Planing to use Victron lynx 1000A Shunt but can only find fuses up to 800A

[BillCaswell]

I would think that the lynx 1000 system would require/support a 1000 Amp fuse? I can't find any 1,000 Amp CNN fuses. What am I missing from this?

 

[FilterGuy]

Wow!! how large is the system that it needs a 1000A fuse?

 

[BillCaswell]

In my sailboat, the 20hp electric bow thruster motor is driven by the house bank. It runs at 700 amp for a few seconds at a time. There is also a start up inrush current that I need to factor into my design. There may also be the 90A windlass running and other loads.

But my point is that the Victron lynx system is marketed as a 1,000 amp system. How can this be if the biggest fuse that I can find is only rated at 800 amps?

 

[John Frum]

@BillCaswell please ask Victron and report back.
I await the answer with keen curiosity.

 

[BillCaswell]

Not the best answer...

 

[John Frum]

No the best answer...

View attachment 131313

What exactly was your question to Victron?

 

[BillCaswell]

Check the initial posting in this thread.

 

[FilterGuy]

It is common for a busbar to have a total rating that is different than the per-connection rating.

With a 4-lug 1000A busbar, you can not have 1000A going in on two of the lugs and 1000A going out of two of the lugs, but you could have 500A going into two lugs and 500A coming out of two lugs.

 

[John Frum]

Check the initial posting in this thread.

You asked two questions in the original post, is that exactly what you sent to Victron?

 

[BillCaswell]

You asked two questions in the original post, is that exactly what you sent to Victron?

verbatim

 

[John Frum]

verbatim

Charitable interpretation is they misunderstood the question.
Less charitable interpretation is they pretended to misunderstand the question.

The way to make this work is put a nickel plated copper stunt double in place of the shunt fuse.
The stunt double should be the same dimensions as the busbar.

Each battery should be fused as close as possible to the positive terminal.
Each branch circuit should also be fused at the distributor.
The fuse in the shunt is kinda pointless in a properly fused system anyway.
Especially in a 24 volt or higher system with LFP batteries.

 

[BillCaswell]

It is common for a busbar to have a total rating that is different than the per-connection rating.

With a 4-lug 1000A busbar, you can not have 1000A going in on two of the lugs and 1000A going out of two of the lugs, but you could have 500A going into two lugs and 500A coming out of two lugs.

I get that the total throughput can not exceed 1,000 amps, which may be a combination of, for example two 500 amp connections going into the lynx power in. Both sources = 500 amp each x 2 to give 1,000amps. But if the max fuse that one can find is 800 amp, per advice from Victron, then how is this a 1,000 amp system?

 

[FilterGuy]

how is this a 1,000 amp system?

Simple.... You can have as much as 1000amp going in and out. However, all 1000A will not be through one lug, it will be split between lugs.

As I said above, I have seen other busbars where the total current capacity is greater than the current rating for any one connection.

 

[629658]

I get that the total throughput can not exceed 1,000 amps, which may be a combination of, for example two 500 amp connections going into the lynx power in. Both sources = 500 amp each x 2 to give 1,000amps. But if the max fuse that one can find is 800 amp, per advice from Victron, then how is this a 1,000 amp system?

View attachment 131317View attachment 131316

That is 1000 amps from 4 connections per the photo above. 250 amps per connection so buy 250 amp fuses to make your connections. I personally used 300 amp Mega fuses.

 

[BillCaswell]

Simple.... You can have as much as 1000amp going in and out. However, all 1000A will not be through one lug, it will be split between lugs.

As I said above, I have seen other busbars where the total current capacity is greater than the current rating for any one connection.

I get this. I am focused on the lynx shunt not supporting more than an 800amp fuse. That to me is the bottleneck. Won't the fuse blow when you exceed the current rating of the fuse, in this case using the Victron fuse of 325 amps, or a Littelfuse @800amp.

That is 1000 amps from 4 connections per the photo above. 250 amps per connection so buy 250 amp fuses to make your connections. I personally used 300 amp Mega fuses.

Yes, I understand. I am referring to the lynx shunt. See the middle unit in my pictures.

 

[629658]

I get this. I am focused on the lynx shunt not supporting more than an 800amp fuse. That to me is the bottleneck. Won't the fuse blow when you exceed the current rating of the fuse, in this case using the Victron fuse of 325 amps, or a Littelfuse @800amp.

Yes, I understand. I am referring to the lynx shunt. See the middle unit in my pictures.

You do not have to worry about that fuse because it’s just fusing the small amount of power required by the shunt itself. If you look closely I chose to use the Victron smart shunt and mine is attached. If you’re using this for a battery bank to an inverter you are paying a lot for stuff you do not need. You actually only need a Victron Power in ( maybe 2 of them depending on how many batteries) and a smart shunt. You do not need a power in, Lynx shunt and a Lynx distributor.

Also the shunt whichever way you go is only attached to the negative buss. The positive buss is passed straight through to the power in and distributor so no fusing needed. Same with the negative except the shunt sits in the middle still no fusing needed. The only fused thing is the power needed to operate the shunt and it’s software.

 

[FilterGuy]

I get this. I am focused on the lynx shunt not supporting more than an 800amp fuse. That to me is the bottleneck. Won't the fuse blow when you exceed the current rating of the fuse, in this case using the Victron fuse of 325 amps, or a Littelfuse @800amp.

Got it. I was not following before sorry. Yes. When the shunt is there the system's continuous current is limited to the fuse size.

 

[OzSolar]

The positive buss is passed straight through to the power in and distributor so no fusing needed. Same with the negative except the shunt sits in the middle still no fusing needed. The only fused thing is the power needed to operate the shunt and it’s software.

That fuse in the lynx shunt is going to see 100% of the system current.

 

[629658]

That fuse in the lynx shunt is going to see 100% of the system current.

Incorrect

 

[629658]

Got it. I was not following before sorry. Yes. When the shunt is there the system's continuous current is limited to the fuse size.

That is totally incorrect see my explanation above. I have one and so do hundreds of others. No, absolutely no shunt is fused for the loads or rated current flow. The only fused connection for ANY shunt is for the power lead to power the shunt itself.

 

[629658]

That fuse in the lynx shunt is going to see 100% of the system current.

Do you even have a shunt?

 

[629658]

A shunt is a shunt no matter how it is packaged. It’s a measuring device that is inserted inline on the negative pole only. There is no positive pole connection. A small power lead is used to power the shunt itself. In the case of the the lynx shunt the power for the shunt is taken from the positive buss fused and then to the shunt itself. so if you have doubts a simple google search is all that’s necessary. I guess Victron forgot to include the 500amp fuse in their diagram.

 

[OzSolar]

Do you even have a shunt?

It appears that you have no experience with this particular shunt. No current will flow across it until a fuse is installed.

 

[629658]

It appears that you have no experience with this particular shunt. No current will flow across it until a fuse is installed.

This is simply a shunt in a form factor that will attach to the Lynx system. Current flow is not necessary across the red terminals. Voltage is necessary to power the shunt. All current flow is across the negative (black) only. It is installed on the end and not the middle so positive current can power the shunt itself but the entire 1000a bus current is not intended to flow through the Red lugs. The ENTIRE negative current must flow through the shunt (black lugs). It functions and is wired the exact same way as any other shunt.

6. Installation

www.victronenergy.com

 

[629658]

Personally I’d return the shunt and the distributor purchase a Victron smart shunt $150 and add it to a Victron Power In or two save yourself hundreds and accomplish exactly what you want.