I have (x3) 150W panels, and need 1600Wh a day. Suggestions for battery banks?

[Fractalcathedral]

I apologize in advance, I've blown a cognitive fuse today and am still puzzled as to what the 3 vertical loops are representing in that diagram. Do the wires that they are marked through get put into conduit together?

As for the batteries, I had (x6) 12v, 155ah Vmaxtanks batteries fell in my lap, and I'm trying get some use out of them. That is the reason for the 12v box. So I was still hoping to use 4 of them in parallel/series.

Why is a lightning arrester useless on an RV? Even if my aluminum RV supposedly asks as a faraday cage, isn't it still possible for electricity to get sent through the the modules and damage my system / electrocute?

Why do you suggest fuses instead of circuit breakers? If one of the batteries malfunctioned, and I had to replace it, how would I shut off electricity coming to and from the batteries? Just make sure to disconnect the batteries from the battery fuse blocks (negative side first)?

[Johann]

Thanks alot, quite a lot of helpful information. I forgot to mention we intend to use it as a converted fridge, bought a Johnson Control device that you can adjust the temperature with. I assume we'll be keeping it around 40' degrees and opening it sparingly and for seconds at a time. The 471w/h a day estimate is its listed energy usage as a freezer. How much does that change the equation? Will the start up surge still require as much Amperage, but basically not be activated as frequently? Or will the amperage be reduced, with the run cycles remaining consistent?

As a freezer it would start less times and may even run less hours since the need to get something frozen out of the freezer is very small and will not happen often.

On the other side, a fridge will be opened more often and may cause the motor to start up more often and may even run the motor more often with a longer time even though the temperature as a fridge is set warmer.

It all depends on usage.

I have a standup freezer and the same size standup fridge and the freezer will use 1/2 amount of the energy. Because the freezer is opened up less than the fridge.

[Fractalcathedral]

It all depends on usage.

I have a standup freezer and the same size standup fridge and the freezer will use 1/2 amount of the energy. Because the freezer is opened up less than the fridge.

Thanks, that's good to keep in mind. I'll definitely be organizing it as well to avoid having to stand in front of it and search for what I want.

Okay, so the conduit guess was definitely not right, having more than a few tired brain cells I had to function on last night. I'm assuming it just means that the wires from terminal post to Inverter are both rated DLO 1/0, and the wires from charge controller to terminal post are both rated MTW #6?

Also does a 1,000 Watt 24v Inverter (large enough for anything I'll conceivably need), still qualify as a mobile inverter?

[inetdog]

I apologize in advance, I've blown a cognitive fuse today and am still puzzled as to what the 3 vertical loops are representing in that diagram. Do the wires that they are marked through get put into conduit together?

At a minimum they indicate that they should be run close to each other, rather than spatially separated as they are in the diagram. For some purposes such as minimizing electronic noise radiated from the wires, twisting the paired wires could be useful.
Depending on the type of wire and location within the vehicle you may need to use some sort of conduit, such as ENT (electrical PVC).

[Sunking]

I apologize in advance, I've blown a cognitive fuse today and am still puzzled as to what the 3 vertical loops are representing in that diagram. Do the wires that they are marked through get put into conduit together?

In this case means they are ran together and indicates both are Xxx AWG Wire like #10 AWG MTW between the panels and Controller

As for the batteries, I had (x6) 12v, 155ah Vmaxtanks batteries fell in my lap, and I'm trying get some use out of them. That is the reason for the 12v box. So I was still hoping to use 4 of them in parallel/series.

OK go for it.

Why is a lightning arrester useless on an RV? Even if my aluminum RV supposedly asks as a faraday cage, isn't it still possible for electricity to get sent through the the modules and damage my system / electrocute?

