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(Con)fusing Victron Lynx/shunt system main fuse redundancy with server rack batteries + switches necessary?

Jasonm54

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Aug 17, 2022
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6
Hi all! First post...



Is it really necessary to add a battery disconnect switch and a "T class" fuse in-between a Victron Lynx setup (with a properly sized + Victron recommended main fuse) and a server rack battery (with bms and breaker switch)?



Setup in question:



X2 24v EG4 server rack batteries with integrated 125amp breaker on/off switches - specsheet/manual state various bms overcurrent safeties and breaker capabilities



Victron Lynx shunt with recommended 300amp "main fuse" and Lynx distribution block. (Also assume overkill wiring sizing and extremely short lengths)



Multiplus II 3000kva 24v 120v x2 inverter



I would like to keep the system as simple as possible. Less connections are better right?

I understand the concern for arc extinguishing high current T class fuses vs what Victron recommends but under what failure circumstances are we trying to prepare for?
 
Ok so let me see if I got this straight.

2x EG4 batteries with built in over-current protection and means of disconnect
2x multiplus 2s that have an modal switch to turn them off(means of disconnect)
1x lynx shunt
1x lynx distributor

A lynx shunt only makes sense between 2 other lynx components.
A victron smart shunt is under half the price of a lynx shunt and would do what is required.
Multiplus 2s are optimized for use in RVs, is this a mobile application?

The class t fuses are useful if you don't trust the batteries breaker but the overall topology is puzzling.
 
Ok so let me see if I got this straight.

2x batteries
2x multiplus 2s
1x lynx shunt
1x lynx distributor

A lynx shunt only makes sense between 2 other lynx components.
A victron smart shunt is under half the price of a lynx shunt and would do what is required.
Multiplus 2s are optimized for use in RVs, is this a mobile application?
Only one Multiplus 24v inverter (120x2 model for a 50 amp RV )

Two 24v EG4 server batteries in parallel

X1 Victron Lynx shunt and distribution block
 
Only one Multiplus 24v inverter (120x2 model for a 50 amp RV )

Two 24v EG4 server batteries in parallel

X1 Victron Lynx shunt and distribution block
There is a lynx distributor and a lynx power-in
The power-in is un-fused
The distributor supports fuses.
Did you already purchase this hardware?
 
Everything is on paper right now.

I thought the lynx shunt with main fuse and battery temp sensor features would be a clean way to tie into the distribution block? Can the battery bank not tie directly into the shunt?

I'm thinking about future expansion of 3 24v server batteries. The Lynx power in block could be added for a common bus bar input for the battery bank.
 
Everything is on paper right now.

I thought the lynx shunt with main fuse and battery temp sensor features would be a clean way to tie into the distribution block? Can the battery bank not tie directly into the shunt?
Are you referring to the distributor or the power-in?
 
My system would be: server battery > Lynx smart shunt > Lynx distributor

(Lynx power-in could be added later on for expansion)
 
Here is what I would do instead.

get a lynx power-in https://www.victronenergy.com/dc-distribution-systems/lynx-power-in
and a smart shunt https://www.victronenergy.com/battery-monitors/smart-battery-shunt
Attach each battery to an un-fused branch position on the power-in
The attach the inverter/charger to a fused branch position
Use this video to make the inverter/charger branch fused
connect the shunt on the negative inverter lead between the inverter and the lynx power-in

You will have 1 free branch position and the backplane will be free on either side for future expansion.
smart shunts are probably easy to sell on if you want to upgrade to the lynx shunt when/if you expand beyond the capabilities of the power-in.

Saves you some cash and prevents daisy chaining your batteries.
This video will explain one of the reasons why its a bad idea to daisy chain your batteries.
There are others.
If you are curious I can explain.
 
Oh and if you don't trust the battery breakers add a class -t fuse as close to the battery positive terminal as possible.
 
Here is what I would do instead.

get a lynx power-in https://www.victronenergy.com/dc-distribution-systems/lynx-power-in
and a smart shunt https://www.victronenergy.com/battery-monitors/smart-battery-shunt
Attach each battery to an un-fused branch position on the power-in
The attach the inverter/charger to a fused branch position
Use this video to make the inverter/charger branch fused
connect the shunt on the negative inverter lead between the inverter and the lynx power-in

You will have 1 free branch position and the backplane will be free on either side for future expansion.
smart shunts are probably easy to sell on if you want to upgrade to the lynx shunt when/if you expand beyond the capabilities of the power-in.

Saves you some cash and prevents daisy chaining your batteries.
This video will explain one of the reasons why its a bad idea to daisy chain your batteries.
There are others.
If you are curious I can explain.
something like this:
1660788264706.jpeg
But follow the instructions above and change the connections from the inverter to the shunt and the disconnect switch.
 
Thanks for everyone's input. I'm going to sleep on it and rethink my plans . ?

I watched a few more videos on YouTube.

I thought that possibly two batteries daisy chained would not be the same issue as 3+ batteries.

Using the lynx power In module + cheaper smart shunt looks like a "smart" idea (in conjunction with the pwr in mods)
 
Sorry to revive this thread, but I am inline with @Jasonm54's initial idea to use a Lynx shunt followed by a distributor.
Is the only reason not to do this cost? I'm not distilling any other logic here, but want to be sure I'm not missing anything.

To me it seems the cleanest to do the shunt into the distributor. Thoughts?
Thanks!
 
Context: Two of my LFP batteries (48v/202AH each) do not have CB's built in.

I am using a PowerIn as a busbar to parallel my batteries but they each have a Outback 125aDC CB before the PowerIn acting as protection and as a on/off power switch.
I will be adding two SOK's to the other two positions on the 1st PowerIn.
Then there is a Lynx Shunt with 300a fuse as recommended. The Lynx shunt will be connected to my Victron Color Control.
Then another PowerIn to connect my 2 Quattro inverters and 2 Victron 150/70 MPPTs. All four will be fused inside the 2nd PowerIn.

I can turn off the battery power to the shunt with the CB's all located before the 1st PowerIn.

Based on all of this I thought it reasonable that I could not use a Class-T fuse between the 2nd PowerIn and the inverters. Does anyone disagree?

Note: The reason I am not going with a Lynx Distributor vs the 2nd PowerIn is no need for the indicator lights which saves me money.

Sample1.jpg
 
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