Solar Set up

[byrdz1]

I would really appriciate any thoughts on this set up. What I want to do is make sure I have a topped up battery all the time, I may need a cpap in the near future and I would like to be ready, my rig has both 12V and 110 already, now I need to keep the battery full so I can use it
Grape Solar 100W PanelCostco
http://www.costco.com/Browse/Product.as ... opnav=&s=1
• 100 Watt, 18.5 Vmpp, 5.42 Impp
• 900mm leads with Male and Female MC4 Connectors
• Panel Dimensions: 47.0” tall x 21.1” wide x 1.57” thick

Solar Power ControllerAmazon
http://www.amazon.com/HQRP-Controller-D ... controller
• HQRP® Solar Charge Controller plus HQRP® UV Chain / UV Radiation Health Tester;
• Equalisationvoltage: 14.8 Volt; High voltage disconnect: 14.4; Float voltage: 13.6Volt;
• Low voltage disconnect: 11.1 Volt; Low voltage reconnect: 12.6 Volt; Self-consumption: 6mA maximum;

InverterCostco
http://www.costco.com/Browse/Product.as ... opnav=&s=1
PowerBright 1500 Watt 12 Volt
• Modified Sine Wave
• Continued Power 1500W
• Peak Load Power Rate < 3000W
• Overload Output Power 1560-1400W
• No Load Current Draw < 0.4A
• Input DC Voltage Range 10-15.5V
• Output Voltage Range 117 +/- 10%
• Output Frequency Range 60 +/- 3Hz
• Max Power Efficiency > 90%
• High Voltage Cut Off Level 15.5 +/- 1V
• Low Voltage Alarm Level 11+/- 0.5V
• Low Voltage Cut Off Level 10 +/- 0.5V
• Short Protect Yes
• Overload Protect Yes
• ISO 9001 certified and ROHS compliant
• Standard Test Voltage Input DC 12V

Cables and so onBattery Tender Deltran Cigarette Lighter Adapter 081-0069-5 (So I can “back charge” through the 12V connection)
http://www.amazon.com/Battery-Tender-De ... sim_auto_5
Battery Tender 021-0123 Battery Tender Junior 12V Battery Charger
http://www.amazon.com/Battery-Tender-02 ... uto_text_b
Battery Tender 081-0069-6 Ring Terminal Harness with Black Fused 2-Pin Quick Disconnect Plug
http://www.amazon.com/Battery-Tender-08 ... auto_img_c

thanks in advance!

[Shadow Catcher]

There are a number of factors involved here.
Conservation is the first and most important, use of LED lights computer case fans in place of a Fantastic fan etc.
The second factor is to monitor battery state of charge I use a Victron battery monitor which has a a shunt that measures the power going into and coming out of the battery, there are others.
In all likelihood the CPAP machine you buy (should it be necessary) will run on DC. This is more efficient than using an inverter.

We just got back from a month long trip and seven days were off grid, we never got below 75% state of charge. Three days were in Big Basin Redwoods state park and we had almost no direct sunlight (those trees are TALL). This worked for us because I made a mistake when I bought our 180W panel I bought one made for a grid tie system and puts out better than 40V (I have seen it at 57V) which required an MPPT converter but means it will produce some usable current even in deep shade.

I looked at the HQRP controller, and bought a Morningstar arguably one of the best. One source for information in great detail, http://handybobsolar.wordpress.com

[bdosborn]

The panel is a good deal, its probably bigger than you'll need but the price is right. I looked at the specs and its a good panel for charging a 12V system.

The controller is sketchy, spend a few more bucks and get a Morningstar.
Sunsaver 10

The inverter is so-so. Do you really need such a big inverter? Inverters are more efficient when they're sized close to the load.

This site had better pricing on inverters the last time I checked :
Inverters

Bruce
P.S. I think most CPAP machines don't recommend running on a MSW inverter...

[S. Heisley]

There are battery-powered CPAPs (AC/DC) available; so, you may not need an inverter at all.

[byrdz1]

Thanks for the links and suggestions.

The inverter is for my bed. I have a sleep number bed in the trailer. (bought it from Craigslist) They are perfect for our application as they are very light, all of it zips off and can go in the washer (no fear of bed bugs), and they hold air like crazy (think months). Really they are a just a well built air mattress, but it is comfortable as heck. I don't know what the draw is, but what happens is I go out and find out that the bed is to hard and want to let some air out (after letting the air out to change the sheets). Then I am stuck. I don't need it for anything else, I just want to run the bed if I need too as sleeping is very important to me. I was hoping that the inverter was so big it would get the job done.

[bdosborn]

Hey, a guys gotta be comfortable, that's why we don't sleep on the ground anymore. I'll do some digging and see if I can't find the sleep bed electrical specs...
Bruce

[48Rob]

Can't you just use a "D" battery powered air bed inflator?

It would solve all the issues of having an inverter.

Rob

[eamarquardt]

I think that Shadowcatcher's input on the output voltage of the panels is important. As he states, two smaller panels in series will produce usable voltage when conditions are less than optimum. A single "12 volt" panel will not. Using higher voltages will also minimize the voltage loss, if other than short cables are used to connect the solar panels to the charge controller. The higher the voltage the less current that is required to transmit the same amount of power (watts) and as the voltage drop is proportional to the square of the resistance in a circuit it can become a factor in the efficiency of your system.

