Wires and fuses. Please help me to make sure nothing goes up in flames.

[WNCGUY]

Since I am such a NEWBIE, please help give me confidence this won't blow up on me, I welcome your thoughts and suggestions.

This system will be in a minivan.


206ah battery
Cables 2/0. 4' round trip to/from busbars.
Fuse 225-amp battery mounted thermal fuse block.

Inverter 220 watt.
Cables 2/0. 4' round trip to/from busbars.
Fuse 200-amp mounted next to positive bus bar.

12v vehicle battery positive terminal to Victron 12/12-30
Cable #6, 4' long
Fuse 60-amp at 12v battery
Cables #6 to/from Victron. 14' round trip to/from busbars
Fuse 60-amp at positive bus bar.

DC fuse box, rated for 100-amp max
Cables #2. 4' round trip to/from bus bars
Fuse 125-amp at positive bus bar.

 

[John Frum]

206ah battery
Cables 2/0. 4' round trip to/from busbars.
Fuse 225-amp battery mounted thermal fuse block.

Inverter 220 watt.
Cables 2/0. 4' round trip to/from busbars.
Fuse 200-amp mounted next to positive bus bar.

2200 watts / .85 conversion efficiency / 10 volts low cutoff = 258.823529412 service amps
258.823529412 service amps / .8 fuse headroom = 323.529411765 fault amps

12v vehicle battery positive terminal to Victron 12/12-30
Cable #6, 4' long
Fuse 60-amp at 12v battery
Cables #6 to/from Victron. 14' round trip to/from busbars
Fuse 60-amp at positive bus bar.

DC fuse box, rated for 100-amp max
Cables #2. 4' round trip to/from bus bars
Fuse 125-amp at positive bus bar.

Assuming pure copper with 105C insulation...
6 awg can take a 100 amp fuse
2 awg can take a 200 amp fuse
2/0 awg can take a 300 amp fuse

What is ' battery mounted thermal fuse block' ?

 

[WNCGUY]

2200 watts / .85 conversion efficiency / 10 volts low cutoff = 258.823529412 service amps
258.823529412 service amps / .8 fuse headroom = 323.529411765 fault amps

I believe you are telling me the inverter cable will require a 325-amp fuse.

What amp fuse will the battery cable require?

Assuming pure copper with 105C insulation...
6 awg can take a 100 amp fuse
2 awg can take a 200 amp fuse
2/0 awg can take a 300 amp fuse

What is ' battery mounted thermal fuse block' ?

Correct all cables will be pure wire,105C insulation.
I think you are telling me the maximum fuse size allowed for the 6, 2, and 2/0 cables?

6 awg. The Victron manual calls for 10mm2 cable protected by a 60 amp fuse. 6 awg is the closest to 10mm2 without going to an undersize wire.
I assumed, perhaps incorrectly that the wire to the bus bar should also be protected by a 60 amp fuse?

2 awg. My Blue Sea ST blade fuse box arrived today. My understanding is 4-6 awg wire is to be used and it must be protected by no more than a 125 amp fuse

2/0 awg. If 2/0 awg can only take a fuse up to 300 amps and your math indicates "323.529411765 fault amps" I take this to mean I need to use larger cables at the inverter and battery, perhaps 3/0?

Please bear with me, correct me where I am wrong, I am only now starting to learn and know I have so much to grasp.

 

[John Frum]

View attachment 88447View attachment 88448


I believe you are telling me the inverter cable will require a 325-amp fuse.

What amp fuse will the battery cable require?

Lets make that 4/0 awg with a 400 amp class-t fuse.
Lets make the inverter cable 4/0 awg with a 350 amp fuse.
This will aid in fault isolation

Correct all cables will be pure wire,105C insulation.
I think you are telling me the maximum fuse size allowed for the 6, 2, and 2/0 cables?

Yes.
Its my general policy to fuse to the wires rating as higher rated fuses have lower resistance.

