Super basic question Re: bus bars

[metalheaddoc]

I am looking to build a simple 400w 12v system. Am I supposed to use bus bars to connect everything? Is there anything that shouldn't go through a bus bar other than PV input? And do fuses go after the bus bar near the target? (i.e. fuse right before battery positive terminal)

For example:
Charge controller --> bus bar --> Battery
Battery --> bus bar --> Inverter
Battery --> bus bar --> 12v fuse block

Basically everything after the charge controller goes thru the bus bar?

 

[Rednecktek]

The simplest way would be to go:

Battery Pos -> Fuse -> Pos Bus Bar -> Everything else
Battery Neg-> Shunt -> Neg Bus bar -> Everything else

There shouldn't be any reason you can't connect your charge controller, inverter, fuse block, etc right to the bus block. If you wanted to fuse individual components beyond that you would put the fuses as close to the power source as you can and then out from there, i.e a fuse right at the SCC positive output or a fuse at the bus block before the inverter.

All a bus block does is give you a convenient place to stick all the different size wires together so you don't have a huge wire nut.

 

[DerpsyDoodler]

I am looking to build a simple 400w 12v system. Am I supposed to use bus bars to connect everything? Is there anything that shouldn't go through a bus bar other than PV input? And do fuses go after the bus bar near the target? (i.e. fuse right before battery positive terminal)

For example:
Charge controller --> bus bar --> Battery
Battery --> bus bar --> Inverter
Battery --> bus bar --> 12v fuse block

Basically everything after the charge controller goes thru the bus bar?

Fuses protect wires.

Refer to the TLDR at the bottom if you just want to know deets for your system.

Battery connects to bus bar with a wire rated to carry enough current for the entire system + 25%. That wire gets fused at the same rating.

The bus bar needs to be rated to carry enough current for the entire system. every wire coming off or going to the bus bar should be fused according to its individual circuit load.

40A charge controller? wire for 40+25% A of current and fuse for the same amount.

250A inverter? wire for 250+25% A (or just follow the manual's recommended fuse/wire rating if its a quality inverter) and fuse for the same amount.

50A DC distribution block? 50+25%A and fuse for the same.


TLDR;

400W / 12v = ~33A

33 + 25% = ~40A <---current to use for sizing fuse and wire rating off the battery.

If this is a 12v DC system only, you can forget about a bus bar (unless you're paralleling multiple batteries, and even then it is not strictly necessary).

Battery -- Fuse -- Main Disconnect --
DC Distro Panel --
fuse -- load 1
fuse -- load2
fuse -- charge controller
etc

You will connect your charge controller and all your loads through the dc panel, utilizing its fuses to properly fuse each circuit.

Remember that fuses protect wires.

Reference:
Reading researching and verifying much of the information found on this forum.

 

[A.Justice]

On my first, simple, low(er) power build, I connected everything directly to the batteries and BMS, I only used bus bars for the cells themselves.

My only loads were a single, fused, 12v "cigarette lighter" port, and the fused inverter; both were hooked to the positive terminal.

My "rule" is no more than two things attached to a single screw terminal (excluding sensor wires). If you are only using an inverter on your system, personally, I would skip the bars.

As said above, don't forget to fuse. The bar itself, AND the things attached to it.