They are for Lightning and must be connected to EARTH to be functional. It is an RV. no Earth Connection, no safer place to be in a Lightning storm. Completely useless. Earth connections make electrical systems very dangerous. If a power line falls on your car, you stay inside where it is safe until authorities arrive and remove the line. If the line is hot, you open your car door, as soon as your first foot touches EARTH you are DEAD and will look like these two fine young men stealing copper.

solar3.jpg

Why do you suggest fuses instead of circuit breakers? If one of the batteries malfunctioned, and I had to replace it, how would I shut off electricity coming to and from the batteries? Just make sure to disconnect the batteries from the battery fuse blocks (negative side first)?

Try to find a dual circuit breaker that bolts to the battery Term Post. . If the Negative terminal is bonded as I have shown, it always stays connected. You open the positive line from the battery. In any bonded or grounded system, you never open the neutral circuit. Rally bad things can happen if you do and why electrical codes prohibit any switching devices on neutral conductors.

[Fractalcathedral]

I really appreciate it, Sunking and inetdog. I watched an 1.5 hour long video from Mike Holt at the NEC about grounding and electrical theory today. Very informative and fascinating, if anyone hasn't seen it, although I'm sure a 2nd or 3rd playback will reveal even more. : https://www.youtube.com/watch?v=mpgAVE4UwFw

My mind is blown, and I have a few questions.

When you ground the charge controller, the negative battery terminal post, and the Inverter, what happens to the electricity if there is a fault? It will all transfer to the same place, which is the chassis of the vehicle, correct? And the chassis is made of thick steel, which doesn't conduct electricity as well as other metals, and will have enough resistance to draw down the intensity of that current and diffuse it? And everytime electricity splits and finds different (parallel?) paths, it takes some of the voltage with it? Some of which may be diverted down to the ground and form a gradient down into the soil?

Can the green ground cords run together down to the chassis, or do they have to be connected to different parts of the chassis?

Does the ground wire allow current to travel back up it? Is there a risk of, lets say, driving over a live wire which makes a connection with the ground wire, travels into the system and fries your charge controller?

In Sunking's hypothetical powerline equation, is it a risk because I risk becoming a path between electrons as they travel to their source? The electrons want to close the circuit and will travel through whichever path is most conductive to get there?

Life becomes stranger and more bizarre everytime I look at it.

[Sunking]

I really appreciate it, Sunking and inetdog. I watched an 1.5 hour long video from Mike Holt at the NEC about grounding and electrical theory today. Very informative and fascinating, if anyone hasn't seen it, although I'm sure a 2nd or 3rd playback will reveal even more. : https://www.youtube.com/watch?v=mpgAVE4UwFw

I am a Moderator and former Instructor on Mike Holt Forum.

When you ground the charge controller, the negative battery terminal post, and the Inverter, what happens to the electricity if there is a fault?

The current flows through the vehicle steel back to the battery grounded polarity and operates the fuse or breaker. It provides a planned low resistance path to the source of power which in this case is the battery.

Let's say you pinched the battery positive cable between the battery positive terminal and inverter when you closed the metal cabinet door on it and cut through the insulation. All that current flows through the vehicle chassis right back to the Battery Negative terminal; and immediately operates the battery fuse adverting a fire.

the chassis is made of thick steel, which doesn't conduct electricity as well as other metals, and will have enough resistance to draw down the intensity of that current and diffuse it? And everytime electricity splits and finds different (parallel?) paths, it takes some of the voltage with it?

If wire were made out of steal instead of copper, then yes the resistance would be higher. But resistance is determined by how much cross sectional area the conductor has, along with the type of metal being used. A 6 AWG copper conductor has a cross-sectional area of only .02 square-inches. You vehicle chassis is massive of 100's of square feet. Parallel paths do not split or divide voltage, it splits current, and current takes all paths both known, unknown, planned, or unplanned. Bonding the battery negative terminal, Inverter and Controller chassis is a known, planned, path of sufficient capacity to safely carry fault currents.

Your vehicle chassis is a far superior conductor to any you will use.

Some of which may be diverted down to the ground and form a gradient down into the soil?

No current is ever diverted to earth, it is forbidden to use earth as a conductor because it is a very poor conductor for voltages less than 600 volts. In an RV there is no earth connection or any possible way for current to flow through ground in an RV. Only utilities can use earth as a conductor.

