# Nearing the End - Need Wiring Help



## MoonRiver (Sep 2, 2007)

My questions are in bold, but please don't limit yourself to just those. If I missed anything please point it out. Under I now have (below), I linked to the equipment I either have, have on order, or in the case of the wire, am asking if this is what I should order.

I now have:

2 100Ah 12V LiFePO4 Deep Cycle Batteries
1 Victron BlueSolar PWM Pro C Controller 12/24V-20A (100w solar panel)
1 Victron SmartSolar MPPT 150/60 Solar C Controller ( 2 300w solar panels)
1 Aims Power 2000 Watt Pure Sine Wave Inverter
1 Victron Battery Monitor BMV-712 Smart
2 Renogy 300 Watt 24 Volt Monocrystalline Solar Panels
1 Renogy 100 Watt 12 Volt Monocrystalline Solar Panel
Proposed 1/0 Wiring
I have been trying to wrap my brain around the type of wire, fuse blocks, inline fuses, battery switches, busbars, etc. I can't hold enough information in my short term memory to put it all together.

These will be short runs. 300W panels will be installed on roof of van. From roof to floor of van is 6' approx. Batteries will sit on floor of van with all the other hardware being within a few feet. Cables will be between 18" and 3' (1 way) for connections to battery and wiring from 300w solar panels to MPPT charge controller will be less than 15' (1 way).

Let me say what pieces I think I have figured out, and then correct me where I am wrong or there is a better way.

ETA: I already changed my mind. For these short distances, I think I can use 6 awg wire.

I will use 1/0 wire for everything (except existing solar panel wires). That's it. That's all I've figured out! Everything else seems to depend on 1 or 2 other things.
Let's start with batteries. They will be connected in parallel, so that's 200ah at 12v.

Connected to batteries are:

Battery Monitor with shunt

2000w Inverter
MPPT controller
PWM controller
Fuse block for 12v circuits.
*What can I combine to minimize connections at battery and what is the best way to do this. What do I need in terms of switches, fuses, busbars, etc to connect all these devices to batteries? I also want a way to disconnect the batteries from everything, and I need to protect everything.*

2 300w Solar Panels to MPPT Charge Controller

The 300w solar panels have 40" wires terminated in MC4 connectors. The panels are 40" wide. I need to combine these wires so I have 2 wires going through roof into van. I think I can use the existing wire (cutting off MC4s) up to whatever the combiner is. *What should I use to combine the wires.* It may have to sit under a solar panel and only have about 1.5" clearance from roof to bottom of panel. Then I was planning on using the 1/0 wire from the combiner down to the charge controller. *What do I need to be able to turn off the power coming into the charge controller? And do I need a fuse or circuit breaker and what size? *

Specifications for Renogy 300W Solar Panels
Maximum Power at STC: 300W Maximum System Voltage: 1000VDC
Optimum Operating Voltage (Vmp): 32.25V Open Circuit Voltage (Voc): 39.82V
Optimum Operating Current (Imp): 9.33A Short-Circuit Current (Isc): 9.78A

I'm not worried about the 100w solar panels now. If I need them, I can figure that out after all this gets done.


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## ShannonR (Nov 28, 2012)

This is what we did at our (now burned down) homestead, the schematics were drawn up by a friend at the local solar store. It specifies what gauge wire, length of runs, and where the wires go. Sorry, about the paper being all crumbled and stained, I posted this long after the system was installed and had lost track of this paper for awhile. Hope it helps.
http://hardscrabblehomestead.blogspot.com/2016/08/wiring-schematics-for-main-solar-system.html?m=1


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## ShannonR (Nov 28, 2012)

Oh, and we used a cutoff switch between the panels and charge controller. Real basic.


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## Murby (May 24, 2016)

Your asking the question(s) in the wrong way.. its forcing readers to diagnose your system to figure out what you're doing.


Between the battery and everything else, should be over-current and disconnect components. You can kill two birds with one stone and have fewer connections and less wire with properly rated circuit breakers.

Your wire should be the fine stranded battery cable type. You can use regular stranded wire in your small system but I wouldn't recommend it.

When I go to your panel linked website, I can't see any specs on the panels.. they want me to open my browser to allow all their java script and I won't do that.. Please post the specs for the panels. Volts, amps, etc.


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## MoonRiver (Sep 2, 2007)

Thanks Shannon.

I found that the solar panels have 12 awg leads. I calculated what I needed to go from solar panels to MPPT charge controller and 12 awg will work. Going from MPP controller to battery looks like 8 awg.

The one that is causing me the most trouble is the 2000 w power converter. I don't know what to size for. Is it the max surge power I plan to use? The power inverter will surge up to 4000 w, but I believe the most I need is a little over 1000 for my 5000 BTU ac.


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## ShannonR (Nov 28, 2012)

We had to use heavy, battery cable wire from the batteries to the inverter, if that is what you're asking. Not sure on the size, but it's about the same size you need to wire the batteries themselves together. I would plan to size it for the max surge capacity, because sometimes you will plug something in which you had NO IDEA draws as much voltage as it does.

We combined our wires from the panels at the circuit breaker/shutoff box.


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## MoonRiver (Sep 2, 2007)

Murby said:


> Your asking the question(s) in the wrong way.. its forcing readers to diagnose your system to figure out what you're doing.
> 
> Between the battery and everything else, should be over-current and disconnect components. You can kill two birds with one stone and have fewer connections and less wire with properly rated circuit breakers.
> 
> ...


