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

[Sunking]

Isn't a car battery grounded, on the negative line? And that becomes 'neutral', but you can open it? And in fact should, first, always? What is different?

I am getting a little tired of explaining this. For current to flow, there must be a complete circuit. In a car, truck, whatever at 12 volts the systems are Bonded and Referenced to the vehicle frame. That makes the whole vehicle the batteries NEGATIVE TERMINAL.

In a fault, the ungrounded circuit conductor (positive) comes in contact with the vehicle chassis is the same as connecting it to the NEGATIVE BATTERY TERMINAL. When that happens you have a huge amount of current flowing of several hundred amps which should operate the OCPD like a fuse. That is called a SHORT CIRCUIT. The Short Circuit is complete by a dead fault connection of the positive and negative terminals of the battery.

The reason it is recommended to disconnect the negative first is in the event you are disconnecting the positive terminal and your wrench slips and makes contact wit the frame of the vehicle completing a SHORT CIRCUIT. Remove th enegative terminal and there is no circuit. The system is no longer BONDED aka Grounded.

What got this started is at some point you asked about putting a Disconnect Switch on the Negative circuit which is a NO-NO in a Grounded System. You can certainly disconnect the Negative Terminal on the battery for maintenance. Just make damn sure you remove all cable connected to the battery negative terminal.

[Fractalcathedral]

There's one thing I'm still not sure I understand. It sort of orbits around these statements.

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.

and...

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.

Is the bolded statement a contradiction? I can't tell if there's something I'm missing.

And this:

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.

Isn't a car battery grounded, on the negative line? And that becomes 'neutral', but you can open it? And in fact should, first, always? What is different?

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.

So if I have a grounded system as you've diagrammed, I should never open the 'neutral' or negative circuit, because it's bonded to the chassis. (What if you were to disassemble the entire thing? Would the negative terminal be safe to disassemble after the positive battery term post is detached?) So I take off the HOT battery post, with insulated tools, careful not to touch anything with exposed skin. And I finally take it off, and if I don't want to trip the fuse, so I let it rest on a rubber mat until I intend to put it back on? Put it on again with equal care so I don't become part of the circuit?

I know it's relatively low voltage, but my sister was electrocuted to death when I was young and the experience definitely instilled a healthy respect for electricity.

[Fractalcathedral]

This is for an RV right? Stick with 12 volts.

Well I've got the 12v batteries I am trying to find use for, so the alternative to 12v system is 4 in parallel/series. Which seems better because of the freezer's compressor start-up surge and conversion losses from 12v to 110AC.

[Sunking]

Awesome. I called the company a couple hours ago, and they OK'd it as well, along with saying:

"This should be fine as long as you do not exceed the 300 amp maximum for the fuse holder. I also would not stack more than two and make sure the highest loads are closest to the bottom."

You should never run more than 100 amps on battery.

Apparently it can connect the 12v car battery to the 24v bank, charging @ 14-10Amps. 240-336 Watts an hour is not especially impressive, but it seems to require a more niche product that inputs 12v and converts it to 24v. Maybe I'll find a better deal somewhere.

This is for an RV right? Stick with 12 volts.

[Fractalcathedral]

That will work.

Awesome. I called the company a couple hours ago, and they OK'd it as well, along with saying:

"This should be fine as long as you do not exceed the 300 amp maximum for the fuse holder. I also would not stack more than two and make sure the highest loads are closest to the bottom."

For battery isolator I am looking at the Sterling Power Procharge Battery-to-battery charger: http://www.defender.com/product.jsp?...772&id=2086430 in mind.

Apparently it can connect the 12v car battery to the 24v bank, charging @ 14-10Amps. 240-336 Watts an hour is not especially impressive, but it seems to require a more niche product that inputs 12v and converts it to 24v. Maybe I'll find a better deal somewhere.

[Sunking]

Apparently BlueSeas only has those 2-Output Battery Fuse Blocks, so I redrew my added to my diagram to show what I am thinking about using 2 of them on top of each other. Has anyone done this?

[ATTACH=CONFIG]6363[/ATTACH]

That will work.

[Fractalcathedral]

Apparently BlueSeas only has those 2-Output Battery Fuse Blocks, so I redrew my added to my diagram to show what I am thinking about using 2 of them on top of each other. Has anyone done this?

Battery Wiring Diagram.JPG

[Fractalcathedral]

Sunking, in reference to your diagram. I am trying to figure out how the actual cables will look like when attached, and how best to wire it into parallel/series.