Can the green ground cords run together down to the chassis, or do they have to be connected to different parts of the chassis?

They are as short as possible, meaning inches. You just need to be sure to scrape the paint off the surface down to shinny metal, clean the surface, use No-Ox grease on mating surfaces, and External/Internal Tooth washer (aka Dragon Washers) to bite into the chassis and terminal lug. T

[Fractalcathedral]

The current flows through the vehicle steel back to the battery grounded polarity and operates the fuse or breaker. It provides a planned low resistance path to the source of power which in this case is the battery.

Okay, so what you're describing is an 'effective fault current path'? Which is similar to equipment grounding (to the chassis) to prevent any arcing, if lets say, lightning hit the ground outside, and it pushed rogue electrons into the RV, onto the metal components, inducing voltage. That electricity wants to return to the earth, and without an effective, low impedance, ground path, it may arc across, travelling through my propane tanks and/or cat to get to some metal component that takes it closer to the ground OR Is it "safe" until I or someone else steps off the bus, circumventing the rubber tires seperating my bus from the ground, providing it with a place to go?

Let's say you pinched the battery positive cable between the battery positive terminal and inverter when you closed the metal cabinet door on it and cut through the insulation. All that current flows through the vehicle chassis right back to the Battery Negative terminal; and immediately operates the battery fuse adverting a fire.

When you say chassis, do you mean the base frame, or the outer structural framework, or both? I understand that for a "ground" cord to work efficiently, it should be as short, direct, and with as few loops as possible. My RV is aluminum on the outside, plywood, and then aluminum on the inside. Can I drill through the wall and 'ground' the charge controller to the outside aluminum shell, or must I push it through the floor, onto the big load-bearing frames of the bus?

I've read the batteries and charge controller should be close to one another, although at this point I remember the rule and not the reason. So can both cables (or all 3, including inverter) travel together (a short distance) through the same hole, to the same single dragon washer washer holding it against some conductive part of the chassis, allowing it to disperse that current as it seeks the negative battery terminal, where it will travel back up (via another, or the same ground wire?) to meet with (and blow) either one of those fuses on the battery term post?

The current flows through the vehicle steel back to the battery grounded polarity and operates the fuse or breaker.

I think I may be confused. In your diagram, the positive battery terminal has the fuses, and the negative side is grounded to the chassis. I thought the negatively charged electrons travel from the negative side, but rides back to source via the positive side?

[Sunking]

Okay, so what you're describing is an 'effective fault current path'?

Correct a planned fault path of sufficient capacity to safely operate over current protection devices.

Which is similar to equipment grounding (to the chassis) to prevent any arcing, if lets say, lightning hit the ground outside, and it pushed rogue electrons into the RV, onto the metal components, inducing voltage. That electricity wants to return to the earth, and without an effective, low impedance, ground path, it may arc across, travelling through my propane tanks and/or cat to get to some metal component that takes it closer to the ground OR Is it "safe" until I or someone else steps off the bus, circumventing the rubber tires separating my bus from the ground, providing it with a place to go?

You are making things up now which is impossible. You ground a system to short out cable capacitance which break down insulation dielectric, minimize touch potential differences in the event of a line fault. But ground does not mean EARTH. The drawing I made you is a Grounded System but has nothing to do with earth. It just means you only have to add fuses or breakers to only one polarity instead of both. A Floating System is far safer than a Grounded System. Industry does not use Grounded Systems because they are too dangerous and prone to outages.

All power has to return to its source. Lightning source of Power is Dirt. If lightning were to say strike a tree next to your parked RV, nothing will happen to you other than maybe blow out your windows and ear drums from the concussion of the explosion. No current will flow through the EV as it is isolated for Earth, and not Grounded. Your RV is Floating and no safer place to be in a Lightning Storm. High winds is another story, Lightning is of no concern.

When you say chassis, do you mean the base frame, or the outer structural framework, or both?