Please explain things as though all I understand is amps, volts, and power and you will be right on. I don't know things like why you use a fuse instead of a circuit breaker and vice versa. I think I correctly calculated wire gauge for solar panels to charge controller, I kind of think I calculated the wire gauge for charge controller to batteries correctly. I came up with 12 awg for panel to c controller and 8 awg from c controller to battery. That makes sense because I went from 24 to 12 volts, but for a much shorter distance, so 12 awg/2 = 6 awg but shorter distance lets me use 8 awg.

I have no idea how to calculate wire size for connecting 2 batteries together in parallel or how to size wire from batteries to 2000 w inverter.

The specs for the solar panel are at the bottom of the op.


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## Itinerant1 (Jul 23, 2018)

In this link it explains alot and has a wire size calculator. 
http://www.freesunpower.com/index.php


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## Itinerant1 (Jul 23, 2018)

Moonriver,
The panels are operating at a higher voltage than 24v your CC can be converting 39v to 12v.

For instance my 160w 12v panels individually can be 18.6v, 8.6a (22.5v voc) in my 2 panel series that doubles to 37.2v (45v voc). Then 4 sets parallel 45v. After the CC does it's thing it's can be feeding 80a into the batteries but the norm is 65-75a.
Here is what I use coming from the solar and then from the CC.


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## MoonRiver (Sep 2, 2007)

Itinerant1 said:


> In this link it explains alot and has a wire size calculator.
> http://www.freesunpower.com/index.php


Thanks, but it doesn't help me. All the calculators assume you know what numbers to enter. If I knew what numbers to enter, I wouldn't have had to ask for help.

The calculator I like best is http://circuitwizard.bluesea.com/. But I still don't know what values to enter for battery cables and the cable from battery to inverter. I think I can figure out all the other ones.


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## MoonRiver (Sep 2, 2007)

Itinerant1 said:


> Moonriver,
> The panels are operating at a higher voltage than 24v your CC can be converting 39v to 12v.
> 
> For instance my 160w 12v panels individually can be 18.6v, 8.6a (22.5v voc) in my 2 panel series that doubles to 37.2v (45v voc). Then 4 sets parallel 45v. After the CC does it's thing it's can be feeding 80a into the batteries but the norm is 65-75a.
> Here is what I use coming from the solar and then from the CC.


I used Optimum Operating Voltage (Vmp): 32.25V for the solar panels. I was able to determine that 12 awg would work from solar panels to charge controller. It's the battery cables and the cable from batteries to inverter that are the problem.


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## Itinerant1 (Jul 23, 2018)

You have the #s from the panels or batteries and distance of run.


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## Itinerant1 (Jul 23, 2018)

What does your inverter require it should say?

I'm trying to learn (searching) the forum procedure for posting images I would should show how my solar, breakers, inverter, batteries are wired to give an idea. The difference is that my whole 5th wheel is wired with a sub panel so the inverter runs everything except my hot water tank in the rv.


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## MoonRiver (Sep 2, 2007)

Itinerant1 said:


> What does your inverter require it should say?
> 
> I'm trying to learn (searching) the forum procedure for posting images I would should show how my solar, breakers, inverter, batteries are wired to give an idea. The difference is that my whole 5th wheel is wired with a sub panel so the inverter runs everything except my hot water tank in the rv.


If it's a file on your PC, use upload a file (red box below). If it is stored on the web, just click the image icon and then paste the url of the image into it.


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## Murby (May 24, 2016)

MoonRiver said:


> Please explain things as though all I understand is amps, volts, and power and you will be right on. I don't know things like why you use a fuse instead of a circuit breaker and vice versa.


You can use a circuit breaker or a fuse... I like breakers because they also act as disconnects and you don't have to spend money to replace the fuse.. 



> I think I correctly calculated wire gauge for solar panels to charge controller, I kind of think I calculated the wire gauge for charge controller to batteries correctly. I came up with 12 awg for panel to c controller and 8 awg from c controller to battery. That makes sense because I went from 24 to 12 volts, but for a much shorter distance, so 12 awg/2 = 6 awg but shorter distance lets me use 8 awg.


How many amps from panels to charge controller?
How many amps from controller to batteries?



> I have no idea how to calculate wire size for connecting 2 batteries together in parallel or how to size wire from batteries to 2000 w inverter.


1/0 wire is too small.. From the batteries to the inverter, you'll need 2/0 wire.. Not 2 gauge, but 2/0 or ( 00 ) or (0.36x diameter copper which works out to just under 70sq mm of area) 2000 watts @ 12 volts is about 166 amps but probably a bit less since your batteries will probably operate in the 12.5 to 13.5 volt range. A 150 amp DC rated breaker should work fine for you.. 

Make sure your cable lugs are the right size, don't try to use inappropriate lugs that are too big or too small.. that's a big no no and can generate higher resistances and cause hot spots.

If you draw 166 amps from those two tiny batteries, you're going to tax the crap out of them and probably give them coronary artery disease and shorten their life. It is my personal opinion, based on experience and knowing how manufacturers tend to push their technical specs, that those two batteries are not big enough to power a 2000 watt inverter at full power. I'd make sure you don't push that inverter past 1200 watts. 