Battery Bank Wiring.JPG

Would the positive Battery Fuse Block have 3 Inputs, instead of the 2 that were in the Blue Seas battery fuse blocks? Would the negative take-off terminal in the left corner have 4? (one for the ground cable) or can you ever double up and put multiple cables between the same screws?

Would the wire sizes remain the same (MTW #6 from controller to battery bank, and DLO 1/0 from battery bank to inverter)? What size cables do you suggest I use to wire the batteries together?

[Sunking]

Aha! That all makes sense now. That appears to be the same premise which makes multiple ground rods a bad idea.

No multiple ground rods is not necessarily a bad thing. If they are all bonded together to form a Ground Electrode system is a good thing. You just only connect to it once for you house. That connection is done outside at your service disconnect at you meter.

[Fractalcathedral]

The distance between you two feet can reach up into the of thousands of volts and kill you.

Aha! That all makes sense now. That appears to be the same premise which makes multiple ground rods a bad idea.

[Sunking]

Well I haven't ordered the Charge Controller or Inverter yet. The only things I have at the moment are modules and batteries. Is there some charge controller / inverter I could buy that would allow the system to be floating?

There are none I know of. Again not something you need to worry about. You are operating low voltage, not high voltage. Relax. The only dangerous item capable of starting a fire is the batteries from dead bolt faults. That is why you install the OCPD right on the battery post. The Inverter cannot produce enough current to even trip a circuit breaker let alone over heat a wire.

Does it matter that 4 of the panels, in series, are nominally 48v, but (according to their customer service), actually closer to 73vdc?

It may or may not as it depends on the Voc input of the Controller, and the total Voc of the 4 panels in series. A good CC will have a Voc input of 150 volts. Look at the panels Voc rating and if all 4 in series are 120 volts or less you are good to go. Otherwise wire them 2 x 2. If those are Battery panels th eVoc should be around 22 volts each and for in series is roughly 88 volts well under the limit of a 150 Voc controller.

[Sunking]

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 is called Step Gradient Potential, and happens when you have two of more contacts with earth, as in the case of the steel leveling pads.

Utility workers and have been killed by it. It can be induced from either utility high voltage or lightning. It lightning were to strike a nearby tree or object the current flows out along the earth. As that high current flows through earth the rather high resistance of dirt causes a gradient voltage difference of potential along its path. The distance between you two feet can reach up into the of thousands of volts and kill you. Been a few incidents during picnics where the shelter or tree was struck and someone holding a baby was killed, but the baby is not injured.

Morrow of the story put your feet together during a lightning storm and only use single point ground. Again for current to flow it has to have a goinza point and goes outza point.

If you look close at electrical sub stations you will notice steel platforms in front of equipment cabinets for workers to stand on. They are there specifically to eliminate gradient step potential in the even a fault should happen during switching operations.

[Fractalcathedral]

(From https://www.youtube.com/watch?v=YuDqXFvRv94 at 7:49)

Dangerous Ground

Direct lightning strikes on a person are rare. A lot more injuries are caused by the side-effects of a nearby strike.

If you are standing, say, at a bus stop, chances are that lightning will strike a taller object nearby like a tree or a light pole.

Immense power will be channelled downards into the ground and you will be injured (or even killed) if different parts of your body are touching the ground. This is due to the "voltage difference" effect.

How does that happen?

The voltage of electrical power from lightning decreases the further away you are from the strike point.

For instance, when a bolt hits a light pole, the voltage 5m away can be a sizzling 500,000 volts. At 19m and 20m from the pole, the voltage can be as intense as 200,000 and 190,000 Volts respectively, explains Prof Llew Ah Choy of the National University of Singapore.

So if a person is at that bus stop, with his left leg at 19m and right leg at 20m distance, he will be injured because the voltage difference is a massive 10,000 Volts. Electricity will flow up the left leg and down the right, causing shock and burns, especially to the lower part of the body."

So, how is that not electricity coming up from the ground through the voltage gradient caused by lightning strike?

I do see now that the original diagram I had drew the conclusion about grounding rods on was actually in regards to having more than one ground rod (or 'Auxiliary Grounding Electrodes') which gives the electricity in/on the Earth a path to ground, via coming up one ground rod and down the secondary ground rod.

[Fractalcathedral]

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.

&

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

Well I haven't ordered the Charge Controller or Inverter yet. The only things I have at the moment are modules and batteries. Is there some charge controller / inverter I could buy that would allow the system to be floating? One with 'Floating neutral' listed in description, perhaps? Would the charge controller be listed like that as well?

Does it matter that 4 of the panels, in series, are nominally 48v, but (according to their customer service), actually closer to 73vdc?

[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.