Fuses and Breakers are doing my head in !!!

[Urge38]

You would think that circuit protection would be fairly Stright forward, right??

well, I am finding it a worse task than choosing the right inverter/charger!!

so, I am trying to build some protection from my four rack batteries to my inverter. (eack rack battery is 48v 100a)

Two wires going from my rack cabinet busbar to my inverter charger, quite basic, but the problem lies in finding the correct protection,

I've read that due to possible huge discharge currents, some fuses if blown can form an arc, and it's very difficult to close that arc, and hence why some fuses are filled with silica to distinguish that arc. OK I follow that bit, but then on some spec sheets certain fuses state a 48W loss !!!! what's that all about?? are they saying using there fuse I will lose 48w as some kind of usage loss ???

breakers are a topic in them self's again,

you struggle to find a suitable breaker for my size of system BUT THEN realise that as I have a inverter/charger, the breaker will see current passing in both direction!!

more head damage finding a suitable breaker.

I want my mummy lol lol

 

[SeaGal]

... but then on some spec sheets certain fuses state a 48W loss !!!! what's that all about?? are they saying using there fuse I will lose 48w as some kind of usage loss ???

Really? I find that hard to believe. 48W would generate a significant amount of heat.

We use a Jean-Muller breaker, like this...

Fuse-switch-disconnector KETO size 00 body (battery isolator)

Renugen solar panels wind turbines

www.renugen.co.uk

... available in 40 to 200A ratings to suit your inverter.

edited to add: uses Jean Muller NH fuses...

Fuse links - JEAN MÜLLER

www.jeanmueller.de

 

[SeaGal]

To clarify... direction is irrelevant, a classic fuse is not directional.

All you need to do is find out what is the max charge or discharge rate of the inverter.... take the max of those if they differ.

Then choose the appropriate DC cable to handle that current, with plenty to spare. You will want to minimise losses on that connection so keep it as short as practical and size the cable according to current and distance.

Then choose a fuse size for your disconnector that is at least 25% less than the d.c. cable's rating, but (obviously) higher than the max of charge or discharge current that your inverter can handle.

 

[Steve_S]

Most typically, we suggest Equal Length Battery Cables to Busbars and same from the busbars to the Inverter. This is to keep resistances etc all in line, as well, it is important to note that these DC wires should be kept together to prevent EMI / RFI. You'd be surprised at the magnetic & electrical fields on DC, can be quite noisy. Ask any HAM Operator ;-)

With 48VDC we typically suggest Class-T or MEGA Fuses. Also we highly recommend a Fuse/Breaker for each battery. Additionally a DC Switch that is capable of disconnecting the batteries from everything.
* Many Server/Telecom Rack type battery packs have breakers built-in but not all.

FUSES are simple enough, they do NEED to be mounted into a holder and come in various formats. There are even Busbars with Fuse Holders built-in and then we have Victron Lynx that does that and more.

Breakers come in TWO Flavours:
Standard Bi-Directional Breakers which are common but being outplaced by Polarized Breakers (some regions now require these to pass certification). There are No Issues with Polarized breakers BUT the rules have to be followed for them.

A switch is commonly installed, to enable you to cut power off entirely to the battery bank for service, maintenance etc. Because you are using 48V this reduces your choices but not by much. It is important that whatever switch you choose that it can handle the Amperage being passed through it.

See Here for Victron BusBars (including Lynx) and Switch etc.

DC Distribution systems & Fuses - Victron Energy

Victron Energy's DC distribution systems monitor the state of charge of your battery and the state of each fuse. View products now.

www.victronenergy.com

Because you did not state if you are using an AIO or Component based system I will post two reference images for you to refer to. Additionally, I should point out that "Typically" we suggest you do not exceed 250A Draw from a Battery System (12,000W on 48V).

Hope it helps, Good Luck.

 

[JJJJ]

Victron Lynx

Very nice unit. Multiple ways it can be used and has a very nice feature set.

