Should I parallel 2 x 125A fuses?

[ianganderton]

Good morning

I’m trying to minimise connections in the system I’m installing and have found this

SafetyHub 150 Fuse Block - Blue Sea Systems

Ignition-protected fuse blocks capable of consolidating and protecting multiple 1A to 200A circuits.

www.bluesea.com

I have a 12v 2000W epever inverter

IPower-Plus Series(220/230VAC) 500~5000W Pure Sine Wave Inverter

IP-Plus is a high-frequency pure sine wave inverter that can convert 12/24/48VDC to 220/230VAC and power the AC loads. Ranging from 500~5000W

www.epever.com

In the inverter manual it specifies 2 x 125A breakers

Manual - https://www.epever.com/wp-content/uploads/2021/05/IPower-Plus-Manual-EN-V3.1.pdf#page23

The fuse/distribution box takes midi fuses which max out at 200A. Could I parallel 2 x 125A midi fuses with equal length 10 or 16mm2 cables (pretty short, 30cm) going to the inverter?

This solution will radically reduce the number of connections I will need to build which to my mind will radically reduce the number of potential failure/resistance points. Plus the circuits will be dramatically more compact further reducing resistance

 

[OzSolar]

The fuse/distribution box takes midi fuses which max out at 200A. Could I parallel 2 x 125A midi fuses with equal length 10 or 16mm2 cables (pretty short, 30cm) going to the inverter?

I might be missing something but that sounds like your asking the fuse box that's rated for 200 amps to deal with 250 amps and that's before you add any other loads to it.

And you might double check your ampacity charts. I think you're a few sizes to small but I'm in the USA this more familiar with AWG than mm2.

 

[MrThisIsME]

I might be missing something but that sounds like your asking the fuse box that's rated for 200 amps

I think the unit is rated at 600amps and each branch circuit can carry 200amps (the limit of the AMI fuse?). If it where anything other than Blue Sea I would say no way that can handle 600amps. A nice compact unit nethertheless.

Good morning

I’m trying to minimise connections in the system I’m installing

You state such and then ask about running two cables where you should be running one. Did you purchase the Blue Sea unit already? Are you planing to use the ATC fuses to run other DC applications?

If it where me, I would run from the battery to a single 250amp fuse and then inverter. Before doing such I would check on if the larger cable lugs required for a single run would fit on the invertor. Maybe that is why they are are suggesting two cables with smaller lugs.

Never understood why we constantly see two fuses / breakers in such applications.

 

[John Frum]

What system voltage have you selected?
What is the continous wattage rating of the inverter you have selected?
Since that unit supports remote switching do you intend to control it with a Victron battery protect or similar?

 

[John Frum]

The oem is littelfuse.
Will probably be cheaper under the littelfuse name.

Littelfuse 880089 LX Series Power Distribution Module | Waytek

Littelfuse 880089 LX Series Power Distribution Module, 4 MIDI Fuse Block, 60V, Max 600A, IP59K is in stock and ready to ship. Order today!

www.waytekwire.com

 

[ianganderton]

What system voltage have you selected?
What is the continous wattage rating of the inverter you have selected?
Since that unit supports remote switching do you intend to control it with a Victron battery protect or similar?

12V - most watts consumed will be DC

The inverter will likely be used for strong 2000W loads only for a short period and occasionally

The inverter is rated for 2000W continuous. I won’t use it above that

Not planning on using a battery protect

Will use the epever remote monitor mt75 to control it manually

 

[ianganderton]

The oem is littelfuse.
Will probably be cheaper under the littelfuse name.

Littelfuse 880089 LX Series Power Distribution Module | Waytek

Littelfuse 880089 LX Series Power Distribution Module, 4 MIDI Fuse Block, 60V, Max 600A, IP59K is in stock and ready to ship. Order today!

www.waytekwire.com

That’s interesting but probably difficult to get here in New Zealand

This is the local supplier

Blue Sea Safety Hub Fuse Block

Blue Sea Safety Hub Fuse Block

www.lusty-blundell.co.nz

 

[John Frum]

The inverter is rated for 2000W continuous. I won’t use it above that

Since its a high frequency inverter its surge capacity will likely be rated in milli-seconds so you can't really use it beyond its rating.