I mean the structural Frame of the vehicle. If you look under the hood at the SLI BATTERY negative term post you will see a few cable on it. Look and follow where the largest one runs as it goes to one of two places of either the vehicle frame or the engine block. Either way is very heavy solid path for the starter current and th emain path to clear faults. You wil also likely see a smaller cable going to the firewall or other structural components that provide the nornal current return path for things like head lights, electronics, ect. If you use a large enough cable you can run all the ground conductors from the solar system to the negative post of the SLI battery. Some do that especially those who want to minimize electrical interference with th eTV radios and otther sensitive electronics.

I've read the batteries and charge controller should be close to one another, although at this point I remember the rule and not the reason. So can both cables (or all 3, including inverter) travel together (a short distance) through the same hole, to the same single dragon washer washer holding it against some conductive part of the chassis, allowing it to disperse that current as it seeks the negative battery terminal, where it will travel back up (via another, or the same ground wire?) to meet with (and blow) either one of those fuses on the battery term post?

That is how I would do it.

I think I may be confused. In your diagram, the positive battery terminal has the fuses, and the negative side is grounded to the chassis. I thought the negatively charged electrons travel from the negative side, but rides back to source via the positive side?

You are making stuff up again. Technically you can bond (ground) either the negative or positive battery terminal, the battery could care less and does not know. Which ever side is bonded is called neutral or return. Makes no difference. The ungrounded polarity is HOT and where the over current protection devices (OCPD) are installed on. If we FLOATED the system then you are required to install OCPD on both polarities as bot would be HOT. Doubles the cost but eliminates most outages and electrocution. But there is a catch. Equipment manufactures took it upon themselves that all 12 volt systems shall have the Negative terminal bonded to the chassis. Which means you must reference your battery negative terminal to th eframe. If you fail to do this means your expensive electronic will do it for you in a unplanned manner. So if there is a fault all that fault current travels through your expensive equipment which it is NOT designed to do and would let the magic smoke out.

Bottom line any current that leaves the battery has to return to the battery. No more or no less. Which way the current flows is irrelevant. Electron theory is negative to positive. Conventional current theory is positive to negative. What flavor do you like. Most use Conventional Current Flow because you work with positive numbers. Weirdos like scientist like to be different and use electron current flow because they like working with negative numbers. So pick your side of the theory.

All you have to know is Queer electrons blow fusses.

[Fractalcathedral]

I mean the structural Frame of the vehicle. If you look under the hood at the SLI BATTERY negative term post you will see a few cable on it. Look and follow where the largest one runs as it goes to one of two places of either the vehicle frame or the engine block. Either way is very heavy solid path for the starter current and th emain path to clear faults. You wil also likely see a smaller cable going to the firewall or other structural components that provide the nornal current return path for things like head lights, electronics, ect. If you use a large enough cable you can run all the ground conductors from the solar system to the negative post of the SLI battery. Some do that especially those who want to minimize electrical interference with th eTV radios and otther sensitive electronics.

Okay, first I want to say how much I appreciate your help on this. I want to understand every part of the thing I am to be living in and this is totally vital for me. I no longer want to be surrounded by systems that I don't understand, and I'm definitely not going to put wire no. 1 in (or let someone else do it) without knowing the precise reason why, and all the dangers associated with it.

As I understand it, when removing a car battery, one removes the negative connector first, because if the positive connector touches any part of the car's chassis (ground) it will complete the circuit, make sparks, and potentially electrocute you. In the wiring on your PV diagram, (being grounded to the chassis) if I removed the positive connection first, and then touched the chassis of the bus, would it do the same? Which side would you disconnect first in a floating system? Would it make a difference?

Technically you can bond (ground) either the negative or positive battery terminal, the battery could care less and does not know. Which ever side is bonded is called neutral or return. Makes no difference. The ungrounded polarity is HOT and where the over current protection devices (OCPD) are installed on. If we FLOATED the system then you are required to install OCPD on both polarities as both would be HOT. Doubles the cost but eliminates most outages and electrocution. But there is a catch. Equipment manufactures took it upon themselves that all 12 volt systems shall have the Negative terminal bonded to the chassis.