Also, if you plan on drawing large currents though that inverter on a regular basis, you better make sure you have external ventilation and cooling hooked up.. they don't like getting hot. And for that matter, if your panels are only 1.5 inches from the roof, they are going to have thermal problems as well if you're not driving down the road. Solar panels de-rate their output when they heat up. When its 90 degree's outside, mine lose almost 15%, at 95 degrees, they lose almost 20%.. and mine have great airflow under them. Roof mounted panels are even worse and since your's are mounted flat(?), there's no thermal siphoning action going on so the heat just builds up under them.



> The specs for the solar panel are at the bottom of the op.


Are you wiring in series or in parallel?


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## MoonRiver (Sep 2, 2007)

Itinerant1 said:


> You have the #s from the panels or batteries and distance of run.


But when you wire 2 batteries together in parallel, what numbers do you use? Doesn't it depend on the current that is being drawn? And how do you determine what that number is?

With the inverter, if I have a 2000 w inverter that surges up to 4000 w, do I have to wire for the surge as it is of short duration? I plan on using the inverter to run a window ac which draws about 50 amps at 12 v, but surges higher when compressor kicks in. So do I wire for the full 4000 w surge capacity of inverter, the 2000 w rating of the inverter, 500 w for the running air conditioner, or 1000 w for the surge or the possibility I run the ac and the microwave at the same time? And then would that be 500w for ac + 1100 for microwave or 1000w for ac surge + 1000 for microwave? 

This is the kind of stuff I can't find anywhere.


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## MoonRiver (Sep 2, 2007)

Murby said:


> ?


How many amps from panels to charge controller? *Panels are 300 watts each, so 2 * 300w/24v = 25a*
How many amps from controller to batteries? *24/12 * 25a = 50 a*.

If you draw 166 amps from those two tiny batteries, you're going to tax the crap out of them and probably give them coronary artery disease and shorten their life. *The air conditioner is about 50 amps and surging when compressor kicks in. Microwave is about 1100w or about 85a. A 1500w inverter would have been enough, but I decided to go with the 2000 as it was sold by Battle Born and they will provide help configuring if needed.*

And for that matter, if your panels are only 1.5 inches from the roof, they are going to have thermal problems as well if you're not driving down the road. *There are some grooves in the roof, so some areas will be about 2" and some about 1 1/2".*

Are you wiring in series or in parallel? *Batteries and panels both in parallel.*


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## ShannonR (Nov 28, 2012)

MoonRiver, are you really planning to run your air conditioner on this system? Personal experience talking here.... cheaper to just run that off the generator and not tax your system to the max. The batteries aren't going to appreciate that, at ALL. There is quite a surge when the compressor in those kicks on, also... I tried it, with a larger system too, and that was a no-go.


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## Itinerant1 (Jul 23, 2018)

6/2 & 3/0 used. Copper bar stock on batteries.
In the upper right corner Manual trip 48v DC breakers - 50a (solar in), 120a (solar out) . These can be manually tripped if something needs to be worked on (have not had to yet).
The box on the left is the bms for the batteries thats why the cables run in and out going to inverter/ batteries.


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## Itinerant1 (Jul 23, 2018)

Murby he's bought a victron 150/60 at best he'll get clip at 60a but bet he doesn't see over 50a with 600w more in the 40a range with panels flat and heat from the van roof.


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## Murby (May 24, 2016)

Itinerant1 said:


> Murby he's bought a victron 150/60 at best he'll get clip at 60a but bet he doesn't see over 50a with 600w more in the 40a range with panels flat and heat from the van roof.


The 2/0 wire is the connection between the batteries and inverter.. a 2000w inverter will yank around 166 amps from those batteries when fully loaded.

Going from the panels to the controller is not the same.. its a lot easier. If the panels are wired in parallel then he can get away with 12 ga wire to handle less than 10 amps.. although since the voltage is so low, I'd probably recommend jumping up to 10ga or even 8ga to avoid losses. 

65 volt DC breakers are easy to find on Ebay.. I bought a couple of 65v breakers rated for 175 amps for $20.. and they're new and not made in China.

Going from your controller to the batteries, you're going to want heavier wire as the controller will drop the voltage and drastically raise the current.. For a 60 amp draw, you're probably going to want to use a 4ga wire, and I'd suggest going with a 3ga. That will pass the 60 amps quite nicely.

This is why 12 volt systems suck eggs.. all the wires have to be huge. It is current that causes wear and tear and heat, not voltage.. The higher the voltage, the less the current and the easier the system runs.

One other note, it is wise to avoid the standard stranded wire on the big stuff.. You want to use battery cable or the stuff that's used on Arc welding equipment.. Its the same size wire, but the individual strands of copper are far far smaller and make for better connections and more flexibility.


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## Itinerant1 (Jul 23, 2018)

This is why he needs to understand the wire calculator.
I'm not going to look up his inverter install directions but I'll bet it says what is recommended. The same with his charge controller I'll sure they have some formula to use.
It was in my Magnum inverter and Magnum charge controller for formulas to figure what wire is needed.


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## Murby (May 24, 2016)

Itinerant1 said:


> This is why he needs to understand the wire calculator.
> I'm not going to look up his inverter install directions but I'll bet it says what is recommended. The same with his charge controller I'll sure they have some formula to use.
> It was in my Magnum inverter and Magnum charge controller for formulas to figure what wire is needed.


