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system design

Multiplus 12/1200VA Relay output usage for cooling fan?


Im planning on installing a Multiplus 12/1200VA inside a steel enclosure with a lithium battery.

The enclosure will be outdoor wall mounted and will receive sunlight in the afternoon. Im going to be adding a cooling fan to keep temperatures inside the case down. So ive read you can set the alarm relay to turn on when the multiplus internal fan turns on.

First question, what is the current rating for the relay? I cant seem to find a current rating for the relay anywhere? Id like to fit quite a large fan.

Second question, at what temperature does the internal multiplus fan come on? I want to avoid a situation where the multiplus is under no load so it doesn't deem it necessary to tun on its fan while the ambient temperature in the enclosure is lets say for arguments sake 60 degrees celcuis and busy cooking my lithium battery.

Third question, im going to have the external temp sensor of the multiplus mounted on the battery obviously. Would i be able to control the alarm relay using the battery temp reading?

ferdie asked
Alexandra commented ·

3 Answers

Help with battery switchs for motorhome?

I am in the process of designing the system for my motorhome looking for help to configure the system disconnects. The main components:

  • 4- 440W solar panels > 4 DC breakers/disconnects > 4 MPPT 100|30 > Lynx Power In
  • 8- 100Ah Lion UT-1300 > 2 - Lynx Power In
  • MultiPlus II 12 | 3000 | 120 2x120
  • Orion-Tr Smart DC-DC Charger Non-Isolated 12 | 12 | 30

I plan on a Battery switch on the starter battery negative terminal.

The coach system, I am planning to use a Shallco Bi-Stable Latching Relay BR-300-12-1-34 on the main negative terminal of the Lynx Power In before the Smart Shunt.

This should provide 100% battery disconnect from system. At this point the MPPT should turn off.

My question is: with the motorhome being all electric (no propane) is there any need for additional battery switches on the 12V input to MultiPlus II and/or the Solar output from the Lynx Power In?

This is my preliminary diagram


Glen Carter asked
kevgermany commented ·

4 Answers

series-para wired or other?

I have 3 mismatched panels where voltage is 1500v vs 7 x JA panels 1000v, amps voc etc are similar. The 10 panels are all on a platform without shading all south facing lenghwise at 15 deg elevation. At the moment Marekp correctly identified the layout but now no shading but 3 different panels i am wondering if they should remain in series 5 x 2 or is it benficial to put in 3 odd ones in para string of 3 and 7 as a string in series. Currently the easysolar gx II 48v 3k/250/70 (35) is wired before the inverter with 32a/200v and an spd but wonder if too low on voltage have inline 15a/1000 om each string on the Ja 380/logi 370 and a shokkty diode on both too, Y connectors to 2 poles - pylontech x 2 / 3000 and 40a AC connection for mains unit


Andrew asked
Jons Collasius answered ·

1 Answer

3.8kw Offgrid: Victron EasySolar 2 48v.35 with mppt 250/70 3000w Design + Fuses

Is the below correct before I go further? Thanks in-advance

PV 3.8kw Offgrid: Victron EasySolar 2 48v.35 with mppt 250/70 3000w

  1. Panels = 10 x JA SOLAR JM60S20 380/MR 380W VOC 41.62 V VMP 34.77 V ISC 11.47 A MP 10.93 A CLASS II MAX SYS 1000V, MAX AMP 20 TOTAL 3,8KW

  2. two strings 5 x 2 in series and wired series parallel, only one mppt and costly for another so all panels same direction height etc.PV Wiring = 6mm x 10m to inverter from shortest end 17m from last panel. 2 shocty diodes inline on each string + 1000v/20a to prevent reverse polarity. Then 32a 1000v disconnect before going to inverter

  3. Storage Pylontech 3000 and 3000c with 2m pylontech victron cables of correct size with 2 x 120a fuses on each pole.

  4. AC As this is not mains connected I am wondering what sort of consumer unit as have a few given to me but only need one ring main - .2 at the most for garden tools, But note easysolar has 2 ac outputs, does this mean no consumer unit is needed?

Does this configuration sound ok?

Andrew asked
Andrew edited ·

3 Answers

Lithium SuperPack drop-in replacement feasibility

Hi, I've been reading though all the posted questions but can't find a clear answer.

I'm considering replacing the current AGM house bank on my boat with SuperPack batteries, and I'm trying to understand what it would involve.

