complete newbie question on 12v-110v-12v conversion

[Sunking]

Seems some of you or I have a problem understanding basic principles of a question.

So what was your question?

Or that some of you get into so fine grained details that you missed the starting question altogether.

What detail, you have not provided one detail. Just claims that are impossible and a crystal clear lack of undertanding how electricity really works. If you did understand you would have never selected 12 volts.

So here are two questions that will allow us to help you out:

• What make and model charge controller are you using?
• What Battery Amp Hour Capacity are you using at 12 volts?

[billvon]

Thanks for that. I confirm you're right. Laws of physics... Now to know how to cut the 110v cord to affix a 12v-> whatever voltage for my fridge.

Unless it's a Sunfrost (or other DC fridge) your refrigerator uses an AC compressor with an induction motor, which will not run on DC _or_ 12 volts.

I can afford to use 12v accross the board for if I install my 12v supply in the center of the house... I'll never run more then 20 feet. So power loss is minimal.

For many devices that will work - but you will likely always need an inverter for a few 120VAC appliances.

[inetdog]

Or that some of you get into so fine grained details that you missed the starting question altogether.

Is this the starting question:

The thing is that I find stupid to convert 12V to 110V for the fridge when itself has an transformer inside (I checked) to transform it into whatever voltage it needs.

Could someone nudge me in the right direction to tell me what it is called I am looking for? Can't I convert 12v directy to the "watever voltage" mentionned above?

If so, please provide more information about the fridge model you are talking about. Roughly 99% of the refrigerators made which run off 120 volts use that 120 volts without modification to run the compressor motor and maybe a fan motor or two, and a solenoid if there is a water dispenser or ice maker.
If there is a transformer in such a refrigerator, it will be there only to power the controls (either electronic or pure thermostats and timers.)

A refrigerator which is designed in a way that will let it run off 12 volts (or any other voltage) DC, will be several times more expensive than a 120 volt AC fridge.
Just as your statement about the tankless water heater led most of us to react as if you thought that the DC was supplying the heat instead of just running the pump, we are thinking that either there really is not a transformer in your fridge or else that it is only supplying power to a very small fraction of the parts inside.
Please give us a manufacturer and model number so we can better understand what your situation is.

My intention is not to be right (although I most often am) but to efficiently answer both your asked question and any questions that you should have asked but did not.

Last but not least, the fact that something works is a very positive thing, but if it works and will also keep working and cost the least amount of money possible that is even better.

[dukejustice]

Thanks to all of you.

Seems some of you or I have a problem understanding basic principles of a question.

As my container home is 90+% wired hand hooked, with almost a proper surface of panels already (missing 1.5kw of panels yet), a sufficient amount of batteries and I CAN CLEARLY SEE THAT EVERYTHING LIGHTS UP or heats up... I seem to detain some kind of proof that some of you are wrong.

Or that some of you get into so fine grained details that you missed the starting question altogether.

The house is made and liveable. I have a tendency to self determine that being right is too important for some of you.

Is that paying attention enough russ?

[inetdog]

With DC the losses are purely resistance. With AC you have resistance plus reactance losses.

Plus skin effect increases in the resistive losses, although these are relatively small at 60Hz until you get into very large conductors.

[russ]

Dukejustice - Sunking is spending time trying to explain where you are going wrong. It is obvious you know nothing about electricity except where the light switch is.

This 12 volt stuff is pure blather.

I really suggest you pay attention.

[Sunking]

I think his question is if most appliances have an ac-dc power supply inside, why aren't they all supplying an ability to run directly from dc, saving one from having to essentially go from DC > AC > DC (internally) and cut down on losses?

Sorry going to have to punch some holes in that theory.

First what voltage would that be? About the only thing in your house that has a 12 volt DC supply is your desktop computer, and that is only part of it as they also have a -12 volt rail. Now it becomes 24 volt.
What about that TV? Nope anywhere from 20 to 50 volts.
What about that stereo? Nope those can run up to 150 volts.
Got something with a motor? All of it made to run directly 120 VAC.

This is an intelligent question - and the best answer I can come up with is that it has to do with power distribution losses between AC and DC. Appliances are designed to run from AC for the most part because they are operated very far from the power station, and power losses from AC distribution are minimal compared to running from DC. They discovered this at the turn of the century - DC won't travel very far before cable losses become too severe to run anything.

Sorry but not even remotely correct. The first systems were DC. All of Manhattan Island NY was DC up until 2007 when Con Ed turned off Pearl Street Station. All the elevators, air conditioning, lighting, ect in all those high rise sky scrapers are DC. Most building owners had to either buy large DC rectifiers or replace their equipment with AC models.

Dc has less loss than AC. In fact today most all long distance transmission is bipolar High Voltage Direct Current. Look it up. With DC the losses are purely resistance. With AC you have resistance plus reactance losses.

In fact, running 12V dc around a remote cabin for example, is not usually recommended - 24v or higher, even though still dc, is recommended to cut down on power losses and allows you to use smaller gauge wire. But we're still talking about limited range. To go any appreciable distance, AC is used instead of DC, and only converted to dc inside the appliance.

Now you are getting warmer.

As was stated earlier 120 watts = 120 volts x 1 amp. 120 watts = 12 volts x 10 amps. Minimum wire gauge you can use in a house is #14 AWG copper, and is safe for both 1 amp or 10 amps. But what happens if that gizmo is say 50 feet 1-way from the battery? What happens?

