# RV solar power for keeping house batteries topped up....



## SidecarFlip (Mar 28, 2015)

Unlike most posters on this site, I did do a search but basically came up with zip.  I need to move my RV from where it is (next to my shop, plugged in to shore power) to a basically remote location near my hunting property in northern Michigan.  The RV will sit on a friend's property next to his barn but so I can access it for lodging during hunting trips and as a 'garage' if you will, for my quad which I will use to travel my property.

While I can shore power the RV via extension cord to his barn, I prefer to run self contained for the most part.  I will have my Yamaha Inverter generator with the camper so that if my wife and I want to go up in the summer, we can run the roof ac, however, most times it will be minimal power usage except keeping the Quad battery charged and using the 12 volt power for interior lights and the fridge (propane/12volt) when we are 'staying' in the camper for hunts.  The propane furnace is also 12 volt powered.

I run a pair of Group 31's, 1000 CCA flooded cell batteries and the RV is pre wired for an on roof array but has no charge controller and no panels.  The install will basically be flat on the roof but the camper will be sitting in the open with no shade.

I'm not going to be there every weekend but I need the panels to keep the house batteries charged and my quad's battery charged and of course the CO detectors and  the on board electronics operating and, it gets cold here too.

I won't be using the plumbing and the tanks will stay drained and winterized.  If I need to use the 'facilities' I have 120 acres of woods all about.....

I'm thinking that a simple charge controller nothing too fancy and a single large panel would handle the electrical needs but I'm not sure and I need some guidance.  I can do the install myself, just need to know what I need to get it operational.

Thanks in advance.  I need all the advice (preferrably good advice) I can get.


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## jebatty (Mar 29, 2015)

You may find the info you want on the RV  forum here in this PV forum website:
http://forum.solar-electric.com/forum


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## sesmith (Mar 29, 2015)

We use solar charging exclusively on our sail boat.  To start with, you'll have to make some calculations to see what your energy needs are.  Add up the amp hours of all the things that will be running off the batteries in your rv.  You can use a current probe on a multimeter to check each circuit and measure amps. when on.  Estimate how much use that circuit will get in a 24 hour period and multiply the amps measured times hours used.  Add it all up, and make sure you have enough battery capacity to cover you when the sun isn't shining, without depleting the batteries too far.  Then just make sure you install enough solar capacity to make up for what you use in a 24 hour period.  Give yourself some leeway for days that don't produce much sun.  If you don't want to measure things, see what other people are using on some of the rv or boat forums, and use that as a starting point.

When it comes to controllers, there's always the debate between using mppt and pwm contollers.  pwm controllers will be quite a bit cheaper.  I've always used one of the better pwm controllers, as I doubt I'd see a difference worth the added expense of an mppt controller, but that's just my opinion. Either way, cheapest does not usually equal good, whichever type you go with.

One tip I learned is that you can reduce your electrical needs quite a bit by switching all your interior lighting to LED.  We did that, and also switched our mast light (used for overnight anchoring) to LED.  You don't have to replace fixtures.  You can usually find replacement LED bulbs to replace the incandescent 12v bulbs in the existing fixtures.  Also, if you need additional lighting, the LED strip lights, I'll link to below, work really well under cabinets, recesses, etc.  They can be cut to length as needed, and there's also a dimmer than can be bought separately...make great "mood" lighting.  Just make sure you get the warm white color, not the cool white (same with your replacement bulbs).

http://www.amazon.com/LEDwholesalers-Flexible-SMD3528-Adhesive-2026WH/dp/B002Q8V8DM


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## SidecarFlip (Mar 29, 2015)

The LED bulbs are a fantastic idea for the 12 volt lighting.  I replaced the tail light bulbs in my motorcycles with LED bulbs and I should never have to replace them again.

My situation is I'm not using all that much power at any time but I want the camper batteries to maintain the quad battery and the on board smoke/co detectors.  Not much draw in actuality and I'm going to replace the 12v bulbs with LED's thats a good idea.

I don't want to shore power the camper using my friend's 110 volt outlet in his barn if I can keep the unit charged up with a roof panel or 2 with a couple group 31 flooded cell batteries...

It won't be an every weekend adventure, the camper will sit for long periods with no one using anything.


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## dougstove (Mar 29, 2015)

LED are intrinsically DC, so I think the gain over incandescent or fluorescent would be even bigger in a 12V DC situation, than in a 120V AC house wiring, where the LED unit has an inverter built in to the base.