But since I'm going to have a (nominal) 48v coming from the panels and feeding into a 24v battery bank, can I just have breakers on both sides and cut out all the grounding? It would make it safer, but cost double? Wouldn't it just be the price of the terminal post and 2 MRB fuses? But wouldn't that increase the danger from touch potential differences on the wires acting like capacitors, in case of a line fault? Since I won't be grounded to Earth, (and it seems like alot of the danger of grounding is current coming up from the ground rod and destroying equipment), what dangers would being bonded to chassis increase? If I drove over a live wire, say, would the electricity potentially make a connection to the chassis / grounding cords and fry my equipment?

[inetdog]

Okay, first I want to say how much I appreciate your help on this. I want to understand every part of the thing I am to be living in and this is totally vital for me. I no longer want to be surrounded by systems that I don't understand, and I'm definitely not going to put wire no. 1 in (or let someone else do it) without knowing the precise reason why, and all the dangers associated with it.

As I understand it, when removing a car battery, one removes the negative connector first, because if the positive connector touches any part of the car's chassis (ground) it will complete the circuit, make sparks, and potentially electrocute you. In the wiring on your PV diagram, (being grounded to the chassis) if I removed the positive connection first, and then touched the chassis of the bus, would it do the same? Which side would you disconnect first in a floating system? Would it make a difference?



But since I'm going to have a (nominal) 48v coming from the panels and feeding into a 24v battery bank, can I just have breakers on both sides and cut out all the grounding? It would make it safer, but cost double? Wouldn't it just be the price of the terminal post and 2 MRB fuses? But wouldn't that increase the danger from touch potential differences on the wires acting like capacitors, in case of a line fault? Since I won't be grounded to Earth, (and it seems like alot of the danger of grounding is current coming up from the ground rod and destroying equipment), what dangers would being bonded to chassis increase? If I drove over a live wire, say, would the electricity potentially make a connection to the chassis / grounding cords and fry my equipment?

Where to start? Well, at the beginning.

Yes, that is the reason that you remove the negative terminal first. If the loose negative terminal touches anything except the battery post there will be no sparks since there will not be a complete circuit. There still may be a smaller spark when you remove the negative terminal because there may be load current flowing.
For that reason the suggestion when jumping a car battery is to make the negative jumper connection to frame metal rather than to either battery's negative post. Just in case there are flammable gases.

Capacitance does not mean much of anything in terms of energizing wires when you are looking at DC. That is an AC phenomenon.
Now if your 120V line happens to hit one of your battery wires without benefit of insulation, then you have a problem because the AC is grounded and so touching any part of the DC side of your system will now send current through you. Until then no fault current will flow and no overcurrent protection will be activated.

Current does not "come up from the ground" and destroy equipment.
If the ground is not very good and a high enough fault current flows, everything attached to that same ground may end up above earth ground and be a hazard. But that is why we bond the ground to the neutral, so that enough current will flow to trip the protector somewhere.

PS: Not all off-grid inverters will accept an ungrounded DC input, so read the specs carefully.

[Sunking]

As I understand it, when removing a car battery, one removes the negative connector first, because if the positive connector touches any part of the car's chassis (ground) it will complete the circuit, make sparks, and potentially electrocute you. In the wiring on your PV diagram, (being grounded to the chassis) if I removed the positive connection first, and then touched the chassis of the bus, would it do the same? Which side would you disconnect first in a floating system? Would it make a difference?

If you remove the wiring from the positive battery terminal first there is no chance shorting anything out because you opened the circuit path. You can drop that cable once removed and nothing will happen. The reason you remove the negative first is because it is not hot. If your wrench should touch the frame of the vehicle while working on the negative terminal nothing happens.

If the Negative is still connected, and you take off th epositive first you could have a problem. Not with electrocution, but fire. If you wrench slips and make contact with the vehicle frame and battery post, you got fire. I have seen a man have his wedding ring blown off his finger.