Those formulas are meant for bare minimum standards with "acceptable losses".. This means that to save money, a lot of standards and practices will accept losses in the 5% range.. and most people don't care if they turn on their load and have to pay an extra 5% in energy costs from the grid.. But for solar, that's a lot of energy being lost to the ever present laws of physics..

My system pushes 25 amps at full power back to the grid.. I could have gotten away with #10 or #8 ga wire but I would have suffered >3% and I wasn't good with that.. At #6ga, those losses came down to around 1.8% or something.. So I went with #4 and ended up with just 0.78%.. 

There's just no substitute for big wire...


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## Itinerant1 (Jul 23, 2018)

I'm all for overkill if you can afford it. Being grid tie like you are the return can be justied.
In a van like the OP all his runs are very short and feeding into battery/ inverter, which he said everything will be near each other no need for overkill or trying to feed a dead lead battery. If he has lived on or used lead batteries the difference in charging/ discharging will be a slighly different animal meaning during charging they will take everything that can be thrown at it getting a recharged battery fast no hours of absorb or firing a generator up/ plugging into a power outlet to get it back to full.
The discharge of the 2 lfp batteries will be nice and flat as long as his 2000w inverter can handle the wattage. What he won't be able to do is run multiple high draw items at the same time.

OP, break down your system in sections for wiring.
1. Panels to combiner.. easy enough the wires are on the panels.
2. Combiner to CC.. current and distance
3. CC to batteries .. current and distance
4. Batteries to inverter.. current and distance
5. Inverter to appliances.. easy enough you're plugging into the inverter outlets.


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## MoonRiver (Sep 2, 2007)

I've just spent about 2 hours working on design. I have it about 1/2 done.

How does a bus bar work? Do I connect battery to it and then just connect all my positive wires from devices? What about negative wires? 

I'm also not sure about grounding for devices. Should I have a chassis ground for devices that also connects to negative post on battery?


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## Murby (May 24, 2016)

Bus bars are just basically big honking wire nuts.. although they look different, their function is the same. They are simply copper (don't use aluminum) bars that have holes drilled and tapped so that you can fasten multiple cable/wire ends to them and have electrical conduction between all cables. IE: a giant wire nut. 

Do not make the mistake of under sizing your busbar. I had though of flattening a 3/4 inch copper pipe and using it as a busbar for 2/0 cables.. but then I did a bit of math and discovered that would have been a bad idea. 

Your busbar must contain enough copper to carry the current load.. In other words, you have to figure out how much current it will carry and make sure the square area is large enough. This is no different than calculating the wire size needed to carry a specific amount of current.
You must also make sure your busbar is insulated from whatever you mount it to. This is where having fiberglass or PVC mounting blocks or stock comes in handy.




MoonRiver said:


> I'm also not sure about grounding for devices. Should I have a chassis ground for devices that also connects to negative post on battery?


At 12 volts it doesn't matter (one nice feature of low voltage systems), but be aware if you don't ground to the frame, you will need to provide circuit protection on both positive and negative sides. If you do ground to frame, then you only need it on the positive side.


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## MoonRiver (Sep 2, 2007)

Thanks. I had figured most of it out last night, but hadn't thought directly about size. Logically I knew I needed a big one, not a small one, but hadn't considered how big I needed.

What confused me about busbars was I couldn't tell if they acted as both positive and negative, or just positive or just negative. Then I found a schematic that made it clear. I'm thinking about using 2 - 1 negative and 1 positive.

Now that I know it is just positive or just negative, from a safety point of view it seems obvious.

I hope to finish my schematic today so you can comment on it.


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## Itinerant1 (Jul 23, 2018)

Here is an interesting thread about copper pipe for bussbar and resistance Murby probably understands it. I have seen copper pipe used as bussbars though. Although it goes over my head I'll guess they're correct on the results.¯\_(ツ)_/¯

http://forum.solar-electric.com/discussion/13285/busbar-as-battery-interconnects


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## MoonRiver (Sep 2, 2007)

Here's what I have so far. I guess at this point, I need feedback on any mistakes you find. I still need to size breakers, busbars, and make sure that 10 awg is large enough where I have it spec'd. I only ordered 20" of black and red each, so I won't have 2 spools of wire sitting around if I need to order some lower awg wire.

If I tie battery ground to chassis ground, what do I do with the separate grounding wire on some devices (inverter)?


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## Murby (May 24, 2016)

Why do you have a connection going from the positive busbar (10awg), through a breaker, through 12v fuse block, and then to the negative busbar? (its right in the middle of the drawing) All that's going to do is blow either the breaker or the fuse as soon as you connect it.

Everything else looks good.


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## MoonRiver (Sep 2, 2007)

I may have not used the right name for it. It's a fuse box for individual 12v circuits.


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## Murby (May 24, 2016)

Well that makes a lot more sense. Its a fused distribution panel.


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## Itinerant1 (Jul 23, 2018)

Its not in your diagram but your going to have the shunt coming off the neg battery between the neg bussbar? What size breakers are you using before inverter/ CC and pos bussbar. 
How many 12v items are you going to run from distribution panel? #10 seems small @ 30a but depends on the # items.


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## MoonRiver (Sep 2, 2007)

Itinerant1 said:


> Its not in your diagram but your going to have the shunt coming off the neg battery between the neg bussbar? What size breakers are you using before inverter/ CC and pos bussbar.
> How many 12v items are you going to run from distribution panel? #10 seems small @ 30a but depends on the # items.


