Small Solar System

Posted by Patrick Guenette on September 07, 2008, 12:48:54 PM

Hi Romeo,

Thanks. I went to see the diagrams in the gallery you posted, and I understand the principles behind them. I am not an electrician, so codes etc I have no knowledge of.

What I am concerned about is the potentially high loads I will be transferring from the batteries to the inverter. I bought a 3000w inverter because I am planning on using that much. And the inverter is a 12v DC to 110AC inverter. So does that mean if I'm drawing 3000w, the batteries will be supplying 250amps at 12v to the inverter? If so, how dangerous is this amount of current? And how thick of a wire do I need? Any special connector clips needed? (heavier gauge etc)

Also, my panels are supposed to be 15watt panels. (12v - 1 amp). But today, I decided to test one with a meter. When I hook it up, it shows 24.4v ?? Does this mean my panel is defective, putting out the wrong voltage? Just paranoid because I have no idea what will happen if I hook up the wrong voltage to my 12v 100ah deep cycle batteries. Could blow them up for all I know.

Thanks for your help

Posted by Tom Mayrand on September 07, 2008, 12:58:01 PM

Re: Small Solar System (Reply #6)

Patrick, those stores should have them. They may call them a junction box. Or just look for what I described, several smaller contacts connected to one large contact. Actually what you are dealing with isn't that big a deal. The ten small wires can be connected to a larger wire using copper wire clamps.
As far as current draw. At best, you are making 10 amps per hour. That's only 50+ amps a day. You can't expect to draw 500 W or 2500 W at 12 volts (40 - 200 amps) for any length of time before you drain your 100 amphour battery.

Posted by Patrick Guenette on September 07, 2008, 01:06:30 PM

Re: Small Solar System (Reply #7)

Thanks Tom. Yes I understand that I'm not generating a whole lot of power with these. But once all setup successfully, I intend to add more panels as time/money allow. My end goal is to be completely off grid. Based on my usage (looked at last 24 months), I'm using about 700khw per month and that includes my geothermal heat pump furnace. So a 5kw panel array should meet my needs for complete off grid.

Just starting small with this ~0.15kw system

Only need to make it 35 times bigger !! lol

Thanks again... I'll go back and ask for a junction box.

Patrick

Posted by Patrick Guenette on September 07, 2008, 10:31:17 PM

Re: Small Solar System (Reply #8)

Okay, got a junction box (was essentially just a metal box with holes in it) and got some of those twist things to twist and connect wires together. So think I have that solved.

Couple more questions - If I am ever using 3000w of electricity from the batteries to the inverter, at 12v, that's 250 amps! (I think?).... What gauge of wire do I need to support this?

The biggest wire I could find was a car battery wire (think it is 4 gauge?). - Would this suffice?

For the connections from the solar panels to the charge controller, I bought 20amp "heater" wire... is that ok? Same for the connection from the charge controller to the batteries.. I intend to use the 20amp "heater" wire (it's a red wire).

And last - To connect my two 12v deep cycle batteries in parallel, is the "battery cable" big enough? And is there any risk that I electrocute myself when connecting them? Any special order I need to follow? (example; connecting negative to negative first or the other way around?).

I know it is only 12v, but it's 100ah...isn't it the amps that are dangerous?

Thanks,
Patrick

« Last Edit: September 08, 2008, 12:40:38 AM by Patrick Guenette »

Posted by Patrick Guenette on September 08, 2008, 12:40:21 AM

Re: Small Solar System (Reply #9)

Sorry last question - I have a Franklin 3/4hp well pump, setup with a control box in my basement. The box says 230v. Anyone have any idea how many amps this pump needs?

Thinking I will need a 120v to 240v transformer hooked up to my 120v inverter to use it. But the inverter is only 3000w. So if I use a transformer to boost the 120v to 240v, that means it will only be able to pump out 12.5 amps @ 240v right?

Think the pump is on a 15amp breaker. - But hoping it would not use more than 12.5 amps @ 240v...anybody know?

Thanks,
Patrick

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