Below an attempt to visualize my current setup:


I understand that I'll have to replace the shore charger for a Lithium one, but beyond that, is there anything else I would have to replace/modify, or will the SmartPacks be a simple "drop-in" replacement?

My main doubt is:

Since the BMS is integrated, what will happen if the batteries are fully charged and the engine/alternator is running? Is there a risk the BMS will trigger the over-charge protection and disconnect all the loads (e.g. loosing plotter and instruments when approaching an anchorage/marina)

Any other suggestion/input is highly appreciated, like: does the Argo Fet still make sense with the SuperPack, or should I replace it with an Orion-Tr DC-DC charger? Do I need a separate external BMS to protect the batteries from overcharging?

Thank you!

badrock asked
badrock answered ·

3 Answers

System design. In Buckinghamshire

Hi everyone

im struggling with system design and what I need. ideally I would like everything to run off of backup batteries as well But my system is split already.

So I have a Henley block from the main income splits the garage consumer unit and the Houses consumer unit. I have a 3.3kW array, solis ac coupled inverter to the houses consumer unit. The Batteries and Victron Inverter would be installed in the Garage.

ideally I would like the solar, loft kitchen and the garage sockets to operate in a grid down manner still ie so I would have to split out the house consumer unit or run the mains to the garage and take it back to the house from the inverter but also have provisions to switch back to grid in the event of inverter replacement.

I looked at the 48/8000 Multiplus which is capable of 100Amp switch so would run the house without overloading, the 48/5000 is another option but would see me having another consumer unit in the garage and another in the house inorder to split the garage sockets , and in the house the loft, kitchen and solar.

I am aware I’ll need to run SWA cable depending on the options of inverter. I’m capable of running two 25mm SWA cables to satisfy 100Amp draw. I could run Cat5e Cable to the garage for the ESS but I have no idea how many pairs I would need to run to the cerbo GX so that I could monitor the solar as well as the incoming from the grid. Also how many Pylontec batteries would I need for each Multiplus 2?

Any help with design would be appreciated and PS is there Victon installers in Buckinghamshire?

daza asked
daza edited ·

16 Answers

Help Expanding motorhome off grid system

Hi, I can't find any posts that I can understand sorry. So hopefully someone can guide me in this journey.

Currently We live in a 12 metre bus totally off grid for probably 90% of the time. We have been traveling permanently for 7 yrs.

My set up right now, is as follows.

6 x 260W 20V 60 cell solar panels wired in pairs, series & parallel at the DC RCD box.

Victron multiplus 12/3000/120-50

Blue Solar MPPT 150/85


3 x 340ah LiFePo4 batteries in parallel to give me 1020AH

I used to have AGM batteries with slightly less total AH.

I have found that the LiFePo4 batteries seem to take a lot longer to reach 100% than the AGM's did.

I also am changing to an induction cooktop and electric instant water heating. These will require a larger current demand.

My questions are

1) Do I need to get a 2nd MPPT and/or inverter?

2) if above is yes, do they need to b Victron or could they be another brand like Epever maybe.

3) What size of above would I need, do they have to be exactly the same.

4) Obviously I need to increase the total power demand capability, but I am not sure how.

5) I have enough roof space for another 4 panels only.

I think that's about it. I would greatly appreciate any assistance to help me move forward.

Cheers Doug

doug70 asked
doug70 answered ·

4 Answers

Help running a farm almost off grid

With climate change and the recent 400% electricity price surge in France my farm is on standby. I need a lot of power to irrigate and to run some basic equipment. At this moment, (unless it rains) I am contemplating a lost year, working for nothing and it is not sustainable. I do not have many options, I am thinking solar with batteries and only use the grid at night to recharge batteries. I have been educating myself on Victron energy systems and would like to have your advices on the system I need to design.

I am Triphase, I use 3500 kW/h a month in summer and a bit less in winter, heat is provided by biomass. The most power I need is 22 kVA once in a while in the summer (irrigation mostly at night.) In winter power is distributed more evenly because of indoor activities and biomass heating.

I have room for 100 solar panels and space for a nice technical and battery room. Right now I pay 1 euro kW/h peak, 60 cents normal, 25 cents at night and maybe half that in the next summer.

This recent price increase has shattered my trust in the French electricity system and I believe that it will no longer be run as a public service and more like a high-margin business. The era of cheap electricity is over for a while.

Any comment or ideas?