If I'm understanding the shunt correctly, I put the shunt between the negative on battery and negative busbar, and the positive to either positive on a battery or positive busbar.

I haven't figured out size of breakers yet. That's all I have left to order. The 12v distribution panel is for the future. Since it is wired to busbars and not directly to battery, it will be easy to change out wiring if necessary. I also have some 4 awg wire if needed.


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## Itinerant1 (Jul 23, 2018)

If you look at the pic of my system it's basically what you drew. If your follow the wiring it goes to... 
NEG- shunt - power distribution post - inverter, CC, frame
POS- seleniods - power distribution post - inverter, 48v/ 120a breaker, 120a thermal breaker to 12v distribution panel.

Your CC 150/60 calls for a min 70a, max 80a


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## MoonRiver (Sep 2, 2007)

Itinerant1 said:


> If you look at the pic of my system it's basically what you drew. If your follow the wiring it goes to...
> NEG- shunt - power distribution post - inverter, CC, frame
> POS- seleniods - power distribution post - inverter, 48v/ 120a breaker, 120a thermal breaker to 12v distribution panel.
> 
> Your CC 150/60 calls for a min 70a, max 80a


Why is the shunt connected to the negative post rather than positive? Is it because electricity actually flows from negative to positive?


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## Itinerant1 (Jul 23, 2018)

Low resistance, plus that's how the install directions say to install it.


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## MoonRiver (Sep 2, 2007)

Here's an updated diagram. I added the shunt, specified amps for circuit breakers, and changed wire from positive and negative busbars to charge controller and distribution block to 4 awg.

I used a 70 amp circuit breaker between charge controller and positive busbar.
I used a 250 amp circuit breaker between 2000 w inverter and positive busbar.
I used a 120 amp circuit breaker between distribution block and positive busbar.


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## Murby (May 24, 2016)

120 amp breaker on a 4 ga wire is a good way to start a fire. 4 ga should be limited to around 70 amps depending on the insulation type, and really, if you think you might pull 70 amps through a 4 ga wire, you should be stepping up to something larger.
The 2/0 wire should have a 150 to 170 amp breaker.. 250 amps is far too high and will also start a fire.

I suggest you find a wire ampacity table and resize your wires and breakers.


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## Murby (May 24, 2016)

In your diagram, the only information that shut is going to provide is the battery current, in or out.. It won't show you what your charge controller is doing (although the controller might do that on its own), and it won't show you what the inverter is doing if the charge controller is sending juice to the batteries.


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## MoonRiver (Sep 2, 2007)

Murby said:


> In your diagram, the only information that shut is going to provide is the battery current, in or out.. It won't show you what your charge controller is doing (although the controller might do that on its own), and it won't show you what the inverter is doing if the charge controller is sending juice to the batteries.


How should it be wired then?


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## MoonRiver (Sep 2, 2007)

Murby said:


> 120 amp breaker on a 4 ga wire is a good way to start a fire. 4 ga should be limited to around 70 amps depending on the insulation type, and really, if you think you might pull 70 amps through a 4 ga wire, you should be stepping up to something larger.
> The 2/0 wire should have a 150 to 170 amp breaker.. 250 amps is far too high and will also start a fire.
> 
> I suggest you find a wire ampacity table and resize your wires and breakers.


I used this chart and this calculator to check wire gauge against amps. Today I used this calculator.

For inverter, I entered 12v, 12' (combined), 250a, 3% voltage drop, and all 3 say to use 1/0 wire.

For distribution block, I entered 12v, 12', 125a, 3% voltage drop, and all 3 say to use 4 awg wire.

I don't have a problem getting a lower amperage breaker or changing from 4 gauge to 2/0 wire, but I would like to understand why. Am I not understanding the calculators and charts or am I leaving something out? The distribution block is rated at 100a which is why I chose 120a for breaker.


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## Murby (May 24, 2016)

Your wiring is fine, the breakers protecting the wiring are too big.

Circuit breakers and fuses are not put in place to protect the components (inverter, lightbulbs, microwave oven, etc), they're there to protect the wires from over heating.

Your wiring sizing is great, no problems.. its the rating on the over-current protection is too big. You have a 2/0 wire that will need to carry about 160 amps to the inverter.. the 2/0 wire is rated for around 195 I believe.. but you have a 250 amp breaker protecting it.. so there's a 250 amp breaker that won't blow until probably around 260 amps, protecting a 2/0 wire that can only handle 195 amps.

Now, as far as your 3% voltage drop, its fine for grid power, but imagine this.. Lets say your inverter's low voltage cut off is set at 12 volts and your battery is currently at 12.5 and you put a large draw on it. Your 12.5 * 3% drop = 12.125 volts.. add in some resistance from the screwed connections and your inverter suddenly shuts off early on the large draw.

Not saying the 3% is dangerous or bad, its just not that great for solar setups as we need to squeeze every bit of power we can from our limited solar input. As it stands, your 2/0 wire will provide probably around a 1% drop so you're good there.. and I think you'll be fine with the 4ga wire on a 70amp(?) panel.

