What size solar?

[A_K_Chesnut]

Hey everyone! My wife and I are new RVers prepping for full time starting this August. We intend on boondocking as much as possible, so naturally I'm trying to learn about solar. Let me tell you, my head is SPINNING. I've been researching pretty heavily for days and I'm really not any closer to figuring out what to do. Some say atleast 200w, others say even more. Everyone says don't buy Harbor Freight, so that's helpful. Looking at systems, these buggers are expensive. I'm perfectly capable of installing a setup myself (and even have some knowledgeable help), but I'll say right now a $2500 system is NOT in the budget! I don't mind having to run the gennie a few times a week, but want to stay away from the several hours twice a day deal that many are describing without solar.

 

Could I get some help? I'd love to list our RV and expected electrical usage and maybe get some guidance on a good system or two? We have a 1993 Tioga Montara Class C, 23'6".

• One 12v house battery - do we have to add another? I don't have a good spot for a second, the current one is housed under the top step and there isn't any more room
• We will be moving with the weather, staying away from very cold and very hot climates as much as possible
• Will be swapping to all LED interior lighting - I suspect we will have two lights on for maybe 3 hours a day (we enjoy other light sources and use mostly candles for light in our home)
• Electrical panel for the fridge
• Water heater - I doubt we'll be using this often, water is easily and cheaply heated over our outdoor wood stove. Easy to pop on the gennie if we have to have an indoor shower (we love gym memberships for the free showers after a nice workout!)
• Water pump - This one is hard to say how much we'll be using, but I will have a water setup outdoors for dishes and general washing
• Window fan - I have a hard time sleeping in the heat and need some airflow. A small 12v fan propped in the window running at night will do the trick
• A/C - will only be used when our gennie is running or attached to shore power
• Furnace - We have a great little portable catalytic heater we can use instead of the furnace
• TV - I'd love to be able to run a small LED TV, say 20" or so. We enjoy watching movies now and then. So lets say we watch a movie twice a week. If I can get a solar setup that can handle this, I'll snag a 12v TV. If not, will just get a regular one and run the gennie for movie watching
• Small portable electronics, such as laptop/tablet/cell phones - I'll have one or two large powerbanks for charging these. Will charge the power banks while at work (we'll be working part time). Would be great to charge the banks occasionally off solar

Hopefully I have everything covered? We're long time "stealth" campers, but this is our first foray into RVing. Thank you in advance to everyone for your help! I'm sorry to say I wasn't able to come to a reasonable conclusion on my own.

 

Here's our new home, our first night boondocking on the drive home to Denver from Dallas

 

 

[Ronbo]

You will definitely need more battery capacity. You need to find s location where you could put them and also install your inverter. Once you get that sorted out you can start with one panel and a charge controller. Put a combiner box on the roof and wire it with at least 5 wires. That way you can add more panels as you get the money. Those wires will feed a box with disconnects. This is where the feeds will actually be combined. Then add a sub panel for the items powered from the inverter. You will be good to go here for a start. I paid $1000 for 4 $255 watt panels, $700 for charge controller, $1800 for inverter and just spent $2700 for LiFeMnP04 battery bank. You will also need cables, combiner and conduit. Roughly $2000 to get started as I stated above if you are doing the work yourself. Start reading here http://www.jackdanmayer.com/rv_electrical_and_solar.htm

[A_K_Chesnut]

Copy that, a second 12v deep cycle battery and a battery minder will be the first purchases. I know to add in parallel, I'll see if I can modify the current compartment to fit a second battery or if they'll both have to be moved elsewhere.

 

I like the idea of getting setup with everything and just one panel. Gives me a chance, with the battery minder, to see how much juice we are really going through. Shall I assume you're talking about 100w panels?

 

Not sure I'll bother with a sub-panel, at least not at first, as I don't expect to run many things off the inverter. As such, I don't imagine I'll need an $1800 inverter either.

 

How many amp charge controller should I consider given my hopefully low power needs?

 

Thanks Ronbo!

[Ronbo]

The larger the panel you can get the better off you are. You are going to pay about $1 per watt. More watts = fewer panels. Talk to the companies that install comercial systems. Mine were left over from a job by the co that did the roof of the VA hospital inHouston.

