question

tr0y avatar image

Multipluss Recreational Vehicle application / Solar DC first then AC from shore by SOC or Voltage ?

Looking for guidance on how to prioritize DC / Solar / Battery in a mobile application.

I am looking to minimize costs when plugged into shore power. I would like to use my PV array to run the majority of my loads down to a voltage set point or SOC and once that threshold is crossed have the backup AC power kick in to run loads and if need be recharge batteries.

My system is a Multiplus 24/3000, Midnite solar 150 Charge Controller, 5.5KwH Tesla Module 1600 Watts of PV on the roof, and assorted other parts.


I looked into assistants and ESS but those look to be more of a stationary grid tie application, maybe I am wrong ? I am new to Victron equipment but not new to solar and the related gear.

Can anyone steer me in the right direction ? Thanks !

Lithium Batteryoffgriddc system
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3 Answers
wkirby avatar image
wkirby answered ·

I'm not certain, but there's probably a way to use the relay in the Classic to command the MultiPlus to ignore AC until required.

The Classic will need a Whizz Bang Jr in order to know and be able to act on SOC. It's probably possible to set the Classic relay to act on Voltage, but this is a vague way of determining SOC.

I'm a bit rusty when it comes to Midnite equipment. I should dig my Classic 150 out and firmware update it to see what's new.

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Thanks @WKirby I do have a WhizBangJR running so I have a reasonable SOC monitor.


JohnC avatar image
JohnC answered ·

Hi Troy. There's possibly other ways to do this too, and depends what you want.

Firstly, a simple way to prioritize pv is to set your Midnite's charge parameters slightly higher than the Multi's. They'll both produce to capacity while under those (with a risk of overcurrent to the batts), but the Multi will back off first once they're reached. You can also limit ac input to the Multi, and in a simple system that will include both charge and load currents.

You could also look at Virtual Switch and/or Assistants for the 'generator start/stop' function.

There's plenty features in there, but to access them will likely require a stepup with extra kit to do it. A GX box is recommended, sure it costs $$, but give it some www and you'll see money well spent. Might be a few other bits'n'pieces too, and a BMV could mostly substitute for the Midnite's lack of compatible comms.

I personally prefer to switch in my ac backup (a generator) manually, but you can surely achieve what you want somehow.


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Thanks @JohnC I have the option of generator or actual 120AC from a home. I am surprised that this inverter has no real setting to just say AC or DC priority to X. My previous inverters could do this with the literal flip of a switch.

In this system I really have to watch overcharge situations as I am running a Tesla module as battery and over current there can get ugly very quickly.

I do have a Venus GX and a BMS 712 ( was hoping to not need it ). Victron just sorta bleeds you dry on extras to get functionality and of course the total lack of support if frustrating. I appreciate the community aspect of this forum but at top dollar prices, I am seriously disappointed in Victron. I called Magnum with this same issue and it is about a 30 second change. Anyone interested in a 45 day old 24/3000 MultiPlus ?

Sorry Rant Over ...


Paul B avatar image
Paul B answered ·

Hi Troy

I would be tring to use the ESS as this does what you are looking to do quite easly.

if a generator is involved then you have to be carefull that power is NOT exported back to the generator. but as you are using DC coupled I cant see a issue there.

you may have to change the Solar Reg add BMV 712 and install a CCGX or Venus Gx so that full management can be achived, if you dont change the solar reg then you would have to use the BMV to control the solar side, and this should be posable if you use the SOC in the ESS tied to the BMV as the master battery monitor.


the ess is not recomended for this but that does not mean you cant try it out

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