Change your breakers! Put a 175a breaker on the 2/0 wire and a 60a on the 4ga wire... Also, when it comes to the 2/0 wire, make sure your terminations are solid to the copper.. Don't go trying to install compression fittings with a shop vice.. just buy the correct tool or purchase the solder types and watch a few you tube video's on how its done. Making sure your terminations are perfect is important when dealing with high amperage stuff. You can screw around at 30 amps, but at 160 you need to pay attention to detail.


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## Murby (May 24, 2016)

MoonRiver said:


> How should it be wired then?


You're fine as it is, I was just pointing out that the shunt will only show what the batteries are doing. If you wanted more information than that, you'd need multiple shunts, as many systems have. 

Your inverter might have its own readouts, or not.. I'm pretty sure your charge controller will but you might want to check that.

There's no way to get a single shunt to tell you everything in such a system.. you'd need more than one.. probably three.


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## Itinerant1 (Jul 23, 2018)

According to the Victron data sheet for the BMV-712 it can read all.
"Download the Victron Bluetooth app Use a smartphone or other Bluetooth enabled device to
- customize settings,
- monitor all important data on single screen,
- view historical data, and to 
- update the software when new features become available."

"Other features 
- Battery voltage, current, power, ampere-hours consumed and state of charge
- Remaining time at the current rate of discharge
- Programmable visual and audible alarm
- Programmable relay, to turn off non critical loads or to run a generator when needed
- 500 Amp quick connect shunt and connection kit
- Shunt selection capability up to 10.000 Amps
- VE.Direct communication port
- Stores a wide range of historical events, which can be used to evaluate usage patterns and battery health
- Wide input voltage range: 6,5 – 70V
- High current measurement resolution: 10 mA (0,01A)
- Additional input to measure voltage (of a second battery), temperature or midpoint voltage, and corresponding alarm and relay settings"
Many RV'ers are using these with their smart phones.


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## MoonRiver (Sep 2, 2007)

Murby said:


> You're fine as it is, I was just pointing out that the shunt will only show what the batteries are doing. If you wanted more information than that, you'd need multiple shunts, as many systems have.
> 
> Your inverter might have its own readouts, or not.. I'm pretty sure your charge controller will but you might want to check that.
> 
> There's no way to get a single shunt to tell you everything in such a system.. you'd need more than one.. probably three.


OK. Got it for the shunt and for the circuit breakers.


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## Itinerant1 (Jul 23, 2018)

3% is very acceptable but less certainly doesn't hurt. With lead batteries yes the voltage loss can show it ugly head but with the Lifepo4 batteries he probably will not see that as an issue.

The other thing with lead batteries every once of produced power (eliminate as much voltage loss) is needed to get back to full battery where as his Lifepo4 will charge much faster and not sit for hours on end in an absorb stage trying to get to 100%.

If you would like I'll post a link to some #s on an excel sheet I put together over different periods of time at different SOC, current charging/ discharging, battery voltage & voltage from inverter what was drawing power. Showing the batteries down at 31% still using microwave, charging items (1,750w +) living day to day.

Using 1 shunt but the Magnum components interact with each other just like Victron can do.


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## Itinerant1 (Jul 23, 2018)

Murby you've peaked my interest with actual voltage lose with real world numbers off my system. Using the readings from my battery voltage to inverter voltage. I went through and added another column for voltage % drop while using misc appliances. This is off a 500ah LFP battery bank (5,120WH). Even at a lower SOC and high draw item the voltage is still pretty flat. 
The batteries have a monitor for voltage including individual cell voltage and the magnum me-arc has a display for both the inverter & CC.
https://drive.google.com/file/d/1QwTegENXkgQ-gIyrclTFsPPsBLfDZPfR/view?usp=drivesdk


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## Murby (May 24, 2016)

Itinerant1 said:


> Murby you've peaked my interest with actual voltage lose with real world numbers off my system. Using the readings from my battery voltage to inverter voltage. I went through and added another column for voltage % drop while using misc appliances. This is off a 500ah LFP battery bank (5,120WH). Even at a lower SOC and high draw item the voltage is still pretty flat.
> The batteries have a monitor for voltage including individual cell voltage and the magnum me-arc has a display for both the inverter & CC.
> https://drive.google.com/file/d/1QwTegENXkgQ-gIyrclTFsPPsBLfDZPfR/view?usp=drivesdk


Notice in your gray column, when you turn big loads on (Microwave, dehumidifier, and apparently your coffee pot), you're voltage drop goes up into the 2% to 3% range.. 

That's what I'm talking about.. Now imagine we just give you super conductors and instead, turn your 500ah battery into a 485ah battery, because its basically the same thing.

While your power losses are the same as they would be for lead acid, you do have one advantage and that is you won't notice them until the very end. The discharge curve for a lead acid battery is fairly uniform, it gets proportionally weaker as you discharge it. But the discharge curve for lithium batteries tends to be more flat.. that is, you don't notice it until the battery has run out of energy. 
Either way, the energy lost is the same, its just that while lead acid shows it gradually, the lithium just cuts out when its done.

There is no substitute for big copper and if you're going to run on it frequently, avoiding those losses will pay for itself in the energy you gain.. and its not like copper wears out.

I just picked up my busbars last night from my wire guy.. he pulled them out of a 3phase switching cabinet.. Plated copper, 1/4 inch thick by 2.5 inches wide.. and gave me a 3 foot piece to chop up as I see fit. Whoohoo! I paid $15 for it...

