Are my fuses are rated correctly?

[MrPsychedelic]

So I think I usually way undersize my fuses, but Id rather be safe then sorry. So I'm reaching out to see if I should keep as is, or up size them.

I have 2 48V batteries with 200A bms's. They run to a common bus bars with 2awg cables, then negative goes to the lynx distributor with a 1/0 cable and positive with a 1/0 cable goes to a 150A class T and after that a Victron on/off switch then to the positive terminal on the lynx distributor. At the distributor I will have a 150A mega fuse.

I will then run a 1/0 cable from the lynx with a 100 amp fuse to the Victron 5k multi plus.

My next cable set is my solar. 2s2p 540w panels. They are rated at 12.97A(Imp) and Isc at 13.85A, so I have a 30A midnite solar breaker with 10awg wire, from the other side of the breaker will be 6awg wire to the SCC. From the SCC with 6 awg wire it will connect to the lynx with a 60A fuse(smallest I could find in 58V+)

The last wire I will have from the lynx is for my 48V-12V converter. It runs at 60A max, so I will be using a 6awg wire running to that with a 60A fuse on the lynx distributor.

Does all that sound good or should I increase some of the fuses?

 

[rodrick]

Fuses and breakers are for protection of your wires so sizing to the max amp rating of the wire and you should be fine if your near the max all the time size the wire up and fuse according to the larger wires rating

 

[MrPsychedelic]

Fuses and breakers are for protection of your wires so sizing to the max amp rating of the wire and you should be fine if your near the max all the time size the wire up and fuse according to the larger wires rating

That's what I felt I was doing. I use blue seas wire size chart, but I've been told that's not entirely accurate and that wires can handle more then that chart shows. So I have no idea what to believe

 

[rodrick]

That's what I felt I was doing. I use blue seas wire size chart, but I've been told that's not entirely accurate and that wires can handle more then that chart shows. So I have no idea what to believe

Wires have a rating on them like 75C 90C ect so wires of the same gage can handle different amps depending on the insulation used so you will see some different ratings due to that

Best bet is go by the manufacturers recommendation for their products they don’t want any issues so it should work fine

Just give yourself some headroom when sizing the wire don’t run right at the top end of its limit it doesn’t cost much more and I feel it’s good insurance against having a problem imo

 

[MrPsychedelic]

Wires have a rating on them like 75C 90C ect so wires of the same gage can handle different amps depending on the insulation used so you will see some different ratings due to that

Best bet is go by the manufacturers recommendation for their products they don’t want any issues so it should work fine

Just give yourself some headroom when sizing the wire don’t run right at the top end of its limit it doesn’t cost much more and I feel it’s good insurance against having a problem imo

Most of the wires I bought had a chart with them so I'm just going a little under the max rating of the wire for the fuses.

As far as the class t on my batteries, is it okay to just have 1 250A class T on the 1/0 cable after the common positive bus bar, or do I need to put (2) 150A class Ts before the common bus bar, 1 for each battery?

I've always fused after the batteries are wired together but not sure if I've been doing it wrong

 

[rodrick]

The best way is to fuse each battery or a dc breaker rated correctly on each if you want a way to shut off the power and a main fuse going to your inverter also stay with the class t fuses when dealing with 48 volt systems

 

[MrPsychedelic]

The best way is to fuse each battery or a dc breaker rated correctly on each if you want a way to shut off the power and a main fuse going to your inverter also stay with the class t fuses when dealing with 48 volt systems

So fuse each battery with a 150A class t, then I won't need the 250A class t after the bus bar correct?

 

[rodrick]

So fuse each battery with a 150A class t, then I won't need the 250A class t after the bus bar correct?

I would still use a fuse on the main line coming off the bus bar because with multiple batteries those 150 amps fuses could overload youre line if something happened so I would fuse that line according to its rating also I'm a belt and suspenders type of guy

 

[MarioP]

Is there such a thing as putting too large of a fuse?
If you have a 48v/5000w inverter, that's right about 104amps.
With 125% safety factor, that's right about 130amps.
As I understand, there is realistically speaking no such thing as too large of a conductor/wire.
But what about fuse or breaker?
Is 160, 200, 250 amp fuse too large to put on a system?

 

[HRTKD]

Is there such a thing as putting too large of a fuse?
If you have a 48v/5000w inverter, that's right about 104amps.
With 125% safety factor, that's right about 130amps.
As I understand, there is realistically speaking no such thing as too large of a conductor/wire.
But what about fuse or breaker?
Is 160, 200, 250 amp fuse too large to put on a system?

Yes, you can put in too large of a fuse that doesn't blow soon enough to protect the wire.

I don't use wire gauge charts. Instead, I use a wire gauge calculator that takes into account voltage, amperage and distance.

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

The forum recommends fusing each battery. But often we bring the two battery cables together and then put in a single fuse. Do as we say, not as we do.