how do I use an off grid module?

[georgesuper]

OK, if anyone could help me with this I would really appreciate it.

Here is what I need, basically. I am going to hook up just 1 solar panel to my rv, and I need help figuring out how to do this. I know that the panel needs to be above 50 watts, at least 24 volts and at least 5 amps.

So if anyone could recommend a good module that would be great !

Also, along with the module I want to get a battery, so that would be nice to have to, and if anyone could recommend one I would love that!

But going further, do I need anything else besides the module and battery? do I need battery monitor? and what about a charge controller? any help would be great!

[mike95490]

You WILL need a charge controller, or risk boiling your battery dry after a couple days of un-regulated charging.

Do you just use the RV on weekends, or 7 days a week ? Lifestyle and future expansion of the solar system, will also determine your choices. Looking at the messages this week, you will need some sort of Low Voltage Disconnect, so if you leave a light or fridge on, you won't destroy your battery.

At first, stick with a name brand 'deep cycle marine' battery. You can add water to it after charging, and it's pretty forgiving of mistakes. When it dies, you can purchase a fancy $$ battery that will work a little bit better. (don't forget to reset the charge controller voltages for each type of battery.)

In an RV, look for a mount that will allow some air flow under the pane while parked, as the panels heat up, their output voltage drops, and you loose power.

If you can read a voltmeter, and have calculated your loads, I'd skip the battery monitor, which can cost more than the battery. As long as you can tell that you get to the float part of the charge cycle several times a week, you should be ok.

[georgesuper]

Thanks, I will only be using the solar panel to power my mobile dish, so that I can connect to the internet. I will probably be running it 7 days a week, and at night, which is why I want the battery. The thing is, I'm going to need a pretty heavy duty battery...

[Sage]

The first thing to do is to size your load. Does your dish operate on 120VAC or 12VDC?

If AC through an inverter, then buy a Kill-A-Watt meter for less than $30 and see how much power it draws.

If it operates on 12VDC, it's safe to hook an ammeter in the line to measure the current draw.

If you have a small inverter already, you might want to measure the DC current going into that in order to include DC-AC conversion losses.

After you get your load numbers, you can calculate panel size and battery size based on location, mounting, and temperatures.

[icarus]

My internet dish and router burn ~1.5 amp combined. (12vdc) The dish itself runs on a couple of weird voltages, regulated by the 120vac power supply, so you will need to invert. Assuming you are not charging the computer at the same time, you can do a calc. based on 1.5 amps. On the other hand, my Mac book draws ~5amps while charging and running.

Icarus

[Sage]

You MacBook draws five amps? Wow, more than I thought. I have an old G4 tower on the grid running 24/7. I plan to take it off grid and replace it with a MacBook or iMac. I measured a new iMac and found 50 watts AC with the machine running and the display off. What do you think your MacBook would draw if the display was off while running and the battery was fully charged?

Thanks

[georgesuper]

I kind of understand what you guys are talking about, remember, I'm just a begginer. What I really think would be best is if you guys could just tell me everything I need to get this dish running full time off grid. So, I know it takes at least 50 watts, 24 volts, and 5 amps, (although if I hook a computer up to it that will be more amps.) I want to be able to run the dish full time, including at night so I'll need a good battery that stores a lot of power. Anything else that you could recommend would be awesome! thank you guys, remember, I'm just a beginner...:( Oh, and also, money is no objective. Well, just dont make it TOO expensive If you need any more info ask me and I'll try to get it

[Windsun]

Why do you need a 24 volt panel?

[Sage]

I've been looking at a very similar thing. Out in sunny West Texas, I'm looking at maybe 6.5 kW/m2/day of insolation. I calculated a simple metric for my estimating. If I want to run 1 watt of load 24 hours, that is 24 watt hours (Wh) per day. If I have an overall system efficiency of 70 percent, then I need 5.3 watts of panel (24 / 0.7 / 6.5). If New York has an insolation of 4.5, then one would need 7.6 watts of panel per watt of constant load.

(Is this a reasonable way to estimate?)

A 50 watt constant up north would need 380 watts of panel. Panels might cost $1900 ($5 per watt), and the rest of hardware $1140 ($3 per watt?) for a total of $3040 without shipping, taxes, or install.

My point is that another 25 watts of constant load would add another $1520 in PV hardware. In my case, it will be cheaper to buy a new laptop then it will be to buy enough panel to power a free desktop computer.

[icarus]

You MacBook draws five amps? Wow, more than I thought. I have an old G4 tower on the grid running 24/7. I plan to take it off grid and replace it with a MacBook or iMac. I measured a new iMac and found 50 watts AC with the machine running and the display off. What do you think your MacBook would draw if the display was off while running and the battery was fully charged?

Thanks

Perhaps I should be more clear,,, It draws up to 60 watts, when the battery is almost dead, and I am doing something on the machine. I will do a Killawatt test later and post that information. I posted the 5 amps as a worse case "normal scenario".

With the display off, battery charged, if memory serves it draws ~1amp 12vdc. Sorry for any confusion,


Icarus