Fuse and Wire sizing question

[stuntmanmike]

Hey guys Getting everything set up on my van solar build. I was just about to buy wire and ANL fuses, now my overtired head is second-guessing what I am doing. Installed everything thus far in 4awg from the local west marine, and freaked out that it was supposed to be 4/0. I have highlighted in pink what I am working on. I am basing this build off wills blueprint https://www.mobile-solarpower.com/simplified-400-watt-fewer-wires-and-alternator-charging.html which says 4awg.......
Help with the following
1. wire sizing between two 100 amp lithium in parallel. is it on discharge or total
2. is is better to come from POS to a shut off then to a POS bus bar with 2 fuses one to the 125 amp fuse block and the second to the inverter, or just size fuse correctly. At this time I am going to use the inverter cables that came with "doubled up 4awg"
2a or ditch the doubled up wires and go with (_____) size
3. ground the inverter lug 10awg to the back to the negative bus bar and ground the bus bar to the chassis "redundant grounding"?

thanks in advance, trying to do this once....

 

[rmaddy]

You do not have 100A batteries. You probably have 100Ah batteries. A battery's capacity has no bearing on the size of the wires and fuses.

Since your batteries are in parallel for a 12V system then with a 2000W inverter you will have 2000W / 12V / 0.85 = 200A. For that you need at least 2/0 gauge wire. 4AWG is way too small.

I would use a separate fuse for each item. There should be a battery fuse, an inverter fuse, a fuse box fuse, a charge controller fuse, etc.

 

[stuntmanmike]

yes, thanks 2(100AH) batteries typo..... thanks for the quick response.

Hey, my negative bus bar is located near the rear pillar of the van with a convenient factory hole. if I cleaned it with a wire brush and threaded nutsert it should be fine right? I guess I will find out if not

 

[boondox]

yes, thanks 2(100AH) batteries typo..... thanks for the quick response.

Hey, my negative bus bar is located near the rear pillar of the van with a convenient factory hole. if I cleaned it with a wire brush and threaded nutsert it should be fine right? I guess I will find out if not

That really depends on the specifics of the van. On my Transit there are paces that look good but really aren't due to the way the van is constructed. On a rear pillar, probably OK. The manufacturer may have a chart with "blessed" locations for ground. I would rather not use a nutsert. Better would be to clean the paint and use a bolt. However, in my van I have a cable to the battery and do not use the van at all for passing current. Especially in high current applications this is a better way to go.

As to wire size that depends primarily on length of run, voltage and amperage being pulled. Here is a link to a calculator. If you hae any questions roll on back over here and ask.

Circuit Wizard - Blue Sea Systems

 

[stuntmanmike]

That really depends on the specifics of the van. On my Transit there are paces that look good but really aren't due to the way the van is constructed. On a rear pillar, probably OK. The manufacturer may have a chart with "blessed" locations for ground. I would rather not use a nutsert. Better would be to clean the paint and use a bolt. However, in my van I have a cable to the battery and do not use the van at all for passing current. Especially in high current applications this is a better way to go.

As to wire size that depends primarily on length of run, voltage and amperage being pulled. Here is a link to a calculator. If you hae any questions roll on back over here and ask.

Circuit Wizard - Blue Sea Systems

thanks for the calculator.
Ok im intrigued, I also have a transit, the electrical system is later in the build and dont feel like pulling everything to get back. why is it better?

 

[12VoltInstalls]

I have a cable to the battery and do not use the van at all for passing current. Especially in high current applications this is a better way to go.

why is it better?

cleaned it with a wire brush and threaded nutsert it should be fine right? I guess I will find out if not

First thing is you don’t know if the oem battery to chassis cabling will support the loads you may put on it. Typically the only high-amp negative(-) goes to the engine block for completion of the starting circuit.

Second is that a nutsert doesn’t make a secure non-resistive connection where corrosion or just its nature guarantees a good connection (the bolt suggestion is a good one).

IN my van I have a cable to the battery and do not use the van at all for passing current.

As boondock stated he goes to the battery which is best because the home run to the battery gives you a guaranteed known calculatable amp and voltage capacity whereas a vehicle body has many unknowns and is often less than 60A or even 50A from a braided ground strap.

 

[boondox]

thanks for the calculator.
Ok im intrigued, I also have a transit, the electrical system is later in the build and dont feel like pulling everything to get back. why is it better?

The unibody construction with spot welds may not have a good connection. Some of the crossbeams are actually isolated from the bod with foam/glue. Ford has a "BMM" that has all the "blessed" spots. However, as I said, I go straight to the house battery with cable. My DC to DC charger also has a run from the start battery and to the house battery. All DC devices have a complete run to the house battery. The only chassis ground I use is to RF ground my radios.

 

[stuntmanmike]

The unibody construction with spot welds may not have a good connection. Some of the crossbeams are actually isolated from the bod with foam/glue. Ford has a "BMM" that has all the "blessed" spots. However, as I said, I go straight to the house battery with cable. My DC to DC charger also has a run from the start battery and to the house battery. All DC devices have a complete run to the house battery. The only chassis ground I use is to RF ground my radios.

I am assuming that your transit is like mine with the batteries under the driver's seat. and are running some sort of dc to dc charging???? Are you running a2/0 back to the house battery???

