Taking the solar plunge

[stamar]

solar blvd has the 10 foot panels again for 100

http://www.solarblvd.com/Solar-Panels-&-Systems-Individual-Solar-Panels-55---95-Watt-(7)/c1_25_41/p933/Unisolar-PVL-68-68W,-12V-Thinfilm-Roof-Laminate/product_info.html

[douglitas]

lots of great info here.

we just got our 21' Sea Breeze and noted that the furnace load will pull down the storage battery after a night or two. So I picked up a 245 W 12V panel for $265.00 yesterday. We plan to set this on the ground in the sun while the home is parked in the shade.

On the subject of cooling...the idea of a fan blowing over ice is really related to the swamp cooler concept. you are adding humidity to the air which only works in dry climates.

of course you're familiar with propane powered absorption cooling. there used to be a company that made a propane fired A/C. the only elec power used was to run the fan. I've searched over the years for info on these units. They were called Arkla Servel.

here's a link to a report I just found..haven't read it yet but looks promising

https://docs.google.com/viewer?a=v&q=cache:z42RsLpw30UJ:www.propanecouncil.org/WorkArea/DownloadAsset.aspx%3Fid%3D3261+&hl=en&gl=us&pid=bl&srcid=ADGEESjxJEyTljWMSoSfWdtB8RSaIY11TCmYSoM-xEGJNFcf6MbWqSIkns7bycGSA-GtRv4oos9SlTRDkiwjoLcJ_UKIsZrB-inL2NuSBeJA4WbGToHotn_alcJY4EJE9QIcB_2Dt0hu&sig=AHIEtbQjicAcaV8z6jPjj7WmovNfTjO97Q

[Stevo]

I picked up a 245 W 12V panel for $265.00 yesterday.

Can you give us a link to the solar panel you bought please?

[douglitas]

http://inlandempire.craigslist.org/fod/3516866259.html

it's still up..don't know for how much longer. but the guy makes his living selling these so even if this ad is not reposted you ought to be able search LA craigslist for the terms and come up with the current ad.

[stamar]

solar blvd has one cheaper than that

http://www.solarblvd.com/p2567/Phono-Solar-230-Watt-24-Volt-Solar-Panel-PS230P%E2%80%9320/U/product_info.html

[Stevo]

And SolarBlvd.com also has a 240 watt panel for only $180.00. Thanks guys!

[douglitas]

solar blvd is 24v. What I wanted was 12v

[stamar]

I would say in short the advantage of a 24 volt panel is the lack of drop over the wiring.

The advantage of the 12volt panel is you can use a cheaper pwm solar controller and not have any power loss

For an rv setting with the 12 volt battery. Somewhere in this long behind thread is a youtube video showing the exact controller I got compared to a mppt controller and a 24 volt panel and it showed the output was like 25 percent more with the mppt.

So the cheaper controllers are better for single 12 volt panels. Or for 24 volt panels with 24 volt deep cycles.

Its a cost difference of at least 20 30 bux

[douglitas]

I have a 12 volt deep cycle battery. eventually I may want to expand the size of the battery bank. for now, I had to get the biggest battery that would fit in the little battery box on the Sea Breeze which is only 12.5" deep. even if you had a bigger bank and chose to combine batteries to make 24 volts, your DC appliances are wired for 12 volts. How you gonna step down the 24 volts? I guess it could be done. using a 12V system seems to be easier at this point.

[zero]

I have a 12 volt deep cycle battery. eventually I may want to expand the size of the battery bank. for now, I had to get the biggest battery that would fit in the little battery box on the Sea Breeze which is only 12.5" deep. even if you had a bigger bank and chose to combine batteries to make 24 volts, your DC appliances are wired for 12 volts. How you gonna step down the 24 volts? I guess it could be done. using a 12V system seems to be easier at this point.

Using 12 volts is a lot easier. You just have to keep wire runs relatively short to avoid using massive wire. Not an issue with an RV. I just wired a two story house with 12 volts DC. That was a challenge. The wire runs were too long to go upstairs so I installed a second breaker-panel upstairs that is fed by huge #2/0 battery cable. Even with that huge cable, with the 40 foot run and 60 amp panel there is still a 3.2% voltage drop at 60 amps.

If you had, let's say four 120 watt panels that had 20 feet of wire between them and the destination. You'd need #4 copper wire to keep the loss down to 2.4%. That's for just one pair of cables. If each panel had its own pair of wires, #10 AWG wire couild be used (2.4% drop), or #8 to get loss down to 1.5%.

Sticking with 12 volts makes it simple to use mainstream 12 volt applicances and devices. No limit to how many more 12 volt batteries you wire into the "bank" in parallel. Step-down tranformers to get 12 volts from 24 get very expensive and wasteful.

[Maineah]

I think a 24 volt system is just complicating your life a larger wire gauge would solve any voltage drop issue.

[stamar]

I have a 12 volt battery and. 24 volt panel there iis nothing complicqted about it at all.

The solar con troller automatically detects the batteryy used and lowers the voltage. This is with a seven dollar controller no less, all controllers for sale as new do that today.

the thought that you need a 24 volt battery is out of date....

Odds are your controller does that but maybe it doesn't what controller do you have? All of the ones I've looked at on ebay do that

An mppt controller is more efficiient in 24 volt 12 volt set ups.

[douglitas]

this is the controller I am planning on getting..looks like is works for 24V too though I don't see anything about it changing 24v to 12V.

http://www.amazon.com/Controller-Regulator-Charging-Automatic-Functions/dp/B008I0IZ7O/ref=sr_1_1?ie=UTF8&qid=1357720137&sr=8-1&keywords=AGPtek%C2%AE+30A+Solar+Panel+Power+Battery+Charge+Controller+%2F+Regulator+12V+%2F+24V+30+Amp+with+PWM+Type+of+Charging+%28Automatic+Lighting+Control+%2B+Time+Functions%29

[zero]

this is the controller I am planning on getting..looks like is works for 24V too though I don't see anything about it changing 24v to 12V.

http://www.amazon.co...Time Functions)

That's a good price for a 30 amp controller. Only thing I don't like is the company that sells it does not even list it in their database - so no manual available to read before you buy. Some controllers "autosense" input and output. If that is what it does - it can use a 24 volt panel for input and be hooked to a 12 volt battery or a 24 volt battery bank. It will sense which it is and adjust automatically. I assume that is what it does but I guess it's like Nancy Pelozi and Obama-care. You have to buy it first and then you get the manual and find out how it really works.

The big change in controllers when PWM technology came out is the input (from solar) does not have to be the same voltage as the output (to the batteries). I have one here that will take 12 to 200 volts from the solar input and put out 12, 24, or 48 volts to the battery bank. Mine is set with switches and not autosensing.

[stamar]

Ya all these questions are answered clearly here in this thread. There is a youtube video on it.

My seven dollar solar controller does it. For amature or below electronics questioning is it diifcult to change 24 volt input into 12 volt output no it is very simple.

Solar controllers in the past didn't include it because its available in a cheap little thing you can add....

Your contrpller is a pwm controller not ideal for switching voltage or multiple panels ideally it would be a mppt controller for that.

Id give yyou a cheap 20 amp mppt controller link but such a thing doesn't really exist. China is working on it still

Yyour controller does auto switch. Same as mine. The key here I'm asking about actually is that my 10 amp controller is 250 watts in 24 volt panels and 125 watts in 12 volt panel.... yet I think the switch is only goi g to handle 125 watts in 24 volt panels. That's because the output is more than 10 amps then.

It stands to reason but iit doesn't say. Its possible this one little controller is going to handle both of my panels at least for now but it seems unlikely