question

lostandfoundadventures avatar image

Lynx distributor setup - 2 MPPTs using one fuse connection?

Hi there, very first question out here, hoping someone can help...

We are planning to use one lynx distributor (probably with a smart shunt), but are wondering if that's possible with our intended setup? - see below questions for intended setup

My questions are:

  1. can I connect the 2 MPPT controllers to the one fuse holder on the lynx distributor? if that's possible, do they need to be identical in size?
  2. can I do the same for the DC DC chargers? Connect 2 of them to the one fuse holder in the lynx distributor? If that's possible, do they need to be identical in size?


As far as I can tell we need to connect the battery (single victron 330A lithium battery) to the left-hand side of the lynx distributor. Then we would connect the following to the 4 fuse spots:

  • MPPT smart solar charge controller (for our 2 solar panels in series on the roof)
  • MPPT smart solar charge controller (for our solar blanket that we intend to setup when we are parked in the shade, but can have access to the sun a few metres from the vehicle)
  • Orion TR smart DC-DC charger - we are thinking of adding a second DC-DC charger as our car has a 150A alternator and we will drive most days a few hours and therefore will be charging the bulk hopefully with the alternator
  • IP22 blue smart charger - we will be mostly off-grid but when we park up at a friend's place we could use this to charge the batteries via shore power without having to put in a permanent connection on the outside of the car.
  • Phoenix inverter - will be used to charge our laptops at night if needed, as well as charging our headlamp batteries etc


Now, as you can see we have 5 things that I believe need to be connected to the lynx distribution module. Potentially 6 if you count the additional DC DC charger we would like to add.

I also haven't looked yet how / where the switch board we intend to add for all our 12V loads needs to be in the wiring diagram, does this need to go into a slot on the lynx distributor too? ( we won't have any 230V loads as we will plug our laptops directly into the inverter and don't have any other appliances that run on 230V)

We also intend to add a Cerbo GX with GX Touch 50. I haven't looked at how to add that to the system, but assume it doesn't need to be in the lynx distributor....



We are building a small campervan with not too much electrical needs, but we like to be able to stay off-grid for extended periods, including parking her up and going away for a week-long hike (hence the chunky battery). We are very limited in space (and weight) so would prefer not to have to add a second lynx distributor if we can avoid it :-)

(oh and sorry admins, I selected the topic 'lynx shunt' as there is nothing suitable to select as lynx or lynx distributor, don't seem to exist as a topic....)

lynx shunt
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2 Answers
Mike Dorsett avatar image
Mike Dorsett answered ·

Answer to both questions is yes you can (connect 2 sources / loads to one fuse) and no they don't (have to be the same rating).

Restrictions: The wire from the fuse to each unit should be able to handle the full current of the fuse rating. The fuse needs to be rated at 1.25 x the total current of both chargers. This applies to both positive and negative cables equally. The oversized cables will also help reduce volt drop, and hence improve the charge efficiency of the 2 chargers.

2 comments
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Hi Mike, thanks for that! I have found a schematic on the Victron website (US-VAN-Drawing-VEBus-BMS-MultiPlus-3KW-DMC-400Ah-Li-Cerbo-SBP-100A-&-65A-SmartShunt-MPPT-100-50-OrionTr.pdf) which seems to agree with you as it has 2 Orions connecting to the one fuse on the Lynx distributor. This is a section of that schematic showing the 2 orions connected together and going to the one fuse on the Lynx

2-orions.jpg

The inputs and outputs on the positive side of the Orions are protected with fuses of 60A each.

I am hoping they will one day show a similar setup for the MPPTs too, just to confirm this is an option for those of us with very limited real estate for all the electrics in our compact setups (small campervan).

2-orions.jpg (312.7 KiB)
seb71 avatar image seb71 lostandfoundadventures ·
It's not the same. You have those small busbars (and fuses) in between.
seb71 avatar image
seb71 answered ·

Don't try that.

You can stack up multiple Lynx Distributors.

Cheaper way (and not as compact) would be to make your own busbars from copper bars and use some fuse holders.

5 comments
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I’ve been pricing this out, and the Lynx bus bars are remarkably cost competitive. By the time I get two good quality bus bars of similar capacity, add in fuse holders, jumper cables, fuses, and all the other bits, I’m pretty much at the same price. Except nowI have a lot more pieces, and joints where things can go wrong.

You need fuses and wires (and "all the other bits") either way. So do not count those when comparing prices.

Also in OP's case he should count two Lynx Distributors.


By making your own busbars I mean buying copper bars and driling and cutting them yourself.


Thanks Seb71. I am aware that I can stack multiple Lynx, however, 2 Lynx take up quite a bit of space in my setup, so I was hoping to avoid that option. I am not trying to save a few dollars by not buying a second Lynx, it is more a question of space. I like the neatness of the Lynx, but don't need 8 connections (I think).... I am a real newbie to all things electrical so am still reading all the manuals and am trying not to get too confused with all the different options to try to see if I can work out the components that would work best for us :-) Victron does seem to indicate with their drawing that it is perfectly fine to link 2 Orions into the one fuse on the Lynx distributor in their schematic, so I am really hoping the MPPTs fall into the same category... Then I would only need the 4 fuses on the Lynx (1 for the DC loads, 1 for the inverter, 1 for the 2 MPPTs and 1 for the 2 Orions).... Is there a specific reason why you don't recommend it that I am missing? Thanks for your help! Much appreciated!
seb71 avatar image seb71 lostandfoundadventures ·

The purpose of fuses is to protect the wires.

This means you size wires to safely carry currents up to the point at which the fuse will blow.

On the other hand, you don't want the fuse to blow at normal current values.

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Mike Dorsett already explained this, but I will give you an example.


Let's say you have two 60A solar chargers, which you want to connect to the same fuse.


Since each solar charger is able to produce 60A (assuming you also have enough PV panels), you have a current of up to 120A into that fuse. This means you must size the fuse for 120A. So you will have to use a 150A fuse or so.


Now we are back to sizing the wires between the solar chargers and the busbar/Lynx. Each solar charger can charge with 60A, so from this condition the wire should be able to safely carry 60A.

But you have the second condition: the fuse used to protect that wire. That fuse is 150A. This means each solar charger wire must be able to safely carry 150A (otherwise, if you use a 60A rated wire, the wire will melt/catch fire before the 150A fuse blows if some fault occurs and the current goes to high values).


You size the wire based on the maximum between these two conditions, so you must size the wire to safely carry 150A. This is a very thick (and expensive) wire, which won't even fit in the solar charger terminals. And difficult to route/place in position.

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With one Lynx, you could use the free ends of the busbars to connect something (you need a fuse holder).

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Another option would be to use a small busbar and two fuse holders where you connect the solar chargers and then connect that busbar to Lynx Distributor.

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Also it is best to avoid placing more than one wire lug on a bolt. Especially for wires with high currents.

thanks so much!!! That is enormously helpful! All of it, but especially pointing out the fact that I can add another connection (if I use a fuse there too) on the free ends of the busbars. I never thought of that.... As well as the option to use a small busbar and connect that to the one position on the lynx. I will make some small changes in my diagram and think I will then be sorted with using the Lynx. Thanks so much for taking the time to respond again.