dc system Image

dc system

Negative DC Loads while charging, positive while discharging (increases with load)

Before I start I want to say I've read through quite a few posts already where folks are describing negative DC loads, however I have not found anything that quite explains what's going on.

Some background on my setup: I live off-grid and run my home off our solar/battery setup. I recently switched over to a new 48V battery system I build, we have all new hardware, Multiplus II 48V, two victron charge controllers, smartshut...etc.

I see negative load on the DC side (indicating a charge coming from DC). This is odd as other than our charge controllers we have no other DC charging sources. However if we have a large AC draw (3Kw when running our well pump) DC load spikes to around 100-200W.

I'm perplexed because I never saw this on our previous system. What could be going on? Below is a schematic of our system:


During the evening (no solar input):


During the day (solar input/net positive load to battery)


I am using my own graphing system but my Venus device displays the same data as well.

hummingbear asked
hummingbear commented ·

2 Answers

SmartSolar MPPT 75/15 Load Output Settings

I will be utilizing the load output on my SmartSolar MPPT 75/15s (3 of them for different arrays). All my loads will be 12v DC. Do I just set the output at 12v or do I need to calculate for voltage drop through the bus/wire?

adrianp105 asked
adrianp105 commented ·

1 Answer

DC loads/DC system in ESS


I have a 3-phase system 3x5kVA MPII, 1xMPPT, 2xFronius Symo, BMZ lion battery 48V with BMS, everything is controlled by Cerbo + ESS assistant. Everything has current FW, AC Coupled feed in excess - ON, DC Coupled feed in excess - OFF. Now I canceled home UPS APC (for home server, CCTV...) installed Phoenix inverter and SmartShunt. I turned it on in Settings - System - Has DC system ON. I set the SmartShunt as DC Loads. Unfortunately, I have two problems.

The first problem - the DC loads field does not appear on the display. It only appears immediately after a restart, or on the display that I'm not using.

Normal view ( No icon DC Power displayed ):


Display after restart Cerbo: (as soon as ESS assistant starts, the DC loads field disappears)


Another screen I don't use, here is the DC loas to see:


Would it be possible to modify the FW to show the DC load on the "primary" screen like here?


The second problem - if the battery is charged, CCL 0A. When I turn on the DC load, the battery discharges and micro-cycles (100% -> 97% -> 100%...). Unfortunately, the MPPT does not supply any power (to balance the draw from the battery), the Symo supplies power to the grid. Is this normal behavior? Shouldn't the MMPT regulator supply the same power as the Phoenix draws so that the battery is not constantly being discharged and charged? It can be seen in the pictures above.

Thank you for the responses, or for the advice.


ondra asked
janr-1 answered ·

1 Answer

keine Kompensation des CCL durch DC Last


noch neu im Zusammenhang mit Victron Komponenten habe ich eine Frage zur Kompensation des CCL, wenn eine DC Last angeschlossen ist. Meine Konfiguration besteht derzeit nur aus einem MPPT BlueSolar 150/35 und einem Smartshunt 500A/50mA, der direkt am Ausgang einer DIY 8S Batterie mit 280Ah Zellen und JK-BMS angeschlossen ist. Das BMS ist über RS485 -> USB an ein Venus OS auf einem RasPi angeschlossen. MPPT und Smartshunt per Victron Ve.Direct/USB Kabel gehen ebenfalls zum RasPi. Da ich (noch) keinen Multiplus II besitze verwende ich einen Soyo Inverter mit Nulleinspeiseregelung, der seine Energie von den Busbars der Batterie/MPPT erhält,zur Wechselstromerzeugung.

Es funktioniert auch alles soweit ganz gut mit der externen Steuerung des MPPT mit der Anpassung des Ladestroms durch das BMS je nach Ladezustand (SOC) der Batterie. Jedoch wird nicht, wie im Victron Handbuch beschrieben, der Ladestrom (CCL) in Abhängigkeit von der DC Last ( Soyo Inverter), nach oben angepasst. Es heißt aber auch bei Victron, dass der Shunt als Gleichstromzähler konfiguriert sein sollte. Da sowohl die Vewendung als Batteriewächter oder Gleichstromzähler keine sichtlichen Veränderungen, insbesondere was die lastabhängige Kompensation des Ladestroms anbelangt, ergab, habe ich den Smartshunt direkt in den DC Lastkreis gesetzt, aber auch dies führte nicht zum gewünschten Ergebnis.