But since I'm going to have a (nominal) 48v coming from the panels and feeding into a 24v battery bank, can I just have breakers on both sides and cut out all the grounding? It would make it safer, but cost double? Wouldn't it just be the price of the terminal post and 2 MRB fuses? But wouldn't that increase the danger from touch potential differences on the wires acting like capacitors, in case of a line fault? Since I won't be grounded to Earth, (and it seems like alot of the danger of grounding is current coming up from the ground rod and destroying equipment), what dangers would being bonded to chassis increase? If I drove over a live wire, say, would the electricity potentially make a connection to the chassis / grounding cords and fry my equipment?

Sorry but most of that is nonsense. Current does not rise out of earth from a ground rod. The main purpose of a ground rod, is to give lightning a path to go to and keep it out of your house.

Cable capacitance is only a concern with high AC voltages.

If a system is Floated, there is no touch potential because nothing is referenced to ground. You can touch a 1000 volt line in a floating system and not receive any shock. You would have to touch one polarity with one hand, and the other polarity with the other hand to complete the circuit and receive a shock.

If you ground a system one polarity is referenced to ground, it is called Neutral. The other conductor is Hot and if it were 120 volts and you touched it, and you are grounded you get shocked because you become part of the circuit. So in a grounded system if a hot wire touched ground, fault current flows, and if designed correctly will operate the fuse.

In a Floating system no conductor is grounded. You have two hot conductors. If there is a ground fault, nothing happens and continues to work normally. In a Floating System you have to use a Ground Fault Detector. So if one of the Hot wires becomes faulted to ground sets off an alarm alerting the operators there is a ground fault. Once that happens maintenance personnel can then perform an ordely shut down with out interrupting operations/production and make necessary repairs. That is why Industry does not use grounded systems. They are prone to unnecessary interruption in power, and are a extreme shock hazard in high voltage operations.

In systems 50 volts and lower you have the option to either float or ground a system. You have no choice but to ground the system because your CC and Inverter have the battery negativ einput and chassis bonded together.

[Sunking]

If the ground is not very good and a high enough fault current flows, everything attached to that same ground may end up above earth ground and be a hazard. But that is why we bond the ground to the neutral, so that enough current will flow to trip the protector somewhere..

Not quite how it works Dave. If for example a nearby tree is struck, you will have ground rise potential. Assuming you have a proper single point ground all that happens is the ground rises together. There will not be any difference in potential inside the house. In order for current to flow, it must have a point to enter, and a point to exit to make a complete circuit. If you have a single point ground there is no way for current to flow.

Think of it like a 1000 volt battery setting in the garage with nothing connected, just sitting there on the floor. You can touch either polarity and nothing happens. Touch both to complete the circuit, and you are dead. The current goesinza the right hand, and goes outza the left hand cooking everything between them.

Now if lightning strikes your house, you got big problems as current is taking all paths heading to earth including your ground rod.

[Fractalcathedral]

Sorry but most of that is nonsense. Current does not rise out of earth from a ground rod. The main purpose of a ground rod, is to give lightning a path to go to and keep it out of your house.

It won't let me upload a picture right now, but in that Mike Holt video, there is a diagram showing lightning hitting a spot, travelling across the ground, travelling up a Generator's ground rod, going through a circuit box, which is then grounded, and another one damaging a CNC machine. I guess I misunderstood it.

[SunEagle]

It won't let me upload a picture right now, but in that Mike Holt video, there is a diagram showing lightning hitting a spot, travelling across the ground, travelling up a Generator's ground rod, going through a circuit box, which is then grounded, and another one damaging a CNS machine. I guess I misunderstood it.

Lighting will go wherever it wants to. My friend had his RV "shocked" when a bolt hit the ground close to where he had it stored. Because he had his hydraulic leveling pads extended the lighting was able to find a path up through them and into his electrical system. That bolt took out a number of things (tv, inverter/charger, including melting parts of one of the leveling pads and extension cylinder.

You have a chance if the lightning hits the top of your RV but when it comes up from the ground there isn't anything that will really stop it.