehensively.

Thank you @DayAndNight for your detailed answer. I will have a deeper look at your solution. My solution so far is to use the Generator Start/Stop function on the GX the opposite way. It is a bit quirky to set the params but it works fine with a connected NC 16 amps relay. (I have to invert the GX relay contact too.)

lucode avatar image
lucode answered ·

Thanks for the many tips and tricks.

Having a on Grid system with ESS build with a EasySolar 5000.

After browsing the docs and this forum for a while I’m still a bit puzzled about the fact that Victron doesn’t provide an easy way to manage opportunity loads. In my humble opinion individual load management is a crucial need for most self consumption on- or off grid installations similar as the sophisticated charger and inverter control system ESS does provide quite well.

I did create some specs about a possible load management solution that should fit for most of the use cases. BTW Fronius comes with such a solution since quite a while.

Victron_LMS_Specifications_v2.pdf


1 comment
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The Loan Management System screen could look like this mockup:

insanesplash avatar image
insanesplash answered ·

I managed to do this using a contactor, Sonoff Mini and using the Venus GX Relay 1 (Generator). Its a bit strange though to see the generator time ticking away when the system is not 'dumping' a load, and marked as stopped when it is.

I have also looked at the Multi+ Assistants to do this as an alternative but as the Venus is more "aware" of the SOC of my batteries from the BMS than the Multi+, I'd prefer to have this relay managed by the heart of the system directly.

In summary the system works in reverse...


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