In der Praxis führt dies dazu, dass trotz genügend vorhandener Solarleistung, der MPPT soweit herunter geregelt wird, dass zu wenig beim Inverter ankommt und sogar Energie aus der Batterie entnommen wird.

Meine Fragen sind nun

1 habe ich etwas falsch konfiguriert

2 ist mein Vorhaben überhaupt mit den vorhandenen Geräten realisierbar

3 ist evt ein Multiplus erforderlich

Aus meiner Überlegung würde ich sowie einen Multiplus als ESS mit Nulleinspeisung verwenden, habe aber derzeit beim Netzbetreiber nur ein „Balkonkraftwerk“ angemeldet und scheue mich vor dem Schritfverkehr und evt Vorgabrn/Einschränkungen.

Vielleicht kann mir jemand von Euch weiterhelfen mit einer Lösung.

Danke und viele Grüße


hdschardt asked
hdschardt answered ·

2 Answers

MPPT Output Under Load

I've noticed that many times when it's nice and sunny and the batteries are fully charged if I turn on a heavy load the 100/30 MPPT won't provide any current from the solar panel until the batteries are significantly discharged, sometimes not even then. Sometimes it will only start providing current the next day. Why doesn't the MPPT always respond to load on the system by outputing current form the solar panel?

robert-barnesi asked
mihaitaiosub edited ·

2 Answers

Phoenix 12/50 Missing in the manual...

Hey there,

I'm new to being a boat owner and therefore to the charger I bought with that boat. It's a good charger i hear because it's a Victron energy charger. Now the thing is, I am not a complete novice when it comes to electricity and so I noticed whoever did the electrical system in my boat, did not do a very meticulous job. I am going to do a better job.
So I read the manual of my charger and I am left with a few questions. Some because I've not been working with DC very much. I cannot find the answers in the manual at this moment.

1. The trickle charge to starter battery is not being used at the moment. There is not much information on the trickle charge circuit in the manual. What type of cable is advised over a two meter distance?
2. I assume, but I don't like that because assumption is known to be the mother of let's say, very big mistakes, the trickle charge circuit is also controlled by the microprocessor and will be able to keep the starter battery charged over a long period of time without overcharging it. Is that correct?
3. The manual says the full charging current is 'divided in two main outputs'. Does that mean I can use both outputs on one battery, as I have only one? I don't seem to be able to remove an output cable without breaking the factory standard.
4. At this moment the 'voltage sense' circuit is not connected, yet the charger moves from bulk, to absorption, to float. Is there any good reason, and I assume there is, to finally start using that circuitry?
5. The temperature sense circuit is not in use. The manual says a sensor comes with every charger. Yet I find no sensor. Looking at the connection diagram, I assume the mentioned sensor is on the board. So just to be sure, is there a separate device that is the temperature sensor? And what type of cable should I use?

Many thanks to anyone who can help me improve the electricity on my new classic second hand boat.

Thomas Tchong asked
klim8skeptic answered ·

1 Answer

Will the Fuse LEDs on Lynx Distributor illuminate without the 4-pin cable supplied with unit?

Trying to use the Lynx Distributor (and Power In) without the Lynx Ion Shunt or BMS (using BYD batteries). I had assumed the Fuse LEDs would illuminate with a working fuse in place and powered, however a line on the old Victron Live page for DC Distribution Systems suggests that this small data cable is used to power the LEDs (rather than taking power from the busbar itself). I cannot get the LEDs to illuminate - are the LEDs useless unless using the Lynx Shunt? Because Lynx Shunt uses CANbus, it cannot be used in conjunction with BYD on a CCGX (though I think VGX would support it).

midsummerenergy asked
rikhf edited ·

7 Answers

Strange DC Power Values

Hi All

New yacht install - all new kit. In process of commissioning.

System -> 4x 330Ah Start Lithium, connect in parallel to Lynx Distributor, connected to Lynx Smart BMS, connected to Distributor on other side. Cerbo GX and Touch 70. No loads, no charging devices attached the the final distributor.

This is what the GX Touch is showing - and it looks normal.