Best regards,


schopp asked
Michelle Konzack commented ·

4 Answers

Considering 24V System But...

I am currently planning a system upgrade of my 2022 Valor 37v13 from basic solar to a complete system that can run all loads (120V and 12V). Considering going 24V on the DIY batteries but I am struggling to elegantly solve for high current 12V loads: balancer jack pump slide motors, and genny start. Jack pump states 50-100A fuse and the gen is typically 300 CA.

Any recommendations or experience?

heckler40 asked
derrick thomas answered ·

3 Answers

2 core 12v cable - temp rating and insulation

Hi everyone - I’m currently making purchases for my system and a buying cable (2 core 1.5mm for all the 12v work). What seemed like a simple task gas given me a bit of option paralysis that I was hoping for some help with. I’ve read that I need arctic rated cables but these cables are extremely thick such as this (9mm outside diameter which seems excessive for 12v). I then also see sites run by electrics experts who are selling very stock standard 2 core as their 12v option. I’m also confused because the auto electrics in the van aren’t this protected. I’m the UK where it doesn’t get that cold or hold (-10 Celsius is about as cold as it gets and very rarely).

any advice appreciated, thanks for reading

Dylan Tucker asked
kevgermany answered ·

3 Answers

Catamaran Victron Design Feedback

I have put together my first draft layout of Victron devices and would appreciate some feedback on whether it looks correct. I have only included the positive connections and the device models (amps, etc.) have not been decided on yet.

My main priority is to keep both the house and start battery banks charged without any chance of the house draining the starter batteries. I want it to be suitable for the current house AGM batteries and also for the future house Lithium LiFePO4 with just a battery swap out and reprogramming of existing devices.

Any ideas or feedback would be much appreciated.



uniopp asked
JohnC commented ·

4 Answers

Another way to prioritise solar.

Since I installed my system I've been looking at ways to prioritise solar over grid without using ESS.

Currently I have programmed my Multiplus with an assistant to ignore ac input if aux input is open circuit and do not ignore ac input if aux is closed.

Then I use my bmv to set it's relay on (allow ac in) if SOC <50% and set it off again when SOC >99%. this is my summer setting. this is a common way to prioritise solar and is suggested by Victron.

I also have an over-ride switch in parallel with the bmv relay for winter which allows ac in all the time and prevents un-necessary cycling of the battery when there's not enough sun.

I'm about to fit another mppt controller (150/45) and have noticed that this particular controller has it's own programmable relay (not all 150/45's have this and some other 150 and 250 versions have it) which can be programmed to operate during daylight.

my plan is to wire this to the multiplus aux input via a three way switch so I have a choice of summer-use bmv relay, winter-do not ignore ac input, and spring/autumn-use mppt to ignore ac input during the day but allow it at night.

note that the normally closed contacts of the mppt relay should be used as they will be open during the day.

I hope this helps others trying to prioritise solar. :-)

bigbadbob76 asked

0 Answers

VE_Bus charge power. System balance.

Warum ist Quellen - Senken = VE_Bus charge power? Wohin fließt diese Leistung?

Why is the Sources - Sinks = VE Bus charge power. Where is this power flowing?


System Scheme (screenshot from a different time):


shubham asked

0 Answers

Solar along with the grid to supply AC loads


Is it possible that PV can run the AC loads or at least contribute to the grid supply. Today for example, plenty of sunshine and a full battery. the PV chargers only letting through 5w, while its taken average 200w to run the AC loads. An ideal scenario would possibly be. Solar tops off the batteries first thing in the morning, then between solar and battery storage the AC is run for the day, Only using the grid in the evening's to help with the short fall of power. Is this looking for to much from the system ? We are using two MPPT, 250/100, 150/35 along with two multis.Screenshot_20230118_140414_Chrome.jpg

tighernan asked
tighernan answered ·

2 Answers

How to connect two Island Log-cabins via 230Vac?

I have a Log-cabin in the Alps with 2x SmartSolar MPPT 250/100 VE.Can, CCGX, 1x Victron MultiPlus-II 48/5000, 48Vdc 9kW Batterie, 4.2kWp PV Array.

Now my Neighbor (70m Cable-Distance) would like to link in.

The Idea is to bild a separat Island System a the Neighbors Log-Cabin and link both Island-Systems via 230Vac.

Should we link both Inverters via VE.Can over the 70m distance or does there exist a solution to just use the AC-Line?

Pascal Maag asked

0 Answers


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