 

[Urge38]

Really? I find that hard to believe. 48W would generate a significant amount of heat.

We use a Jean-Muller breaker, like this...

Fuse-switch-disconnector KETO size 00 body (battery isolator)

Renugen solar panels wind turbines

www.renugen.co.uk

... available in 40 to 200A ratings to suit your inverter.

edited to add: uses Jean Muller NH fuses...

Fuse links - JEAN MÜLLER

www.jeanmueller.de

thanks for the link, they do look good and cheap enough unfortunately I my system requires a 250A rating, and as you say, there's only goes up to 200a

 

[Urge38]

To clarify... direction is irrelevant, a classic fuse is not directional.

All you need to do is find out what is the max charge or discharge rate of the inverter.... take the max of those if they differ.

Then choose the appropriate DC cable to handle that current, with plenty to spare. You will want to minimise losses on that connection so keep it as short as practical and size the cable according to current and distance.

Then choose a fuse size for your disconnector that is at least 25% less than the d.c. cable's rating, but (obviously) higher than the max of charge or discharge current that your inverter can handle.

I was referring to a directional breaker.

 

[Urge38]

Most typically, we suggest Equal Length Battery Cables to Busbars and same from the busbars to the Inverter. This is to keep resistances etc all in line, as well, it is important to note that these DC wires should be kept together to prevent EMI / RFI. You'd be surprised at the magnetic & electrical fields on DC, can be quite noisy. Ask any HAM Operator ;-)

With 48VDC we typically suggest Class-T or MEGA Fuses. Also we highly recommend a Fuse/Breaker for each battery. Additionally a DC Switch that is capable of disconnecting the batteries from everything.
* Many Server/Telecom Rack type battery packs have breakers built-in but not all.

FUSES are simple enough, they do NEED to be mounted into a holder and come in various formats. There are even Busbars with Fuse Holders built-in and then we have Victron Lynx that does that and more.

Breakers come in TWO Flavours:
Standard Bi-Directional Breakers which are common but being outplaced by Polarized Breakers (some regions now require these to pass certification). There are No Issues with Polarized breakers BUT the rules have to be followed for them.

A switch is commonly installed, to enable you to cut power off entirely to the battery bank for service, maintenance etc. Because you are using 48V this reduces your choices but not by much. It is important that whatever switch you choose that it can handle the Amperage being passed through it.

See Here for Victron BusBars (including Lynx) and Switch etc.

DC Distribution systems & Fuses - Victron Energy

Victron Energy's DC distribution systems monitor the state of charge of your battery and the state of each fuse. View products now.

www.victronenergy.com

Because you did not state if you are using an AIO or Component based system I will post two reference images for you to refer to. Additionally, I should point out that "Typically" we suggest you do not exceed 250A Draw from a Battery System (12,000W on 48V).

Hope it helps, Good Luck.

View attachment 150625

View attachment 150626

Very helpful

my system is very basic

four 48v 100a rack batteries
A schneider conect XW + 12000w max for one minute, 8500w for 30 minuets. 6000 cont

no solar, charging from a gen through the Schneider

 

[WattAboutThat]

https://watts247.com/product/dc-breaker-4p-125a-battery-disconnect/

i am still learning, so do not rely on my suggestion:

but my understanding is that this breaker has 4 connections in and out, each capable of 125A.

If you had a bus bar (comb style) to put on each side (in and out), you could achieve 500A, which is 25% over your max (400 x 1.25).

so this might solve your problem
using 4 batteries in parallel

my issue is i have 6 in parallel
and can not find a breaker like this
to handle 600A, let alone 750A or 800A
for a 25% or 33% cushion.

 

[Urge38]

I personally don't like lots of under size breakers, connected as one.

I have decided NOT to use a breaker but a suitable fuse instead.

I see to many people using breakers as on off switches,

I somehow trust a capable fuse more than I do a breaker.

when a fuse goes, it simply goes, when a breaker goes, it can cause a fire.