6 awg. The Victron manual calls for 10mm2 cable protected by a 60 amp fuse. 6 awg is the closest to 10mm2 without going to an undersize wire.
I assumed, perhaps incorrectly that the wire to the bus bar should also be protected by a 60 amp fuse?

Please provide a product link so that we can see what the maximum wire size the cage clamps can accept.
How long is the round trip distance for the circuit?

2 awg. My Blue Sea ST blade fuse box arrived today. My understanding is 4-6 awg wire is to be used and it must be protected by no more than a 125 amp fuse

Use 6 awg and a 100 amp fuse.

2/0 awg. If 2/0 awg can only take a fuse up to 300 amps and your math indicates "323.529411765 fault amps" I take this to mean I need to use larger cables at the inverter and battery, perhaps 3/0?

300 amps is the largest fuse I suggest for 2/0.
But it can take about 330 amps https://baymarinesupply.com/calculator

As stated above lets use 4/0 awg with a 350 amp fuse for the inverter circuit.

The big problem is your battery can only deliver ~100 amps continuous.

SOK Battery

SK12V100,SK12V206,SK12V206H,SK24V100,SK48V100

www.sokbattery.com

You should have 3 of them in parallel.

Is your inverter made by Giandel?

 

[WNCGUY]

Lets make that 4/0 awg with a 400 amp class-t fuse.
Lets make the inverter cable 4/0 awg with a 350 amp fuse.
This will aid in fault isolation

Ok, understood, to use,
Battery 4/0 with 400 amp class-t fuse
2200 watt inverter 4/0 cable with 350 amp fuse

Yes.
Its my general policy to fuse to the wires rating as higher rated fuses have lower resistance.

Please provide a product link so that we can see what the maximum wire size the cage clamps can accept.

Victron 12/12-30 non-isolated manual

https://www.victronenergy.com/upload/documents/Manual-Orion-Tr-DC-DC-Smart-Charger-Non-Isolated-EN-NL-FR-DE-SV-CZ.pdf

How long is the round trip distance for the circuit?

Existing design is
2' 12v battery positive to Victron.
7' Victron negative to bus bar.
7' Victron positive to busbar.

Use 6 awg and a 100 amp fuse.

OK understood. Blue Sea DC fuse box.
Use 6 awg and a 100 amp fuse.

300 amps is the largest fuse I suggest for 2/0.
But it can take about 330 amps https://baymarinesupply.com/calculator

As stated above lets use 4/0 awg with a 350 amp fuse for the inverter circuit.

The big problem is your battery can only deliver ~100 amps continuous.

SOK Battery

SK12V100,SK12V206,SK12V206H,SK24V100,SK48V100

www.sokbattery.com

You should have 3 of them in parallel.

Is your inverter made by Giandel?

I haven't purchased an inverter or any other hardware, I first want to get the design finalized.
I selected the 2200watt Gandel inverter because I thought Will Prowse recommend this but I no longer see it on his list of budget recommendations, perhaps I made the mistake. I see now Will recommends GOWISE 1500 watt and 2000 watt as budget inverters.

I don't need 2200 watt inverter in the van but though it would be nice to be able to power my home fridge and a light and tv in the event of a power outage.

A 1500 inverter should meet my needs in the van and guess this may also let me run my home fridge, lite and tv during a power outage. I hate to ask we restart this exercise but would you mind sizing for a 1500 watt inverter?

Previously you asked me "What is ' battery mounted thermal fuse block' ?" I intend to mount on the 206ah battery.

https://www.amazon.com/gp/product/B07LC3Q4LD/ref=ox_sc_saved_title_4?smid=AMVRK92LFYKXB&psc=1

 

[Murrayt]

Do not mount fuse on the battery it is a fire risk as it can melt down and cause a much larger battery fire

 

[Zil]