And a question for you... I want to see this coffee pot of yours.. What the hell man? What kind of coffee pot draws that much freaking juice? Come to think of it, I never measured my coffee pot....


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## Itinerant1 (Jul 23, 2018)

Mr. Coffee 12 cup.

Yes, using LFP there better be over/ under voltage protection. Besides the batteries having a bms the inverter is set for 12v never been lower than 12.4v @ 24% soc (120ah) using microwave.


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## MoonRiver (Sep 2, 2007)

Corrected amps for circuit breakers and added cable gland for roof entry. Still need to add PWM controller.


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## Murby (May 24, 2016)

You need a breaker on the battery terminals.
Notice in your drawing that the positive 2/0 wire is unprotected. You do have a 150a breaker and a 70a breaker protecting the inverter and mppt ctrlr, but imagine the inverter pulling 150 amps and a wire going to the mppt controller shorting out somewhere.. There's nothing to stop the current flow from burning the whole thing down.

You should add another 150 amp breaker where the battery on/off switch is at (just replace the on/off with the breaker), Remember, breakers protect the wires, not the components.
Your 150a + 70a breakers = 220 amps before anything pops..

Please note: I posted this and then edited it an hour later so re-read it again.


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## MoonRiver (Sep 2, 2007)

Murby said:


> You need a breaker on the battery terminals.
> Notice in your drawing that the positive 2/0 wire is unprotected. You do have a 150a breaker and a 70a breaker protecting the inverter and mppt ctrlr, but imagine the inverter pulling 150 amps and a wire going to the mppt controller shorting out somewhere.. There's nothing to stop the current flow from burning the whole thing down.
> 
> You should add another 150 amp breaker where the battery on/off switch is at (just replace the on/off with the breaker), Remember, breakers protect the wires, not the components.
> ...


Can I use a 200 amp breaker? When I run numbers through calculator, it show 2/0 for 12v - 200 amps - 14' @2%. Previously you suggested 170a breaker for inverter circuit, but I went with 150a because I could only find 150a and 200a on Amazon. 170a + 20a for distribution block= 190a, which is why I thought 200a might be better than 150a. 

At some point, I would like to add a 120 volt outlet on exterior of van, so that an extension cord can be plugged in. What I was thinking is a short cord that has a 3 prong plug on 1 end to plug in to inverter and the other end hardwired to the outlet. I want something like below pic, but I can't find it as an outlet, only inlet. Is it that because it needs GFI when using an outdoor outlet? Any ideas?


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## Murby (May 24, 2016)

You'll have to check your insulation type to determine if your 2/0 wire can handle 200 amps.. But if I was you, I'd stick to the 175 and if you can't find a breaker, use a fuse. 

Your external 120 volt connection needs to be a female, not a male.


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## MoonRiver (Sep 2, 2007)

Murby said:


> You'll have to check your insulation type to determine if your 2/0 wire can handle 200 amps.. But if I was you, I'd stick to the 175 and if you can't find a breaker, use a fuse.
> 
> Your external 120 volt connection needs to be a female, not a male.


That's why I was asking. Can't find a female plug (outlet) that is similar to male plug (inlet) I posted.


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## Murby (May 24, 2016)

MoonRiver said:


> That's why I was asking. Can't find a female plug (outlet) that is similar to male plug (inlet) I posted.


Keep looking... you can NOT use that plug as an outlet.. someone WILL get electrocuted and it will probably be a curious child who wants to know what's inside the neat little rubber cap.

Those kinds of plugs are made for what's called "Shore power".. they are inlets, meaning power flows from the grid into the RV and not from the RV out.


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## Bearfootfarm (Jul 13, 2006)

MoonRiver said:


> Can't find a female plug (outlet) that is similar to male plug (inlet) I posted.


The female plug would be on a drop cord.


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## Murby (May 24, 2016)

MoonRiver said:


> That's why I was asking. Can't find a female plug (outlet) that is similar to male plug (inlet) I posted.


https://www.ebay.com/itm/Leviton-IN...nt-Cover-5-15-15A-125V-5279-FWP-/391546215605

http://www.standardelectricsupply.c...Hubbell.Wiring.Devices,Electrical.receptacles










You might want to check wiring codes to make sure its even legal to install an outlet receptacle to an RV that way. And whatever you do, make sure its powered by a GFCI.


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## MoonRiver (Sep 2, 2007)

Thanks. I had looked on ebay and couldn't find it.

I had a thought last night that maybe it would be better to use the same type of utility door as on my rv. Just a locking door with a pass through cutout. That way I could plug directly into inverter.


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## Murby (May 24, 2016)

MoonRiver said:


> Thanks. I had looked on ebay and couldn't find it.
> 
> I had a thought last night that maybe it would be better to use the same type of utility door as on my rv. Just a locking door with a pass through cutout. That way I could plug directly into inverter.


That would be far better and doesn't run the chance of violating any codes.. Plus it has a nice locking mechanism.

I'm not familiar with the electrical codes for RV's but I can see the dangers of an external plug like that, and the fact that they are difficult to find tells me there is some code that prevents it.. otherwise everyone would be selling them.

I think your pass-through door is a much better idea.


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## Bearfootfarm (Jul 13, 2006)

Murby said:


> the fact that they are difficult to find tells me there is some code that prevents it..


Or what is much more likely is that no one typically runs power from the inside out.