Sorry, Tex, no simple way to put it. It will work but it won't be optimized for less than optimal conditions.

You could always buy two and still use the small Morningstar MPPT controller. An MPPT controller would, though, be required to take advantage of the higher voltage produced by the panels in series.

Cheers,

Gus

[eamarquardt]

If all you want AC power for is to run a device to inflate your air mattress, you could use one of these:

http://www.amazon.com/Coleman-200000107 ... B0009PUQEG

Cheers,

Gus

[bdosborn]

Sorry, Tex, no simple way to put it. It will work but it won't be optimized for less than optimal conditions.

Hmm, this brings a few questions to mind:

What are the less than optimal conditions? How large of a gain in harvest will the "optimized" approach yield? And since when is voltage drop proportional to the square of the resistance, did they change Ohm's law when I wasn't looking?

What alternatives do recommend that will yield a higher solar harvest and what is $/watt?

Bruce

[bdosborn]

Can't you just use a "D" battery powered air bed inflator?

Rob,

The sleep number bed has an integral inflator that regulates the mattress firmness.

Sleep Bed Linky

I've poked around their site a little but can't find any electrical load info.

Bruce

[bdosborn]

Okay, after way too much time on the internet the only thing I found was an obscure reference that its a 1 amp motor in the sleep number bed blower. That's a 120 watts; figure 5 times that load for motor start up and a 600 watt inverter should do it. A smaller inverter (say 400w continuous/ 800 watt peak) will *probably* work but YMMV as motors draw more current on a MSW inverter. I would only use the inverter to tweak the bed pressure and then turn it off to avoid the no-load inverter draw on the battery. The sleep number bed is supposed to stay inflated when the power is off.

Bruce

[eamarquardt]

Sorry, Tex, no simple way to put it. It will work but it won't be optimized for less than optimal conditions.

Hmm, this brings a few questions to mind:

What are the less than optimal conditions? When the panels are in the shade. See Shadowcatcher's post. How large of a gain in harvest will the "optimized" approach yield? Apparently enough to keep Shadowcatcher's batteries at 75% charge. See his post. And since when is voltage drop proportional to the square of the resistance, did they change Ohm's law when I wasn't looking? Geeze, nobody's perfect. Note the time of the post. Why was I up? Because I was in pain (as I virtually always am) that most folks can't begin to imagine. I was thinking of power=I(squared)R. Opps. At least I wasn't thinking PV=NRT or D=1/2AT(squared), °C x 9/5 + 32 = °F, or something totally irrelevant.

What alternatives do recommend that will yield a higher solar harvest and what is $/watt? I think Shadowcatcher pointed out the advantages of a MPPT charge controller and panels in series. This combination of panels and controller will charge a battery when a single panel or panels in parallel won't as in when the light isn't as bright due to clouds, shade, solar eclipse, or nuclear winter. Cheers, Gus

Bruce

[H.A.]

.

[bdosborn]

Sorry, Tex, no simple way to put it. It will work but it won't be optimized for less than optimal conditions.

Hmm, this brings a few questions to mind:

What are the less than optimal conditions? When the panels are in the shade. See Shadowcatcher's post. How large of a gain in harvest will the "optimized" approach yield? Apparently enough to keep Shadowcatcher's batteries at 75% charge. See his post.

Low light performance is more a function of the panel than the controller. I'd be very interested in what Shadowcatcher's amp-hrs harvest per day was in the shade. He has a nice battery monitor so maybe he can share that with us. However, I think its important to point out that the panel shown in the OP will work just fine in most instances. There are better performing panels for low light situation but they absolutely won't be cheaper. Its pretty easy to chase the 9s with PV systems and the gains diminish quickly while the cost skyrockets.

And since when is voltage drop proportional to the square of the resistance, did they change Ohm's law when I wasn't looking? Geeze, nobody's perfect. Note the time of the post. Why was I up? Because I was in pain (as I virtually always am) that most folks can't begin to imagine. I was thinking of power=I(squared)R. Opps. At least I wasn't thinking PV=NRT or D=1/2AT(squared), °C x 9/5 + 32 = °F, or something totally irrelevant.

Sorry, I couldn't resist that one.

What alternatives do recommend that will yield a higher solar harvest and what is $/watt? I think Shadowcatcher pointed out the advantages of a MPPT charge controller and panels in series. This combination of panels and controller will charge a battery when a single panel or panels in parallel won't as in when the light isn't as bright due to clouds, shade, solar eclipse, or nuclear winter. Cheers, Gus


An MPPT controller is usually good for a real world improvement of 10% in solar harvest. For the 100 watt panel shown in the OP that's a 10 watt increase. However, the cheapest, quality MPPT controller is around $220, which is $170 more than the PWM controller I posted a link to. That's 10 watts for $170. I'd rather buy another 100 watt panel as its around the same price per watt as buying the MPPT controller. MPPT isn't cost effective on smaller systems under 600 watts. It does make sense when you want to use a higher voltage panel like Shadowcatcher did or you're out of roof space and want to wring ever last watt out of your panels.

I think the bottom line is that the PV system shown in the OP will work fine. It won't be the most efficient performing system available but it should easily keep up with byrdz1's electrical needs as long as he realizes the panel will need to be in full sun.

Bruce