My hangout

harry

Hello all. I have enjoyed the postings here. I'm east of Waco, TX.

I have my hangout out in the the country that I use a few days a week. Kerosene lamps, battery lights, a LED TV off a marine battery which gives about 8/9 hours, 12VDC small water pump for showers. At most, I might add a small refrigerator in the future which may take more solar panels. I have the cabin wired as if it was connected to the grid. The TV is about 100 watt/hrs and roughly 1500 watts a day. Hope that makes sense.

I'm looking at some ideas on solar mostly for the TV and a light or two. Roughly, I'm looking at
2 - 140 Kyocera's and about 300 amps of batteries.

or something like this kit;

RV, Marine Kit With 315 Watts of DC Power and Morningstar 300 Watt Sine Wave Inverter
http://www.solar-electric.com/rvmakitwi315.html

Questions;
1. Is there an inexpensive way to get 12VDC from 24VDC battery bank?

2. As of now, the panels will be 35' to where the panel breaker box is. I was thinking about putting the batteries near the breaker box. What is a normal setup in feet between solar panels and batteries? Is 35' okay?

3. Any other thoughts.

thanks;
more questions to come.

Cariboocoot

Re: My hangout

Welcome to the forum Harry.

300 Amp hours of battery will be a challenge for 280 Watts of panel. Twice that would be good, but those two panels will only put out about 15 Amps max which is pretty low for that much battery (assuming a 12 Volt system).

There really is no inexpensive way to get 12 VDC from 24 VDC and keep the battery bank balanced, especially if the power requirements are high.

35' from panels to batteries is okay, providing you use the right size wire. However, with two 12 Volt panels in parallel running 15 Amps that whole distance and keeping the Voltage drop below 3% you end up with something like 4 AWG wire, which is pretty expensive.

That's why going up in panels (four for example) and running them in series/parallel for higher Voltage and then using an MPPT type controller the 35 feet becomes much easier to deal with.

1500 Watt hours per day is not difficult on a 12 Volt system. Your 300 Amp hours of battery would do this (if everything goes well) but your 280 Watts of panel couldn't supply it: 280 * 4 * 0.52 = 582 Watt hours.

Mostly I think you should get more panels.

harry

Re: My hangout

Thanks for the feedback. I'm getting some ideas and kind of roughing in something for what direction I should go. So for now I'll make my decisions around 12 VDC.

I was also looking at this 24 volt system with 45 amp MPPT.
RV, Marine Kit With 315 Watts of DC Power
http://www.solar-electric.com/rvmakitwi315.html
that steps down to 12 volt and then add 225 AH batteries to start with.
with a Morningstar 300 Watt Sine Wave Inverter.

Looks like I can have 2 panels (add one later) at 8 amps each for total of 16 amps, with #8 AWG for ~3% drop. (?)

Other thoughts is have the power setup at the panels and run UF to my shack's panel.

What I'm fuzzy on is how to match your batteries size to the panels?

Like I said, just getting some directions.

Appreciate your feedback.

Cariboocoot

Re: My hangout

It would be more accurate to say you match your panels to the batteries.

The capacity of the battery bank is determined by how much power you need to supply. For example your 300 Amp hours @ 12 Volts taken to 50% SOC is roughly 1800 Watt hours DC (150 Amp hours * 12 Volt nominal).

Once you've got that, then you need to recharge it. Most manufacturers recommend a minimum peak charge current of 5%, but that is net (no loads being used at the same time). If you go for 10% it will work in most cases. There is also an upper limit set by the particular batteries chosen. But with the 'generic' 300 Amp hours as an example: 30 Amps * 12 Volts = 360 Watts. However, panels won't put out their nameplate rating in Watts. But they will put out their Imp rating. So trying to get close to that 30 Amp number with 140 Watt panels that produce slightly more than 7 Amps calls for four panels: 4 * 7 = 28.

And then there is the MPPT advantage. If you were to calculate the array size using that type of controller instead of the PWM type you get: 30 * 12 = 360 / 0.77 (efficiency of array + controller) = 468 Watt array. This is because the MPPT can convert any 'extra' Voltage above charging set point to additional current.

These numbers, btw, work best with only 25% DOD. This has to do with how many Watt hours you can harvest in a typical day. If you use four of those panels for a 560 Watt array on a typical battery system you get a result like this: 560 Watts * 4 hours equivalent good sun * 0.52 over-all system efficiency = 1164 Watt hours AC.

Now compare that to 25% DOD on 300 Amp hours @ 12 Volts: 75 Amp hours * 12 Volts = 900 Watt hours. It's always good to have the panels capable of more power than the batteries, as they will (hopefully) be recharging the batteries and supply loads at the same time.

Which is where you get into the "when do you use the power" situation. Once the batteries are full the panels are capable of supplying more than they will from just maintaining Float Voltage. If you can use loads at that time (usually midday) then you can improve the over-all efficiency of the system.

Is it starting to make sense?

niel

Re: My hangout

ok i'll bite.
why do you need tv 15hrs a day? we do advise conservation.

harry

Re: My hangout

Cariboocoot;
Thanks for the detail info. Make more sense now. Somewhere along my solar journey I picked up some idea that "1 solar panel watt for 1 battery amp" was some rough figure. Appreciate the in-depth examples. I'll be back for more education lessons.


niel;
No, I'm not a couch potato. That figure is for worst case scenario when my old joints hurt. TV, lights and padded some for future items. For now, on the TV I usually spend couple hours in the morning and about 3 hours in the evening. Maybe I need to scale back that figure.