Now what got the OP in trouble are these statements:

My calculations are all made. My DIY solar panels are under construction. Off-grid inverters are on their way. Solar charge controler are here already. ETC.

I have only 1 concern... Which I don't know how to ask about, less again how to search this forum for : converting the few applicances I need to 12V. I find very futile to produce 12V (rather ±18V in the panels), store it, convert it to 110V to feed the house wiring, then convert it back to something else (almost all appliances have a transformer inside because almost no applicance use 110v directly). So I have about everything I need directly in 12V. Coffeemaker, toaster oven, on demand tankless water heater etc...

Now you have been around here long enough to know he is blowing smoke. If he had done one single calculation he would have immediately realized it is almost impossible to do this at 12 volts, especially the Tankless Hot Water Heater. He would have also realized he would be making panels for the rest of his life, and need a second container home to just hold all the batteries.

[shockman]

So you are a dick too shockman?[/QUOTE]

Don't get me wrong duke! I just figured after the first reply's on this thread we were in for some entertainment

[Naptown]

.

This is an intelligent question - and the best answer I can come up with is that it has to do with power distribution losses between AC and DC. Appliances are designed to run from AC for the most part because they are operated very far from the power station, and power losses from AC distribution are minimal compared to running from DC. They discovered this at the turn of the century - DC won't travel very far before cable losses become too severe to run anything.

Actually that statement is not true. AC and DC losses are identical. Back in Tesla's day there was no way to convert low voltage DC to high voltage. and visa versa. AC could be easily done with a transformer.
The big problem with DC and low voltage DC in particular is the current needed to do the same work.
A 100W appliance operating at 100V draws 1 Amp
A100W appliance at 12V draws 8.3 amps
Since voltage drop over distance is a function of current (amps) this is why the higher amperage of the 12v will produce a larger voltage drop than the 100.
At the same current and distance (This is just an example) say the 100V system has a 2V drop in voltage. This is a 2% loss
a 2V drop in a 12V system is closer to 15% and will cause things to fry or not operate.

[dukejustice]

At least I *think* that is the intent of his question...

Spot-on!

This is an intelligent question - and the best answer I can come up with is that it has to do with power distribution losses between AC and DC. Appliances are designed to run from AC for the most part because they are operated very far from the power station, and power losses from AC distribution are minimal compared to running from DC. They discovered this at the turn of the century - DC won't travel very far before cable losses become too severe to run anything.

Thanks for that. I confirm you're right. Laws of physics... Now to know how to cut the 110v cord to affix a 12v-> whatever voltage for my fridge.

In fact, running 12V dc around a remote cabin for example, is not usually recommended - 24v or higher, even though still dc, is recommended to cut down on power losses and allows you to use smaller gauge wire. But we're still talking about limited range. To go any appreciable distance, AC is used instead of DC, and only converted to dc inside the appliance.

I can afford to use 12v accross the board for if I install my 12v supply in the center of the house... I'll never run more then 20 feet. So power loss is minimal.

Dukejustice - don't cancel your subscription. Just develop a thicker skin for the online world that lacks gestures, body language, and whatnot.

I am moving inside a container house because I am tired to deal with dicks.

If dukejustice comes back on here I'm going to wip up a batch of popcorn! :>)

So you are a dick too shockman?

[PNjunction]

I think his question is if most appliances have an ac-dc power supply inside, why aren't they all supplying an ability to run directly from dc, saving one from having to essentially go from DC > AC > DC (internally) and cut down on losses?

At least I *think* that is the intent of his question...

This is an intelligent question - and the best answer I can come up with is that it has to do with power distribution losses between AC and DC. Appliances are designed to run from AC for the most part because they are operated very far from the power station, and power losses from AC distribution are minimal compared to running from DC. They discovered this at the turn of the century - DC won't travel very far before cable losses become too severe to run anything.

In fact, running 12V dc around a remote cabin for example, is not usually recommended - 24v or higher, even though still dc, is recommended to cut down on power losses and allows you to use smaller gauge wire. But we're still talking about limited range. To go any appreciable distance, AC is used instead of DC, and only converted to dc inside the appliance.

So maybe this answered your question a bit. Dukejustice - don't cancel your subscription. Just develop a thicker skin for the online world that lacks gestures, body language, and whatnot.

[shockman]

If dukejustice comes back on here I'm going to wip up a batch of popcorn! :>)

[russ]

Wow! I wasn't expecting that warm welcome. I am sorry to see that you have over 7500 posts. With that filthy attitude. I am surprised you lasted that long.

Look at this link and you'll see that it's not connected to the grid and that my affirmation wasn't totally wrong as the pump is 12V.

I am sorry for ever coming here to seek knowledge from people who know more then I.

THE REASON EXACTLY WHY I WANT TO CUT MYSELF FROM SOCEITY.

ADMIN: please freeze this account for I will not use it again.

It is strongly suggested you stay far away from electricity - you could well kill someone.

[Naptown]

You are an idiot and deserve to be cut off. 12 volt tankless water heater my butt. Farts can make more heat then a DD battery.

The 2 d batteries are for ingition only. the heat is from propane

[inetdog]

Look at this link and you'll see that it's not connected to the grid and that my affirmation wasn't totally wrong as the pump is 12V.

The heater is indeed a 12 volt pump driven heater, and the IGNITION is via D cell batteries. The water is heated by propane, not electrically. Your original post looked as if you were referring to electric heating.

The ignition is with 2 "D" cell batteries so it makes it great for off grid or other areas where electricity is not readily available.