What fuses will my system need?

[Viewtiful_Jon]

Hello, I have a very small system I have not set up yet as I do not need it quite yet and want to make sure everything is protected first. I will list all the components in the order that they will be connected once the system is completed. I will be physically connecting the solar panel last.

400W Solar Panel ( 1 single panel )
1 meter MP4 cables (10AWG)
150v/40a Charge controller (Epever one with metal case)
8AWG Cables
12v 100ah Lithium Battery (will likely get a second when I know everything is running smoothly)
Cables that come with the inverter I think that they are 4AWG
1000w Inverter

I do not have the MP4 or the 8AWG cables yet they are just the ones I plan to purchase and am pretty sure are correct for the system.

Will a small system like this need to be protected by fuses and if so what type and where should I place them?

 

[John Frum]

Yes you need fuses.

The cables the come with cheap inverters are usually crap and should be thrown out with the packing peanuts.
Quality 4 awg pure copper wire with insulation rated for 105C and proper lugs will serve you well.
I suggest you use busbars to connect your system.
For a small system like this.
I like this fused busbar for the positive side.

MRBF Surface Mount Fuse Block - Common Source - Blue Sea Systems

Easily and economically satisfies ABYC 7 circuit protection rule by mounting on a 3/8 battery post, battery switch or bus bar.

www.bluesea.com

And this for the battery

MRBF Terminal Fuse Block - 30 to 300A - Blue Sea Systems

Easily and economically satisfies ABYC 7 circuit protection rule by mounting on a 3/8 battery post, battery switch or bus bar.

www.bluesea.com

This would be fine for the negative busbar

MaxiBus 250A BusBar - Four 5/16"-18 Studs - Blue Sea Systems

Insert-molded stainless steel studs an optional fully enclosed insulating base and cover.

www.bluesea.com

for the inverter branch circuit 4 awg with 150 amp fuse.
For the battery 2 awg with 200 amp fuse.
For the solar charge controller 8 awg with 50 amp fuse.
You don't need a fuse between the pvanel and the solar charge controller but a means of disconnect is useful.

 

[Zil]

Lithium batteries can pack a punch in a short circuit. You must have a catastrophic fuse on the battery positive very near the battery terminal. The engineers I read all recommend the use of a Class-T fuse. But I believe the MRBF fuses have sufficient interrupt capacity. I am not an electrical engineer.
Fuses protect wires, we fuse to the ampacity of the wire we use. We need to reduce voltage drop, and larger fuses have less voltage drop. Fuse to protect the wire. Important to a device that is as voltage sensitive as an inverter.
I wish I could give more "thumbs up" on post number two above.

 

[Viewtiful_Jon]

Sorry, it took so long to get back to you but I was confused about where the fuses were all going as my original plan was to just have everything connected in series so the Inverter would have been connected directly to the battery but from what you are describing I think you are suggesting something like in the first image I have included. (I stole the image and added the values of the fuses and AWG values to confirm I have everything correct.)


With the surface mount fuse block would I plug the wire that is coming from the charge controller directly into a 50 amp fuse on it and then it would have a separate 150 amp fuse which I would use for the Inverter?
If so would the battery have a separate 200 amp fuse as part of the fuse block or just the terminal fuse?
I decided to put a second picture for this. (100% Original image)

Hopefully, I am on the right track for what you are describing.

 

[John Frum]

All correct, the feeder position on the positive busbar is not fused because that wire is fused as close as possible to the battery positive terminal.
Just for fun I made some ascii art.

legend {
    nnn|NNN| { fused busbar position where nnn is wire guage in awg and NNN is fuse rating in amps }
    nnn|UUU| { un-fused busbar position where nnn is wire guage in awg }
    | { un-fused busbar }
    <-> { bi-directional current flow }
    -> { uni-directional current flow }
    <- { uni-directional current flow }
}
positive
002|UUU|<->mbrf_fuse<->battery<->shunt<->|
004|150|->inverter---------------------->|
008|050|<-solar_charge_controller<-------|
016|001|->shunt_power------------------->|
                                  negative

 

[Viewtiful_Jon]

Thank you once again, I will have a look around to find all the pieces I need to finish, cannot use the links provided as in the UK but they seem easy to find.

 

[John Frum]

Thank you once again, I will have a look around to find all the pieces I need to finish, cannot use the links provided as in the UK but they seem easy to find.

Since you are in the UK.
16 awg ~= 1.5mm2
8 awg ~= 10mm2
4 awg ~= 25mm2
2 awg ~= 35mm2