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Do bus bars have a place? Where do I put the fuses?

solitas777

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So I recently bought this system and I have two 175 watt solar panels to power 24watt 100amp battery (2 100amp 12v battlebornes). I was thinking of getting a second charge controller to put 4 100 watt panels on the roof of my cargo trailer and have them in serial.

1) Do I use a bus bar to go from both batteries directly into the main unit through a bus bar?

2) Should I put a fuse between the battery and the bus bar? 150amp be ok for both right?

3)Do I need to put fuses between the solar panels and the charge controllers?


There seems to be a million different ways systems can be set up and I've ready many books but I still find the whole thing a little intimidating and confusing.

Thanks!
 
Do I use a bus bar to go from both batteries directly into the main unit? Should I put a fuse between the battery and the bus bar? 150amp be ok for both right?
(1) maybe, I don't fully understand what you are building/describing
(2) yes
(3) I don't know, maybe/probably, a fuse is sized to be larger (>1.25x) than the max load, and smaller than the wire used (the main purpose of a fuse is to protect the wire, it is an intentional weak point). Put another way, whatever size fuse you choose the wire must have a higher rating than it.

Do I need to put fuses between the solar panels and the charge controllers?
Only if the panels are wired in parallel, otherwise a single breaker or disconnect switch is commonly used.

There seems to be a million different ways systems can be set up and I've ready many books but I still find the whole thing a little intimidating and confusing.
Yes and yes :) there are a million ways and it can be intimidating and confusing. My advice, spend a bit of time trying to understand the concepts before focusing on the specific design. One reason there are a million ways is because a lot of things are very situational/contextual, so the design depends on the context, the use-case, and the priorities, another reason is because there are many ways to solve a given problem, and another reason is because for every valid solution (and some invalid ones) there is someone arguing its the best option, which makes it hard for a newbie like you or I.

This is why I think trying to learn the fundamentals, and the concepts is so important. If you can learn just on a basic level, the theory of how the system works, and what components do, and how energy and electricity work, it empowers you to understand a lot more about how to design whats right for you. Most youtubers and many resources focus on the how, not the what and the why, but these latter questions are very important to understanding the how.


So circling back to your questions, in light of the above focus on concepts.

A fuse is an engineered weak point, and an 'overcurrent protection device.' Its purpose is to fail safely before other parts of your system can fail unsafely.
A busbar is just a conductor (like a wire), its useful for distributing or combining. They can be a useful organizational tool in your design.

(y)
 
(1) maybe, I don't fully understand what you are building/describing
(2) yes
(3) I don't know, maybe/probably, a fuse is sized to be larger (>1.25x) than the max load, and smaller than the wire used (the main purpose of a fuse is to protect the wire, it is an intentional weak point). Put another way, whatever size fuse you choose the wire must have a higher rating than it.


Only if the panels are wired in parallel, otherwise a single breaker or disconnect switch is commonly used.


Yes and yes :) there are a million ways and it can be intimidating and confusing. My advice, spend a bit of time trying to understand the concepts before focusing on the specific design. One reason there are a million ways is because a lot of things are very situational/contextual, so the design depends on the context, the use-case, and the priorities, another reason is because there are many ways to solve a given problem, and another reason is because for every valid solution (and some invalid ones) there is someone arguing its the best option, which makes it hard for a newbie like you or I.

This is why I think trying to learn the fundamentals, and the concepts is so important. If you can learn just on a basic level, the theory of how the system works, and what components do, and how energy and electricity work, it empowers you to understand a lot more about how to design whats right for you. Most youtubers and many resources focus on the how, not the what and the why, but these latter questions are very important to understanding the how.


So circling back to your questions, in light of the above focus on concepts.

A fuse is an engineered weak point, and an 'overcurrent protection device.' Its purpose is to fail safely before other parts of your system can fail unsafely.
A busbar is just a conductor (like a wire), its useful for distributing or combining. They can be a useful organizational tool in your design.


(y)
Great reply Thank you. I'm just trying to figure out how to get to different charge controllers charging 2 different solar arrays to power one battery bank and I was wondering if I am supposed to go through bus bars to do that.
 
Great reply Thank you. I'm just trying to figure out how to get to different charge controllers charging 2 different solar arrays to power one battery bank and I was wondering if I am supposed to go through bus bars to do that.
Busbars sound sensible in that context.
 
I was wondering if I am supposed to go through bus bars to do that.
Theoretically no. However busbars do make it easier when they have multiple connection points for different input/outputs.
Without a busbar connect the extra CC to the same connection to the battery as the other CC.
If you add a busbar there is no need for a fuse between the busbar and the battery.
 
If you add a busbar there is no need for a fuse between the busbar and the battery.
I don't quite follow your logic but I'm not sure I understand what you are saying, can you explain?

Are you assuming the main battery fuse(s) would be at or after the busbar?
 
Unless the cable from the battery positive to the positive buss bar is not very long, there is a need for a fuse at the battery positive.
 
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Are you assuming the main battery fuse(s) would be at or after the busbar?
Fuses, if required, after the busbar.
In op's case a fuse at the pv and another at the busbar if the wire goes through the RV's frame since the flow can be both ways if there is a fault.

Before adding fuses identify what you are trying to protect and whether a fuse gives that protection?
You already have a problem well before that 200amp fuse between busbar and battery blows.
 
Basically a bus bar is desired when you have a lot of things that need to connect to each other. You certainly COULD just have every positive wire with a ring terminal all on the same bolt, but that would be a real pain in the ass to work with if you have to disconnect anything. The bus bar gives you easier access to stuff.

There should absolutely be a fuse or breaker between the bus bar and the MPP, you can ask 10 different people about fuses between the batteries and the bus bars and get 12 answers though. Honestly, sometimes peace of mind is worth a few dollars.

As an example, in my planned re-vamp of my cabin electrical system I've got a Growatt, a paralleled SCC, a couple buck transformers, a desulfator unit, and 3 sets of batteries in parallel. I've got my main breaker between the bus bars and the Growatt, and I'll have a fuse on each battery bank down on the positive lug just in case my batteries try to draw "lopsided" for some unknown reason. In the grand scheme of things a few fuses weren't a huge cost and it gives me peace of mind.

I have a combiner box for my 3s/3p solar setup and it has fuses for each string. Mostly I wanted it to make my life easier for maintenance and troubleshooting as well as cable management, but having the fuses is also a Good Practice so I'm not going to throw them out.

Also, as an American working on foreign built ships, I envy you 220v people. :p
 

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Theoretically no. However busbars do make it easier when they have multiple connection points for different input/outputs.
Without a busbar connect the extra CC to the same connection to the battery as the other CC.
If you add a busbar there is no need for a fuse between the busbar and the battery.
There IS a need for a fuse at the battery positive terminal before the BusBar.
 
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