question

Matt Knight avatar image

DC Charger

I originally posted this on the victron-dev-venus Google group, but wanted to move it over to here as this may be a more appropriate place for it now. Here's a link to the original post:


https://groups.google.com/forum/#!topic/victron-dev-venus/_PTx0MxDNG8


Basically, I have a REDARC BCDC1240D DC-DC charger that I use to take power from the truck alternator and charge the LiFePO4 batteries in the trailer. If you're interested in reading more, I wrote it up here:


https://www.adventurousway.com/rv-electrical-upgrade-part-3-dc-charger-truck-12v-socket


It all works well, except because the DC-DC charger isn't Victron (and Victron don't have a suitable product), it doesn't talk to the Victron system - i.e. the CCGX. This means that all the CCGX displays is a net DC figure - but I have no way of breaking that down into how much energy is coming in from the charger (e.g. PV) vs how many energy is being consumed by DC loads in the RV.


In fact, from a data perspective, the device is dumb - there's no way data / comms available from it at all. My plan is to build a small MCU-based device with an INA3221 (essentially three INA219 chips combined) to measure the current and voltage on the 3 legs of the charger - PV input, alternator input, charger output.


My question is about the best way to get this data into the Victron system. My thinking was simply to write on the relevant MQQT topics so the charger shows up as a new device. Will that work? Has anyone done this before, and specifically, Victron doesn't have an appropriate device type for a DC-DC charger so I'll have to create some topics of my own.

CCGX Color ControlVenus OSMQTT
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2 Answers
Matt Knight avatar image
Matt Knight answered ·

@markus Haha, no worries! I will soon be installing a Victron solar charge controller for some roof-mounted panels, but we use the REDARC DC-DC charger for pushing 40A of charging current from the truck to the trailer. As an added bonus, the REDARC charger has an integrated MPPT charger so we use that for a small, portable solar panel. Although it's not often we have both alternator and solar panel inputs active (we can't really drive with a portable panel attached!), we do sometimes use the truck as an "emergency generator" when we're parked somewhere for several days and need more juice!

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:o) I have my portable panel mounted with good suction cups, additionally secured by a belt through the carrying handle. It didn't came off so far and my 4x4 is raised enough, so the cops can't see...

Markus avatar image
Markus answered ·

Hi Matt,

I think the simple way would be, to add another shunt to the system to measure the current, coming from the DC Charger.

If you add another BMV, you could see this current in the device list of the CCGX.

If you know a bit programming, modifying systemcalc.py and or GUI .qml files can be a way to show the data from 2nd BMV on the tile screen of Venus.

Editing files in Venus is an unsupported solution tough.

Regards,

Markus

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Thanks @Markus, but I will actually be using 3 shunts to measure current and voltage on each of the 3 legs of the DC-DC charger. If I just used one on the output of the charger, I would have no way of knowing how much current is coming from the two different inputs - PV and alternator. Installing 3 BMVs would be cost-prohibitive, and I think, wasteful.


I'm more than comfortable programming, I'm just looking for some direction on the most appropriate way to tackle the problem. Is there a reason that writing to the MQTT broker wouldn't work?

Oh, i thought you were using Victron Solar chargers. I am now reading your article with interest. I didn't read it before... sorry.