My 2000 W inverter draws 150 amperes when draws are on high. The simple math calls for 167 amperes. If I upgrade that for 2200 W inverter the simple math calls for 183 amperes. Let us say 200 Amp 8 feet round from battery. 2/0 awg less than 3% voltage drop, ampacity 330 amperes. My 300 amp fuse at the battery terminal with the 250 amp fuse at the BusBar works as well as could be. 4/0 is way overkill for 12 volts less than 3000W inverter less than 10 feet round from the battery.
BusBar; https://www.bluesea.com/products/2104/PowerBar_600A_BusBar_-_Four_3_8in-16_Studs
Fuse; https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A
Or combine; https://www.bluesea.com/products/5196/MRBF_Surface_Mount_Fuse_Block_-_Common_Source
If LiFePo battery you should use a Class-T fuse at the battery positive. If lead acid I use these MRBF terminal fuse.
A quality fuse properly selected for the service location and ampacity of the cable will not melt down or cause a fire.

 

[Levo]

Okay, just read all of the above and my concern seems relevant to this thread. I have been stress testing my new installation.

280Ah LiFePO4 battery (200A BMS)
TBS Powersine inverter, 1300 continuous/1600 10 min/2500 surge https://tbs-electronics.com/wp-content/uploads/2019/10/PS1000-1800D-EN-REVA.pdf
Battery to bussbars, about 12"
Bussbars to inverter, about 18"
2AWG copper wire

I ran a "nominal" 1500w heater, showed 148A @ 12.5v draw on my meter for 15 minutes (twice as long as I would ever max out). Yes, the red light came on the inverter, but it did not hiccup and kept on running throughout, no trips or overheating. However, I think the rating is very conservative on this high quality unit so that is not my main concern. The cooling fan ran for a couple of minutes after and no delay re-starting the inverter.

When running with battery straight to bussbars (3/16 x 1-1/4 copper) there was barely any discernable warming of the wires after 15 minutes. But, after mounting the Littelfuse 175A (yes, I know MRBF is better) at the battery terminal, significant heating occurred in 5 minutes or so, right at the fuse location and slightly on the wiring.

I was very careful with fuse mounting, solid copper (polished, 3/16" x 1" flatbar), clamped very tightly, but there is apparently significant resistance there.

I understand that single 2AWG should be good up to 180A continuous current. Given that the heating occurs right at/around the fuse, would the heating be reduced/eliminated by upping the wire size, or is there something else I am missing regarding the fuse assembly? As indicated, all stayed cool without the fuse. If wire upsizing is the only solution okay, but would hate all that work and (some) expense if it is not really the problem. Thanks.

 

[John Frum]

Okay, just read all of the above and my concern seems relevant to this thread. I have been stress testing my new installation.

280Ah LiFePO4 battery (200A BMS)
TBS Powersine inverter, 1300 continuous/1600 10 min/2500 surge https://tbs-electronics.com/wp-content/uploads/2019/10/PS1000-1800D-EN-REVA.pdf
Battery to bussbars, about 12"
Bussbars to inverter, about 18"
2AWG copper wire

I ran a "nominal" 1500w heater, showed 148A @ 12.5v draw on my meter for 15 minutes (twice as long as I would ever max out). Yes, the red light came on the inverter, but it did not hiccup and kept on running throughout, no trips or overheating. However, I think the rating is very conservative on this high quality unit so that is not my main concern. The inverter fan ran for a couple of minutes after and no delay re-starting.

When running with battery straight to bussbars (3/16 x 1-1/4 copper) there was barely any discernable warming of the wires after 15 minutes. But, after mounting the Littelfuse 175A (yes, I know MRBF is better) at the battery terminal, significant heating occurred in 5 minutes or so, right at the fuse location and slightly on the wiring.

I was very careful with fuse mounting, solid copper (polished, 3/16" x 1" flatbar), clamped very tightly, but there is apparently significant resistance there.

I understand that single 2AWG should be good up to 180A continuous current. Given that the heating occurs right at/around the fuse, would the heating be reduced/eliminated by upping the wire size, or is there something else I am missing regarding the fuse assembly? As indicated, all stayed cool without the fuse. If wire upsizing is the only solution okay, but would hate all that work and (some) expense if it is not rally the problem. Thanks.