 

[Zil]

I was looking at the wire size table. I use marine grade wire. It is rated for higher ampacity than your list indicates. My typical build is: Positive side; Battery -> fuse -> cable -> BusBar -> devices. Each device has a fuse on the BusBar to protect the cable going to that device. Cables and wires are sized using a voltage drop table. Fuses are sized to the awg using a ampacity table. Your question about the fuse size for the Blue Sea fuse block; I use Blue Sea ST fuse blocks. They are rated at 100 amperes maximum. Depending on the distance I may use a 2awg cable for limited voltage drop. I lead that cable from the BusBar with a 200 ampere fuse. If my voltage drop chart determined a 4awg cable I would use a 150 to 160 ampere fuse. I only use marine grade wire. I have noticed the Blue Sea Circuit Wizard has lately been suggesting much heavier cable than before. IE: Suggesting 4/0 rather than the 2/0 I determine from other charts.
I can't see for sure how you connect the panels. Parallel? Do you really have a fuse plus a circuit breaker?
Your 12 volt inverter will need 2/0 cable from battery to inverter, unless it is some unreasonable distance.
It is not a good idea to double cables to carry a heavier load. There will always be an imbalance and a chance of melting a wire.
I use a cutoff switch on the negative side to disable my system. If I wish to work on individual devices or circuits I have each on a fuse to remove.

 

[boondox]

I am assuming that your transit is like mine with the batteries under the driver's seat. and are running some sort of dc to dc charging???? Are you running a2/0 back to the house battery???

No. My start battery to DC to DC charger to house battery run is less than 15 feet. Since my DC to DC charger puts out 40 amps we know that it must use more than that on the input size. So I used 50 amps to calculate. Using 2AWG I get a 2.51% voltage drop which is acceptable. This is why the calculators are important. You may need 2/0 or you may not. Here is another one I use a lot:

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

It shows the calc I used for my run.

 

[stuntmanmike]

I was looking at the wire size table. I use marine grade wire. It is rated for higher ampacity than your list indicates. My typical build is: Positive side; Battery -> fuse -> cable -> BusBar -> devices. Each device has a fuse on the BusBar to protect the cable going to that device. Cables and wires are sized using a voltage drop table. Fuses are sized to the awg using a ampacity table. Your question about the fuse size for the Blue Sea fuse block; I use Blue Sea ST fuse blocks. They are rated at 100 amperes maximum. Depending on the distance I may use a 2awg cable for limited voltage drop. I lead that cable from the BusBar with a 200 ampere fuse. If my voltage drop chart determined a 4awg cable I would use a 150 to 160 ampere fuse. I only use marine grade wire. I have noticed the Blue Sea Circuit Wizard has lately been suggesting much heavier cable than before. IE: Suggesting 4/0 rather than the 2/0 I determine from other charts.
I can't see for sure how you connect the panels. Parallel? Do you really have a fuse plus a circuit breaker?
Your 12 volt inverter will need 2/0 cable from battery to inverter, unless it is some unreasonable distance.
It is not a good idea to double cables to carry a heavier load. There will always be an imbalance and a chance of melting a wire.
I use a cutoff switch on the negative side to disable my system. If I wish to work on individual devices or circuits I have each on a fuse to remove.

thanks... I have been getting my wire from west marine, not the cheapest but they have everything I need. With regards to the panels in parallel with a 20 amp fuse. the circuit breaker is as a shut off not for protection. My DC DC divides up the current 25 amp solar and 25 amps alt. I found that if I disconnect the solar the alt will pull almost 50. most of my highway time has surfboards shading the panels.
Based on your and others bought some 2/0 for the connections

 

[stuntmanmike]

No. My start battery to DC to DC charger to house battery run is less than 15 feet. Since my DC to DC charger puts out 40 amps we know that it must use more than that on the input size. So I used 50 amps to calculate. Using 2AWG I get a 2.51% voltage drop which is acceptable. This is why the calculators are important. You may need 2/0 or you may not. Here is another one I use a lot:

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

It shows the calc I used for my run.

super helpful 2 awg it is

 

[boondox]

super helpful 2 awg it is

As long as your run length, voltage and amps are the same it will work fine. Note that I am close to the maximum acceptable loss of 3% so it wouldn't take much change to put it over the edge.

 

[Zil]

I build rv systems so my advice may need modifying for large S&B systems
Parallel panels. Different fusing requirements with parallel panels.
Here is one from Windy Nation. https://www.windynation.com/jzv/inf/how-properly-fuse-solar-pv-system
That explains what happens if one panel shorts in a parallel array.
I do not agree with that 60amp fuse on the combiner box. I use cable to the controller that can handle all the power the panels can produce. I do use a disconnect switch, not a circuit breaker.
I use this for most 4 panel parallel arrays. https://www.bluesea.com/products/5045/ST_Blade_Compact_Fuse_Blocks_-_4_Circuits They also have one with 8 circuits.

 

[stuntmanmike]

I build rv systems so my advice may need modifying for large S&B systems
Parallel panels. Different fusing requirements with parallel panels.
Here is one from Windy Nation. https://www.windynation.com/jzv/inf/how-properly-fuse-solar-pv-system
That explains what happens if one panel shorts in a parallel array.
I do not agree with that 60amp fuse on the combiner box. I use cable to the controller that can handle all the power the panels can produce. I do use a disconnect switch, not a circuit breaker.
I use this for most 4 panel parallel arrays. https://www.bluesea.com/products/5045/ST_Blade_Compact_Fuse_Blocks_-_4_Circuits They also have one with 8 circuits.

That makes sense, fuse each panel not the total solar input, do you know if the fuse block you recommended is waterproof, "roof mount", or are you running all of the wires through and fusing inside the van????