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## SidecarFlip (Mar 29, 2015)

I actually have 8 double bulb 12 volt fixtures in the camper so thats 16 LED's not including the outside lights which are also 12 volt.  All in, thats 19 bulbs.


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## jebatty (Mar 29, 2015)

LED's typically are about 1.7-1.9vdc and multiple LED's in series frequently are used for a 12vdc bulb. Some lamps may have boost/buck circuitry to allow them to stay bright as battery voltage drops or to have multiple brightness levels. Amazing invention.


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## sesmith (Mar 29, 2015)

The last incandescent bulbs I swapped out for LED's, on our boat, were more than 20 watts.  The LED replacements are 3.2 watts, so a pretty big improvement.


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## mellow (Apr 1, 2015)

With an open area I would recommend trying out the harbor freight solar kit, it is built on the cheap side but it works:  http://www.harborfreight.com/45-watt-solar-panel-kit-68751-8527.html

Use a 20% coupon or wait for a good sale and use the coupon and you can get it for a good price.

I check our local store for returns and have found some good deals.


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## midwestcoast (Apr 2, 2015)

Since you're not there using it much I don't see a bigger PV system being worth it.
Your generator & batteries can already give you what you need while you're there.  If you only have some LEDs, propane furnace & propane fridge going, a good charge on the batteries can last quite a while.  
What about when there's a foot of snow on your flat mount panels? Are you going to go up there after every storm to clean them off?
Why do you need CO & smoke alarms on when no-one is there to hear them & nothing is running?
How about a little 5 or 10 watt panel sitting inside on the dash trickle charging the batteries & just disconnect everything else when you leave?


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## Where2 (Apr 2, 2015)

There are SO many ways to do better $/W on solar panels than HF. The 220W panels on my roof were $0.78/W. At that cost $/W, the 45W HF kit should cost $35.10 Somehow, HF charges $3.38/W even with a 20% off coupon??

A host of 12V panels with aluminum frames can be found in the $1/W to $2/W range. I see some 90W and 60W panels for $1.6/W-$1.9/W. 50W panels for $1.8/W


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## woodgeek (Apr 2, 2015)

For <100W panels eBay seems to have the best prices....amazon stinks.


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## iamlucky13 (Apr 3, 2015)

To be honest, there is an advantage to shore-powering your camper since you have the opportunity, to prolong the life of your batteries. If you're not using the camper regularly, the cost of the electricity you use will be very low. And if you've got a dual-power fridge that can run on 110 VAC when available, it will save you a lot of propane.

Still, if you like being self-contained, especially if you use the camper elsewhere, the cost of a small solar setup like this is pretty reasonable these days.



mellow said:


> With an open area I would recommend trying out the harbor freight solar kit, it is built on the cheap side but it works



I'm not one of the anti-Harbor Freight folks, but their solar kits are a joke. I don't know why, but their solar panels are more expensive than other sources for a lower quality product. 

Even Home Depot sells (by ordering and shipping, not in-store), better solar panels for a much lower cost per Watt:
http://www.homedepot.com/p/Grape-So...t-Systems-GS-Star-100W/204211365?N=5yc1vZbm18

You can get slightly better prices through Amazon, and I'm sure even better through Ebay, although I've always wondered about the quality of products coming from discount sellers on Ebay.

The above doesn't include the charge controller or wiring bits that the Harbor Freight kit has, but it's twice the rated output, and actually physically slightly smaller, for a lower price. Amorphous panels like Harbor Freight don't see their output decline quite as much in cloudy conditions as the polycrystalline panels that make up the majority of what gets sold these days, but polycrystalline also have lower performance degradation over time that will roughly make up for that. And the better pricing of non-HF panels more than makes up for the cloudy day performance.

If you can get a decent estimate of your daily usage, a couple of us can estimate how many Watts is appropriate. However, if you already know your existing batteries are enough to get you through a typical weekend, then a single 100 W seems like an acceptable start. Self discharge from both batteries should be less than 10 W-hr per day. A 100W panel should exceed that on even the darkest of cloudy days. Recharging after use for typical sun levels would take several weeks in the winter and several days in the summer. This is below the ideal charge rates, but as far as I know, that should only slightly reduce the life of the batteries.

It seems like there's lots of options for 30 Amp charge controllers, which will handle up to 3 similar size panels total.


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