Zcase fuses are supposed to be used with carrier that has an insulated bolt.

 

[John Frum]

I understand that single 2AWG should be good up to 180A continuous current. Given that the heating occurs right at/around the fuse, would the heating be reduced/eliminated by upping the wire size?

A larger wire will conduct a bit more heat away from the problem area which is the fuse or joinery adjacent the fuse but its does not directly address the problem.

 

[John Frum]

This is a good carrier if the stud and fuse are both m8

Littelfuse 0FHZ0202Z SMZ Series, M8 Stud Mount ZCASE Fuse Holder | Waytek

Littelfuse 0FHZ0202Z SMZ Series, M8 Stud Mount ZCASE Fuse Holder with Fuse Cover, 400A, 80VDC is in stock and ready to ship. Order today!

www.waytekwire.com

 

[John Frum]

understand that single 2AWG should be good up to 180A continuous current.

Since the largest commonly available fuse you can use on 2 awg is 200 amps the service current is 160 max.

 

[Levo]

Zcase fuses are supposed to be used with carrier that has an insulated bolt.

This is mounted with insulated bolt, (hard, non-compressible lexan washer underneath, double heatshrink on the bolt)

 

[John Frum]

This is mounted with insulated bolt, (hard, non-compressible lexan washer underneath, double heatshrink on the bolt)

Have you got an ir camera?
The heat bloom might be informative.

 

[Levo]

Have you got an ir camera?
The heat bloom might be informative.

Yes, I am sure it would, but no I have not.

 

[John Frum]

Yes, I am sure it would, but no I have not.

I'm using 100 amp zcase fuses but the max current I've put through them is ~70 amps.
They did not get above ~35C in ~25C ambient.

 

[John Frum]

If it were me I would use some sandpaper on the mating surfaces followed by some contact cleaner.
See if that helps.
Supposedly even an eyelash can make for a bad joint.

 

[Levo]

I could be mistaken, but I think the fuses up to 250A have M8 hole, so with clearance and insulation, only the M6 or 1/4" bolt will fit. Does the extra clamping force make such a difference? It is clamped very tightly and well centred.

I can't see any significant difference between the manufactured mount and mine - in fact mine is heavier. Also I'll need to dig and check availability in Canada. The shipping from USA always costs WAY more than the product and some vendors won't send them here.!

But yes, the problem is located there, so I that is where I'll focus. As I said, would hate to re-wire unnecessarily

 

[John Frum]

I could be mistaken, but I think the fuses up to 250A have M8 hole, so with clearance and insulation, only the M6 or 1/4" bolt will fit. Does the extra clamping force make such a difference? It is clamped very tightly and well centred.

I can't see any significant difference between the manufactured mount and mine - in fact mine is heavier. Also I'll need to dig and check availability in Canada. The shipping from USA always costs WAY more than the product and some vendors won't send them here.!

But yes, the problem is located there, so I that is where I'll focus. As I said, would hate to re-wire unnecessarily

I use m8 zcase fuses on m8 studs.

Littelfuse 0FHZ0007Z FHZ Series ZCASE Fuse Holder | Waytek

Littelfuse 0FHZ0007Z FHZ Series ZCASE Fuse Holder, 7 Stud Assembly with Bolts and Bus Bars, 400A is in stock and ready to ship. Order today!

www.waytekwire.com

Littelfuse 3298600.ZXSTA ZCASE Single MEGA® Starter Fuse, 600A | Waytek

Littelfuse ZCASE Single MEGA® Starter Fuse, 600A, 32VDC, 3298600.ZXSTA is in stock and ready to ship. Order today!

www.waytekwire.com

Littelfuse 3298125.Z ZCASE Single MEGA® Starter Fuse | Waytek

Littelfuse 3298125.Z ZCASE Single MEGA® Starter Fuse is in stock and ready to ship. Order today!

www.waytekwire.com

 

[John Frum]

Does the extra clamping force make such a difference?

I doubt there is much difference between tight enough and too tight.