Thanks all;

zoneblue

Re: My hangout

I understand for small systems the allure of 12v. But sometimes small systems turn into bigger systems and then youre stuck with a 12v setup. To answer your question about how to get 12v out of 24v, that really is easy. 24v to 12v dc converters are readily availbel and not expensive. I recently bought a 15 amp unit for under $80. That way you can run 12v lighting , rv type appliances if you already have them.

One downside as mentioned in a thread three or four down is 24v inverters arent made in smaller wattages. Other than that wire size problems and over parallelling batterys etc all go away with higher voltages.

harry

Re: My hangout

Thanks for the input zoneblue. I'll look into that. Being my first venture in this and not pressed for time, I just getting some direction. Having 12 volt would be nice, I guess I could always replace those pumps with 110 volt as an outside thought. Just having it already there and hooked up sort of draws me to 12 volt.

Good info around here, so far I have no idea what "over paralleling" means. But hey, anything that does away with problems... I'm all for.

I can say the last few days have been real nice out at the cabin here in Texas. I'm really dreading summer.

Cariboocoot

Re: My hangout

Some basic info about choosing system Voltage: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power

"Over paralleling" is a reference to the problems of sharing current equally among multiple parallel batteries. The more parallel connections, the less likely all the batteries will have even current flow during discharge and charge.

harry

Re: My hangout

Cariboocoot, thanks for the time in explaining the above. Give me something to plug in some numbers with some understanding. zoneblue brought up an idea of using a 24->12 converter that should work fine. So... I'm now looking at some 24 volt system. As everyone else, don't want to waste a bunch of money.

So I'm looking at;
24v panels -> combiner box -> CC -> batteries -> inverter -> 110v panel box.

1. Should there be fuses?
2. What does a shunt do?

thanks;

westbranch

Re: My hangout

Harry, each one of those > would represent a fuse , the last one being in the 110 Distr panel. the size to be determined by the amperage at that point.

BB.

Re: My hangout

A shunt is a precision resistor with two heavy connections for your main DC cables, and two smaller connections for connection to a precision volt meter (remote amp meter, battery monitor, etc.).


-Bill

harry

Re: My hangout

Hi all.
Battery location question.

1. Inside, within feet of electrical panel box. Vented to the outside. Inside temperature > 90 deg in the summer when not occupied.

2. Outside on the deck, in the shade, in a vented box with CC and inverter, 20 feet from the electrical panel box. Temperature from about 20deg to 105deg.

What's your feedback on these locations?


ps: Ever tried to type with your pup in your lap?

westbranch

Re: My hangout

he he... guess you need to teach him the 'SIT' command... friendly critters though...

NorthGuy

Re: My hangout

If you want to install the battery box inside living quarters, consider that when they absorb and equalize they not only expell hydrogen, but they also smell very bad. Even if it's a sealed box vented to outside, you still need to open it for maintenance.

harry

Re: My hangout - SureSine-300

Hello all;
Thanks for all the advise you all have given so far.
I picked up some items from the host's site and have some questions about the MorningStar SureSine-300 inverter.

Image.
Attachment not found.

a. Manual states to use a GFI if installed in a RV. Since my cabin is like a RV without wheels and I use a GFI, how would I wire the earth ground wire to the GFI. The manual states that "The earth grounded leg defines the AC Neutral." Would the earth grounded wire be connected to one leg (neutral) and ALSO to the ground connection on the GFI? OR some other way?

otherwise

b. If connected to the panel box. In this case, It seems I would connect
Black -> PB Hot with jumper from one leg to the other as mentioned in this forum.
White -> PB Neutral.
and leave the PB ground unconnected?

c. I have the Midnite Big Baby Box fuse setup for SP,CC,Inverter. Do I still need the fuse on the AC side if connected to a PB?

One of the above is the way I will connect all this and the other question is for education.

Thanks. Advise is welcome.

Cariboocoot

Re: My hangout - SureSine-300

Personally I think GFCI is over-rated.

That aside, the output of the MS 300 is two AC wires, either of which can be "hot" making the other one "neutral" by tying it to Earth ground. The GFCI wiring would come after that point. Like in the picture they give but the "light bulb" would be the GFCI outlet.

Funny they want you to use it but can't be bothered to give a proper wiring diagram.

harry

Re: My hangout - SureSine-300

I thought the same. By their picture the GFI would have a hot and neutral but no ground which doesn't seem right. I don't know how it works and wonder if it would even work correctly without the ground.

Any thoughts on my b. and c. questions?

Cariboocoot

Re: My hangout - SureSine-300

That green wire in the diagram is the ground. As shown, it forms the N-G bond for the AC. At the same time the ground connection for the outlet would be connected to it.

If I have to draw this diagram I'm sending Morningstar a bill for professional services.

Cariboocoot

Re: My hangout

Frankly you don't need to fuse the output of a 300 Watt inverter at all; it will fault first (consider that the circuit wiring is designed for 15 Amps, not 3).