This looks as I would expect to see, battery showing -0.4A and -5W and the DC Power showing 5W - which is about right for the consumption of the BMS, Cerbo and Touch 70. So... all good so far.

I have then attached a Victron Smart Charger 5A - to the distributor on right of BMS - to slowly charge the batteries, very slowly for the first time and balance them.

I see this...


Prefect - the DC Power is now showing -59W as power is going in to batteries.

Next - I have disconnect the small 5A charger and have attached the new Multiplus II for the first time, Connected to the distributor on the right of the BMS. Connected VE.Bus and +ve and -ve DC wires only. No AC connections made at all. Not connected to mains AC and no AC loads connected.

When doing this I would expect to see the DC power be shown as a load. I would expect it to be about 5W for BMS, Cerbo and Touch.

This is where it gets strange....


DC power has changed to a -VE number - suggesting is is being charged with 6W. The AC loads look normal - 16W for the Multiplus - inverting - but idle.

Can anyone suggest / explain what is happening here ?

Kind regards, Tim

miya asked
miya commented ·

2 Answers

Überspannungsschutz - Strings zusammenlegen?

Hallo zusammen, vielleicht gibt es hier jemanden der mir weiter helfen kann. Anlage sind 5 Strings a 2 Module. MPPT 150/85 und Multiplus2 5000 sind verbaut. Ich fände es sehr aufwändig jeden String separat mittels Überspannungsschutz zu bestücken. Meine Idee, nach der Sammelschiene PV und vor dem MPPT, gesammelt mit allen String in einen Überspannungsschutz Kasten zu gehen. Wie sieht es denn bei euch Victron Mitstreitern Zuhause aus die mehrere Strings haben? Mit besten Grüßen Felix

fx90 asked
fx90 edited ·

0 Answers

Looking to add 3 lithium batteries to my lead acid system. One or two dc-dc chargers?

Hello I currently have a set of lead acids charged by solar panels. Im trying to add in a set of lithiums to the array. Does anyone know if dc-dc chargers only work one way? Or perhaps I need two? The idea is to have two different chemistries and be able to charge and use them at the same time without needing to switch manually.

burgboy asked
kevgermany answered ·

2 Answers

GX Touch 50 shutsdown/reboots when switching on/off a certain breaker

Hi all, i have a GX Touch 50 hooked up to a cerbo. The Cerb power leads are connected to the primary DC service switch - connected to the side from the batteries so the switch does NOT interrupt the power to the Cerbo.

It isn't 100% of the time, but it happens maybe 20-30% of the time when i switch the breaker on my DC panel for my USB outlets(the most common switch i switch on/off), my Touch 50 will shut down and reboot. I dont believe the cerbo is actually shutting down but being it is in a different location, i can't fully confirm this but i dont seem to get disconnected when connected via bluetooth. I"ve gone through all the connections and everything is tight as should be.

Anyone have an idea on whats going on? Just an annoying thing thats occurring at least 1-3 times a day

jordan-de-geus asked
gary-3 answered ·

3 Answers

Wiring help Truck with 48v system Questions

1. What fuses or breakers do i need and where?

2. Is the wiring right or does something need to be moved or added?

3. Shunts, Cerbo GX, etc needed?

4. Lynx 1000 needed?

5. This will be completely off grid

6. Is MPPT needed for EasySolar 2 GX?

7. Winch straight to battery or connected to paralleled Orion-Tr’s?


Updated down below



lpez210 asked
lpez210 edited ·

4 Answers

Metering Overall DC Loads (and Excluding Sources) When System Includes a Third Party Inverter/Charger?

Disclaimer: While I am somewhat experienced in the area of off-grid electrical systems, I have yet to have any hands-on experience with Victron's products, so the following question comes from the perspective of someone who has only been able to read the datasheets and manuals.


A friend of mine is tired of having to run the noisy fuel-guzzling generator every day to recharge the battery bank on his 49 ft sailboat. Instead of incrementally installing random PV panels until the problem goes away, he wants to first install equipment for recording his DC usage this cruising season so that he can determine his real-world requirements and design a system that balances the desire for extra capacity against seaworthiness concerns and aesthetic considerations.

