Operation of victron multiplus inverter when below freezing

[wmcneil]

Ohiobrits, thank you for the detailed information. There are many details that are not in any of the documentation that I can find on the Victron web site, so one has to fill in the missing pieces by digging around, and your detailed explanation of how the assistants work filled in another piece of the puzzle. I am glad to hear there is robust software capability to enable use of the general purpose aux inputs and relays.

[fran&frank]

Thanks everyone for this great discussion. I'm going to try to summarize what I heard just to get it straight in my head. You can use the temperature sensor for the BMV-702 with the BMV-702, and connect the BMV-702 by a positive and negative wire to the auxilary inputs (which I think are referred to as V sense plus and minus in the Multiplus manual), or to the Temperature sensor plus and minus inputs re-purposed for this purpose, and program a charge assistant to turn the charger on and off with freezing weather. However, it is apparently not possible to use the temperature sensor that comes with Multiplus connected directly to a temperature sense input on the Multiplus for this purpose. --Frank

[wmcneil]

Originally Posted by fran&frank

Thanks everyone for this great discussion..... --Frank

The Vsense_plus and Vsense_minus are not the aux inputs. There are two pairs of aux inputs, which are named Aux_input_1_plus / Aux_input_1_minus, and Aux_input_2_plus / Aux_input_2_minus. The Voltage_sense_plus / Voltage_sense_minus inputs may be connected directly to the battery terminals, if you are concerned that the MPlus is not getting an accurate enough voltage reading from the Battery_plus /Battery_minus connections(this would only be due to IR loss because you have not sized the wires large enough.)

[fran&frank]

Thanks for that correction Bill-- Frank

[wmcneil]

Originally Posted by Ohiobrits

wmcneail,

The inputs on the MultiPlus can be configured to do many things using assistants.....

Ohiobrits,
I would like to turn off the Mplus charger based on using the BMV-702 to signal low temperature to a pair of Mplus inputs (Either Tsense, or Aux1, or Aux2). It looks like one way to do this would be to use the Programmable Relay assistants to manipulate the General Flag, and then use a General Flag User assistant to respond to the General Flag state and control the inverter. I have a couple of questions:
1) Does the selection of available actions in the General Flag User assistant include controlling the charger?
2) Does use of the Programmable Relay assistant require that you control one of the Mplus general purpose relays?

Thanks!

[Ohiobrits]

wmcneil,

I have not used the General flag feature but it looks like there is the following functionality:-

The options for the General Flag assistant is shown in the first graphic below. To answer question 1, you could set up the General Flag to ignore AC1 (which would turn off the charger) but this would also remove AC power from other users which is probably not desirable.

The Programmable Relay Assistant can set the General Flag based on input states on various inputs such as Aux 1 (see graphics below). I think you would need to set up 2 Programmable Relay Assistants one to turn the flag on and one to turn it off.

By the way, you can download the software on the page linked below and have a play. You will be able to see all the Assistants and options available without a password. You just can't load a configuration with Assistants without the password. The Virtual Assistants I believe you can use without a password.

Enjoy!

https://www.victronenergy.com/suppor...e-bus-products

[wmcneil]

Ohiobrits,
Thanks for the details. From the pictures you posted, it looks like the General Flag User assistant does not have the ability to control the charger by itself. I tried downloading the VE configure software, and when it loads, I get a message stating "From this VECconfigure version onward, a password will be required to unlock the assistants features and be able to work with assistants." The help available with the software has no more information that what is available online. Victron has a little bit of documentation about the various assistants online, but it is not enough to understand what all the capabilities are.

It is becoming clear that Victron does not want we mere mortals to have access to full documentation. I have spent a fair bit of time researching their products, and I am beginning to loose my patience with the difficulty in getting the answers I need to make a decision about a very expensive system purchase. I am an electrical engineer, and I will not be paying someone to install a system, I will be doing it myself. Perhaps once one makes a decision to go ahead and buy from an authorized dealer, maybe one can obtain access to better documentation? Or maybe not?

Are you turning off the Mplus charger based on temperature, and if so, how are you doing this in your system?

Thanks again.

[wmcneil]

I made another run at using VE configure, and by doing "Port Selection" / "Fake Target with full options", I was able to add the different assistants and see the options. Looks like the Charge Current Control assistant can be used in conjunction with Tsense or Aux1 or Aux2 to turn off the charger.

My patience has grown a little thicker

[lsbrodsky]

Yes, charge current control, in conjunction with T-sense and the optional temp sensor provided for the BMV 702. If you buy your stuff from AM Solar, you will get all of the help you need. They will provide the Assistant for you or answer your questions about setting it up. When I had questions early on, Victron overseas referred me to my selling dealer, so I suspect the model is that the dealer has the information you seek.
Larry

[wmcneil]

Originally Posted by lsbrodsky

Yes, charge current control...
Larry

Larry,
Thanks. When the time comes to buy, I had been leaning toward AM Solar, and it's good to know they provide full support.

Bill

[Troutboy]

Bill. I also purchased from Amsolar. They have been great thus far. Also, Larry has gone through this months before me so he has learned a lot and is sharing lessons learned which has helped me avoid some of the time consuming issues he ran into. With two of us (and others) going through this, just ask questions. We all will help.

[Ohiobrits]

Agree with all the other posters - buy from AMSolar. They were great to deal with and helped me with my assistants, wiring diagram and other general help even though I bought just the main building blocks and not one of their kits. Good customer service indeed.

wmcneil - go with Victron! You will not be disappointed. As far as I can see they are light years ahead of anyone else when it comes to truly integrated solar / inverter / charger systems in particular with regard to monitoring / viewing status and automation.

As others have said - if you need help - ask.

On the question about turning the charger off based on temp. In my case, the BMS charge enable pin pulls to ground when charge is permitted. It determines if charge is permitted based on state of charge, battery temp (both low and high) and several other realtime measurements of voltage, resistance etc of each cell. I have 12VDC connected to one side of a standard automotive relay coil and the BMS pin to the other. The BMS energizes the coil (by pulling to ground when charge is enabled) which closes the relay switch and "closes" the Aux 1 input on the MultiPlus. Charge is now permitted. Conversely, if charging is not permitted (low temp), the charge enable pin floats high, the relay coil is de-energized, the relay switch and the Aux 1 input open and charge is prohibited.

Easy......right

[wmcneil]

Thanks everyone for the input on AM solar, and the details of your implementations. I've got most all of the info I need. The hardest part remaining is finding time to do the work.

[fran&frank]

Recently did some cold weather camping and was able to verify that the charge control assistant I programed on my multipluss 3000 and the low tmerpature relay on my BMV702 all worked as they should and did not allow charging of my lithium battery below the temperature setting for the low temperature relay on the BMV--which I set at 35 degrees. I also had a pleasant surprise when I discovered the Victron mppt 100/50 had a built in low temperature cutoff that works when temperature is avaiable from the BMV and is preset at 5 degrees C. I thought I was going to have to disconnect the mppt manually or rig up some other electronic disconnect for cold weather-- but its aleady taken care of and set up by default.--Frank

[waninae39]

no issues

we leave it on all year round

on the power side we swap out the lion and but the lead acid in

everything is fine