Assuming your are not controlling it with a battery protect here is the math...
2000 ac watts / .85 conversion factor / 10 volts low cutoff = 235.294117647 service amps
235.294117647 service amps / .8 fuse headroom = 294.117647059 fault amps

you could go as low as 70mm2 cable and a 300 amp fuse
Probably should go up at least one size for efficiency sake

 

[ianganderton]

Since its a high frequency inverter its surge capacity will likely be rated in milli-seconds so you can't really use it beyond its rating.

Assuming your are not controlling it with a battery protect here is the math...
2000 ac watts / .85 conversion factor / 10 volts low cutoff = 235.294117647 service amps
235.294117647 service amps / .8 fuse headroom = 294.117647059 fault amps

you could go as low as 70mm2 cable and a 300 amp fuse
Probably should go up at least one size for efficiency sake

Dies Lifepo4 go as low as 10A? Certainly not without the internal BMS kicking in

 

[ianganderton]

Since its a high frequency inverter its surge capacity will likely be rated in milli-seconds so you can't really use it beyond its rating.

Assuming your are not controlling it with a battery protect here is the math...
2000 ac watts / .85 conversion factor / 10 volts low cutoff = 235.294117647 service amps
235.294117647 service amps / .8 fuse headroom = 294.117647059 fault amps

you could go as low as 70mm2 cable and a 300 amp fuse
Probably should go up at least one size for efficiency sake

Manual says surge rating is 4000W for 5 seconds

Inverter low voltage protection is 10.5V. Hmmmm

 

[John Frum]

The datasheet says these units have 2x surge for 5 seconds.
That is pretty good for a high frequency inverter.
Combined with the remote switching this is a nice unit.

Dies Lifepo4 go as low as 10A? Certainly not without the internal BMS kicking in

That is the common pack voltage disconnect trigger but since the pack is going to be top balanced one of the cells will disconnect on low cell voltage first.
I checked the manual and the inverter lvd is 10.8 volts.
That is usually +-.5 volts.

https://www.epever.com/wp-content/uploads/2021/05/EPEVER-Datasheet_IPower-Plus-220v-1.pdf

 

[ianganderton]

I’d done my maths on 2000W + 15% @ 12V = 192A
Trying to keep everything compact with short wiring and the cable size came up 50mm2 with lower than 1% loss

I’m re- evaluating that now with the lower voltages I’m getting an understanding off

Will look at the Victron battery protect as an option

In the manual it’s specifying 2 x 125A DC breakers. Is that because 250A breakers are difficult to find?

Im under the impression that fuses are preferred in a mobile application

Is 2 fuses the same as 2 breakers?

The type of loads I expect to use on the inverter are
High (only intentionally when battery is full and weather forecast is good)
2000W kettle
Induction cooktop
NB not at the same time

Low
Battery chargers

I really like how few electrical pathway joints there are in that fuse/distribution box. That just makes so much sense to me. As a concept it just seems reliable and low resistance.

 

[ianganderton]

And you might double check your ampacity charts. I think you're a few sizes to small but I'm in the USA this more familiar with AWG than mm2.

Yeah that’s a mistake. I’m planning on 50mm2 from the battery to the inverter

 

[John Frum]

I’d done my maths on 2000W + 15% @ 12V = 192A
Trying to keep everything compact with short wiring and the cable size came up 50mm2 with lower than 1% loss

You are not accounting for inverter efficiency and the low voltage disconnect is ~11 volts not 12.
You are also not accounting for fuse headroom.
50mm2 is too small.
70mm2 is "by the book"
Not sure what the next metric size up is but that is what I would be looking at with a fuse to match.

In the manual it’s specifying 2 x 125A DC breakers. Is that because 250A breakers are difficult to find?

No its because the manual is silly.
There is no reason not to use a suitably sized single wire and fuse.