The plan is to meter the loads downstream of any charging equipment, so as to not have the data obscured when the "service"/"house" battery bank is being charged, such as when motor-sailing or running the generator. For typical DC loads, this is fairly straightforward, and Victron's SmartShunt product in "DC energy meter" mode looks like a good option. If combined with one of Victron's "GX" products, I gather there is even the option of taking the sum of the values from multiple SmartShunts in "DC System" mode, which would be convenient if my friend later decides that he wants to get collect data on individual system branches while still seeing/recording his overall energy use.

The main complicating factor is his third party inverter/charger, which can either be a DC load or a DC source, depending on whether or not he's got the generator running (or is connected to shore power). Short of replacing the inverter/charger with discrete devices, I can think of a few approaches to this issue, some of which are better than others, but none of which seem ideal:

  • We could install a single SmartShunt downstream of the inverter/charger, but then we'll fail to account for all of the DC that goes into supporting AC devices via the inverter.

  • We could install parallel SmarShunts (one for the inverter/charger and one for everything else), but then I would imagine our "DC System" readings in the GX software will be thrown off whenever the inverter/charger is in charging mode.
    • A less-than-complete workaround here would be to suppress/zero-out the readings from the inverter/charger's SmartShunt whenever the inverter/charger is acting as a source. Is there a way to do this in the GX software? If not, has anyone achieved this by using a high-current relay/contactor to bypass the SmartShunt and short the inverter/charger's DC- connection directly to the upstream DC- bus? (I'm imagining an AC relay/contactor that is activated whenever generator/shorepower is live.)

    • I have characterized the workaround discussed in the previous sub-point as less-than-complete because it fails to allow us to take into account for what the DC inverter's consumption would have hypothetically been if generator had never been switched on. Does anyone have a solution here? Does Victron have a standalone GX-compatible AC current sensor that we could use to record the load on the third-party inverter/charger's AC output at times when it is in AC bypass mode due to generator/shorepower (and only at those times)? The idea would be to convert use the data for these periods into estimations of what our inverter/charger's DC use would have been had the generator/shorepower not been online, taking into account the inverter's conversion loss.

Thanks in advance for any solutions!

aaron508 asked

0 Answers

Multiplus 12/3000/120 not inverting on battery power

Have scoured the forums but no solution found. I am in the process of mocking up the system for my camper and for a week or so, the Multiplus operated just fine. However a few days ago, nothing works when on DC. No inverter, no unit power on when connected to a fully charged (13.37V) battery via 4/0 cables and voltage checked at the studs on the Multiplus.

When connected to shore power, normal startup works fine, after a few moments the mains LED lights up and battery charging working fine.

Checked everything, started clean by updating the firmware via Victron Connect (current firmware is v494). Still no lights...nothing when AC is removed and cannot connect via VC when Multiplus is solely on DC power. There are no modifications in configuration other than selecting Lithium batteries, and yes the battery voltage for inverter shutdown is set at 11.4V. I am at a loss, all assistance greatly appreciated.

john-gibson asked
john-gibson answered ·

7 Answers

Use smartsolar as a dc dc converter

Hi there

Here's the situation : I have an electric vehicle with 72v batteries inside. What would happen if I disconnect my solar panels from the 250 / 60 smartsolar and plug the 72v instead ?! I guess it's gonna work like a dc dc step down charger with my 56.8v lifepo4 battery !!!???!!!

And what would happen if this 72vdc battery is plugged IN PARRALLEL with 220vdc solar panels (6 trina vertex 400 in series) to the smartsolar's PV input ?

Even weirder : the fact is that my 72vdc vehicle can be directly charged by a 54vdc voltage. So how fried am I if I have PV + 72v battery on the smartsolar pv input... + my EV controller (not directly the 72v battery, this controller charges through the motor used as an induction) on the smartsolar's 48v battery output ?!?!?!?

Of course I see some diodes, fuses etc potentially added but let's discuss the questions above first, please.

I imagine a situation in winter when I don't move from home and would be happy to reduce daily manipulations on the system. The other huge advantage would be that my vehicle can be used to charge 10kWh outside of my offgrid facility and come back to feed my system in case of super bad weather. Big battery on wheels !

csc asked
Alexandra commented ·

9 Answers


124 Posts
119 Users
1 Follower

Topic Experts

175 Points
9 Points
0 Points