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## MoonRiver (Sep 2, 2007)

Murby said:


> I think your pass-through door is a much better idea.


I'm using a 70a circuit breaker like this between the mppt controller and the positive busbar. Does it make any difference if the cable from the mppt controller connects to the top or bottom bolt in circuit breaker? I'm planning on connecting to top bolt, but just interested if it makes any difference. No instructions and I don't see anything online.


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## Murby (May 24, 2016)

MoonRiver said:


> I'm using a 70a circuit breaker like this between the mppt controller and the positive busbar. Does it make any difference if the cable from the mppt controller connects to the top or bottom bolt in circuit breaker? I'm planning on connecting to top bolt, but just interested if it makes any difference. No instructions and I don't see anything online.
> View attachment 68624


I've never known any breaker to NOT be bidirectional so my best guess is that it will be fine. 

You need to make sure you're not using a cheap China breaker.. make sure its UL listed and has all the appropriate certifications.. 

This is what I would use:
https://www.ebay.com/itm/EATON-HEIN...920964?hash=item33d6d9a944:g:wt8AAOSwIaFZJtgC
It's rated to 65 volts DC in case you ever upgrade to a higher voltage system... plus, notice on the bottom of it.. those little spade terminals in the middle are for alarms and signaling that tell you if it trips. 

Much higher quality breaker... I have some of these rated for 175 amps. They're large at about 7 inches long and made by Eaton..


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## Murby (May 24, 2016)

MoonRiver said:


> I'm using a 70a circuit breaker like this between the mppt controller and the positive busbar. Does it make any difference if the cable from the mppt controller connects to the top or bottom bolt in circuit breaker? I'm planning on connecting to top bolt, but just interested if it makes any difference. No instructions and I don't see anything online.
> View attachment 68624


I just took a look at your breaker online to get more information... I would definitely NOT use that in anything I owned.


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## MoonRiver (Sep 2, 2007)

Finally got the 2 300 watt solar panels installed on roof of van. I have some styrofoam taped on until I get them wired up.


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## Bearfootfarm (Jul 13, 2006)

I'd be thinking about an air dam across the front to reduce the flow under the panels so they don't generate lift.


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## Itinerant1 (Jul 23, 2018)

I would think unless the panels are hanging over the front windshield the air will flow over them, of course properly mounted/ secured to roof rack. Plenty of rvs with mounted panels not blowing off the roofs when properly mounted.


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## MoonRiver (Sep 2, 2007)

Itinerant1 said:


> I would think unless the panels are hanging over the front windshield the air will flow over them, of course properly mounted/ secured to roof rack. Plenty of rvs with mounted panels not blowing off the roofs when properly mounted.


Mounted with vhb tape.






ETA: I drove the van for the 1st time since mounting the panels. I checked before I left the house, after 1/4 mile, and then at the grocery store. Everything OK. 

On the way home, I hear a noise and look in rear view mirror and see a large rectangular object in the middle of the road. It took me a couple of seconds to realize the foam sheet taped to one of the solar panels had blown off. When I attached the feet to the solar panel, I had to cut some of the tape holding the foam sheet to the panel and had not retaped it.


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## Itinerant1 (Jul 23, 2018)

Many Airstream owners chose that so not to put holes in their aluminum. Seems to do well but like most things it's all in the preparations. 
The real test will be going down the highway at 65+ mph for a long period of time.


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## MoonRiver (Sep 2, 2007)

Itinerant1 said:


> Many Airstream owners chose that so not to put holes in their aluminum. Seems to do well but like most things it's all in the preparations.
> The real test will be going down the highway at 65+ mph for a long period of time.


I am going to take some parachute cord and tie 2 pairs of feet together. For example, the left rear foot on the front panel is only inches from the front left foot on the rear panel. My hope is that if a panel starts to come lose, the cord will hold the panel on the roof and make enough noise for me to hear there is a problem and pull over. Either that or it will tear both panels off at the same time!


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## MoonRiver (Sep 2, 2007)

I have an urgent question.

I am trying to finish up the install today and just realized I am short 2 2/0 gauge lugs. I have 4 cables left to make and only have 6 lugs.

Two cables are about 8" long and connect batteries - positive to positive and negative to negative.
One cable is about 18" long and goes from battery negative to shunt
One cable is about 18" long and goes from battery positive to on/off switch

I'm expecting the lugs on Thursday, but I want to connect everything today so I can get the batteries fully charged before any remnants of the hurricane get here. I have plenty of 2 gauge wire and lugs. Where would be the safest place to use a 2 gauge cable for a day or 2?

ETA: A work around is to just hook up 1 battery and then wire the 2nd one in when I get the lugs.


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## MoonRiver (Sep 2, 2007)

Everything is installed including the chassis grounds. The apps are working as well so I can check status of charge controller and batteries.

Gave it a real tryout today. I have to do some repairs that require electricity to my shed. Drove my van back near the shed and plugged in an extension cord. Ran several different saws fine.

Only problem was the ground was wet and my van got stuck! Waiting for roadside assistance to come pull it out.

ETA: I've made several trips that were about 150 miles roundtrip, mostly at 60-70 mph. The VHB tape made a tight bond so I'm not too worried about the solar panels coming off.


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## Bearfootfarm (Jul 13, 2006)

Now you need a winch 
Glad to hear it's all working well.


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