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Finding the right size bus bar

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JonL

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I need to find the right size bus bar for my system.
I will have two strings of solar, one string of three panels 300 W at 24 V. Another string of four panels 320 W at 24V connected to a combiner box lead to a Victron 150/85 charge controller.
I will have four 150w panels =600 W wired at 24 V in series/parallel. This will be hooked up to a Renogy 60 amp charge controller.
I will want to add more panels in the future. Possibly another 1.5 kW. Will need a third charge controller most likely.
The inverter charger will be a Victron Multiplus 24/3000/70-50 120V
This will be my first time connecting all this together and will need to size the bus bar properly. Can anybody recommend A brand and size for this system?
Also does it matter what size shunts you have? Thanks Jon
 
I came across this website and chart data on busbars.
stormpowercomponents.com

Technical Library

Technical library of busbar engineering resources - Free downloads - Product guides, Ampacity charts and Whitepapers
stormpowercomponents.com stormpowercomponents.com
 
Blue Sea Systems is a reputable brand, Bussmann (another very reputable brand) is the maker of some of Blue Sea's components, not sure if they make the busbars or not. I believe they go as high as 1000A which is obviously overkill for most applications. 300A-500A would be more than enough for most applications, but you need to do the math. You can figure out the size yourself in much the same way you would figure out wire size, figure out the max potential current in your system, get a busbar that is rated for more than that.

Also does it matter what size shunts you have? Thanks Jon
Click to expand...

Are you asking this as a standalone question, or are you asking if your busbars should be sized relative to your shunts?

If its an isolated question, the basic answer I've heard is that you want to size your shunt so that: max continuous current flowing through it is roughly 2/3 to 3/4 of the shunts rating. So for instance if the max current is 200A a 300A shunt would be ideally sized.
 
Thanks, I was thinking along the same lines of 300 to 400, unfortunately they don’t make those - so I have to go to 600. Expensive!
 
JonL said:
Thanks, I was thinking along the same lines of 300 to 400, unfortunately they don’t make those - so I have to go to 600. Expensive!
Click to expand...
There is also the DIY route if you have the means, and want to trade effort for $$. A busbar is essentially just a big piece of copper. But the marine busbars are nice and convenient because they have the cover, the tin plating, and the work is already done for you. I feel you about the price though. Maybe someone knows of a decent budget alternative that doesn't skimp.
 
Don’t know enough about it to know if that would work, since I am a rookie I need to play it safe. They always say that oversize everything. ?
 
Thanks. In the past I just would wire everything to the batteries, I guess this isn’t the best idea. Now that I have expensive lithium batteries, I’m trying to configure the best and safest setup.
 
When I got my busbar, I wish I’d spent more time figuring out the size of the posts. I planned on using seven posts, so I got two 8 post bus bars with each of the 8 posts 3/8 inch studs. THese were huge, about 12“ across. I probably only needed 3/8” studs on two posts on each busbar, and could have went with one that had screw in terminals.

I ended up going with Blue Sea. I’d at first ordered a 250 amp audio bus bar With 5/16th studs, but decided to replace it with a Blue Sea Bus bar.

The sheet that came with mine said I could connect more than one lug to each stud, which probably could have kept my busbar even smaller, but I’d already had installed it when I found out. Not sure I would install more than one lug for each stud.
 
JonL said:
Thanks, I was thinking along the same lines of 300 to 400, unfortunately they don’t make those - so I have to go to 600. Expensive!
Click to expand...
The problem with a 600 Amp shunt is it will not be accurate for most of the time because you are only using less thatn 50% of its capacity versus and 200 Amp shunt that will be accurate 90% of the time. When you are pulling 200 Amps in a small system like yours, you will want to reduce consumption more than know exactly how much you you are consuming.
 
I found one for 500 Amps? I guess I don’t really understand what you’re talking about-sorry.
The shunt will be for reading the Victron battery monitor ?
 

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If you want accuracy buy a shunt that is closer to the operating range you are going to be most concerned about consumption. A 200 Amp shunt can take bursts of 300 Amps. A 500 Amp shunt will be less accurate at measuring 200 Amps than a 200 Amp shunt. They make them in all sizes.
More importantly size your system correctly and then find a shunt when you have a better idea what you are going to do with the results it reports.
 
Ampster said:
If you want accuracy buy a shunt that is closer to the operating range you are going to be most concerned about consumption. A 200 Amp shunt can take bursts of 300 Amps. A 500 Amp shunt will be less accurate at measuring 200 Amps than a 200 Amp shunt. They make them in all sizes.
More importantly size your system correctly and then find a shunt when you have a better idea what you are going to do with the results it reports.
Click to expand...

Can we define bursts

Are we talking roughly seconds? tens of seconds? minutes? tens of minutes
 
Dzl said:
Can we define bursts
Click to expand...
I think the system the OP is talking about is 24 volts and a 3kW inverter. He would have to tell us how he is going to see more that 125 Amps. I just think a smaller shunt will be more accurate that a 500 Amp shunt. What has your experience been with shunts?
 
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Ampster said:
I think the system the OP is talking about is 24 volts and a 3kW inverter. He would have to tell us how he is going to see more that 125 Amps. I just think a smaller shunt will be more accurate that a 500 Amp shunt. What has your experience been with shunts?
Click to expand...

I don't have an in depth understanding of shunts, the rule of thumb I've heard (in the SBMS0 manual and elsewhere) is that continuous current should be roughly 2/3 or 3/4 of the shunts rating.

I interpreted this to mean the max continuous current you expect to ever see, but I'm not positive on that, if a shunt were more tolerant of surges of say a few minutes (and it might be, since its basically a big hunk metal), than you might be able to fly a little closer to the sun and have better accuracy.

This isn't an area I feel confident enough to have an opinion beyond repeating the basics that I've read elsewhere.
 
Ampster said:
You have a choice but I haven't seen an inexpensive analog shunt in years. Have you Googled shunt to see what your choices are? I found some at 250 Amps.
Click to expand...
Blue sea systems had a 200 amp shunt that I ordered. I canceled the 500 amp one, thank goodness. ?
 
Update: How ironic, the Victron battery monitor they sent me arrived today and it already has a 500 amp shunt in the box. The manufacturer must feel that this is OK? ?
 
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