Im under the impression that fuses are preferred in a mobile application

Fuses are more compact and cheaper.
Conversely quality breakers are more expensive and larger.
For a 12 volt system such are yours that bluesea combo block is really a good fit.

The type of loads I expect to use on the inverter are
High (only intentionally when battery is full and weather forecast is good)
2000W kettle
Induction cooktop
NB not at the same time

Low
Battery chargers

I really like how few electrical pathway joints there are in that fuse/distribution box. That just makes so much sense to me. As a concept it just seems reliable and low resistance.

Me too.

 

[John Frum]

All of my math is based on pure copper wire with insulation rated to 105C.
Nobody wants there wires getting hotter than boiling water so experienced folks tend to up-size the wire.
Heat is lost energy.

 

[ianganderton]

For a 12 volt system such are yours that bluesea combo block is really a good fit.

Apart from the fact I can’t get fuses bigger than 200A that will fit it

 

[John Frum]

Apart from the fact I can’t get fuses bigger than 200A that will fit it

Now I get what you are driving at.
Use 2x 35mm2 with 150 amp fuses for the positive side of the inverter branch circuit.
Use 70mm2 for the negative side of the inverter branch circuit.
The battery to fuseblock(feeder) circuit is fused at the battery.
Use the next size up from 70mm2 with appropriate fuse.
ANL fuses are fine for a 12 volt LFP battery.

 

[ianganderton]

OK, been working on this problem a bit and pivoted slightly





I still need to check all the cable sizes. I know the SCC to battery and load are incorrect

The Lynx Power In with DIY fuse conversion solves a lot of my concerns around reducing any connections where possible while making a neat robust expandable system

I'll use the blue sea link bus (i've got a pair) to connect the battery disconnect and the shunt to the Lynx bus bars



The other price of the puzzle solved is I've been reading the Invert manual and the low voltage disconnect is user configurable



I've just been looking at the battery data sheet



If I set the low voltage disconnect to something like 12.3V that will protect everything against high amps caused by low battery volts and current draw (1C, 200A). Not sure what to set the reconnect at yet

2000W + 15% inverter inefficiency = 2300W

2300W / 12.3V = 187A which gives me 25% headroom

I think my maths is correct and I'm feeling like this is finally starting to look like something I'm happy with

 

[ianganderton]

Ok so now I’ve run into the opposite problem

The mega fuses needed in the lynx don’t come less than 100A

I need something 40 to 50A for my charge controller/dc loads connection

So the 40 to 50A mega fuse conundrum.

Google pulled up thus post

48 v 40 amp mega fuse?

hi everyone. I’m stuck. I can’t find any fuses with small enough amperage to work with my victron 150/35 mppt and the lynx distributor. The wire size I’m using was 10mm going out. I thought a 40 or 45 mega fuse would do. Can’t get one for 48v system.......So I’m looking to use the max wire that...

diysolarforum.com

rmaddy said:
The Blue Sea Systems wire/fuse chart shows that a single, unbundled, 105ºC 6AWG wire (a bit smaller than 16mm²) can handle up to 125A. Therefore a high quality 16mm² wire can handle more than 125A. So as long as your 100A fuse is rated for 48V then you should be good.

Any thoughts?

 

[ianganderton]

Ok so now I’ve run into the opposite problem

The mega fuses needed in the lynx don’t come less than 100A

I need something 40 to 50A for my charge controller/dc loads connection

So the 40 to 50A mega fuse conundrum.

Google pulled up thus post

48 v 40 amp mega fuse?

hi everyone. I’m stuck. I can’t find any fuses with small enough amperage to work with my victron 150/35 mppt and the lynx distributor. The wire size I’m using was 10mm going out. I thought a 40 or 45 mega fuse would do. Can’t get one for 48v system.......So I’m looking to use the max wire that...

diysolarforum.com

Any thoughts?

Disaster averted, found lower ampage fuses https://www.repco.co.nz/en/globes-b...k-acx6518bl/p/A1327153?kwSearch=OEX Mega Fuse,