[A_K_Chesnut]

Start reading here http://www.jackdanmayer.com/rv_electrical_and_solar.htm

 

 

Oh, and thanks for this link. I've been pouring over his information as well, with continued head spinning... He lost me pretty quickly when he got into saying a $3k minimum investment is required then went on about microwaves and hair dryers and all sorts of things we have no intention of running!

 

EDIT: great tip to have a chat with the solar install companies, thanks!

[MrSeas]

Maybe something like this would allow you to "test the waters" of the solar life style....

http://www.amazon.com/Go-Power-GP-PSK-120-Portable-Controller/dp/B009MIPH4K

[A_K_Chesnut]

Maybe something like this would allow you to "test the waters" of the solar life style....

http://www.amazon.com/Go-Power-GP-PSK-120-Portable-Controller/dp/B009MIPH4K

 

Now that's a great little find right there. Bookmarked. Thanks!

[KRum]

Here is one for 1/2 the price...

http://www.amazon.com/ECO-WORTHY-Portable-Polycrystalline-Foldable-Suitcase/dp/B00MGLIIQO/ref=sr_1_8?s=automotive&ie=UTF8&qid=1458880602&sr=1-8&keywords=portable+solar

[A_K_Chesnut]

Where's the like button? HA. I think a "small," portable kit like this might work really well for us. After adding a second battery, battery minder and an inverter.

[Yarome]

Battery wise.. it depends on what type and size of battery you currently have. It seems as though your energy requirements are quite minimal. More capacity is generally better, but may not be "necessary". More info is needed.

You shouldn't have any problem running a 12v TV off battery for your modest viewing.

Unless I missed somethings... from what I read... I didn't really see a "need" for an inverter except to charge your powerbanks... occasionally. That could easily be accomplished by using your genset (since you plan to use one anyway) rather than going to the expense of an inverter install. Another alternative would be to charge your devices directly off 12v from your battery bank. Adapters are fairly economical and much more efficient than inverting your 12v to 120vac and then converting it back to 12v again for the actual device to use. Of course.. it's always something you could add later if it turns out you 'do' actually need one.

Generally, a combiner box is just that. All panel arrays will feed to the c-box.. either on the roof or inside your rig (if it's not that long of a wire run). From the c-box you would then have a single wire run that would connect to your solar controller. It's generally a good idea to have a disconnect in-line of the wiring from your c-box to the controller. You'll want to install a c-box that is capable of multiple connections, but it is not necessary to prewire multiple lines. The wiring from your c-box to the solar controller should be of an appropriate size to accommodate the maximum amount of current that your solar controller is capable of handling with the least amount of loss over the specific distance required.

You mentioned a battery minder. Those are generally used to maintain batteries when an RV is in storage for long periods of time and shouldn't be necessary. Your RV should already have a 12v converter installed (supplies 12v to your rig when plugged in/genset and charges your batteries). How good of one would be the question. An upgrade there might be in order.

As far as the size of solar controller... that would depend on how much current your solar panels are able to produce and the size of your battery bank. Both yet to be determined so it's difficult to say. With the size of your rig and available real estate up top.. I would "guesstimate" you'll probably be looking for a 30-45amp solar controller. Although.. if you're only planning on 200 watts max.. a smaller controller could be used. Part of that though would be what type of panels (low/high voltage) and how you will be wiring them (parallel, series, or parallel/series). That would also determine what type of controller (MPPT or PWM) would best suit your needs. Again.. not enough info to provide meaningful suggestions.

When sizing your individual panels it's important to find a balance between maximum space available against potential shading issues. Largest isn't always best. Ie., if your panel is 3" away from your top side A/C shroud.. shadowing may be a greater issue and 'could' kill better than 80% of the solar production of that panel (and every other panel if wiring in series). In that case.. a 140w panel fully clear of any shadowing issues would produce more juice than a 250w panel that's even partially shaded a good portion of the solar production day.

With limited roof top real estate you may want to look at high voltage high efficiency panels.. which will cost more than your run of the mill $1/watt panels, but overall will yield many times over the amount of juice.

Kit's can be an easy entry into the solar world, but generally speaking.. you'll get little bang for your buck and likely be disappointed with the solar production. For a quickie DIY project to help keep your batteries charged from point A to point B.. or an occasional overnight dry camp it might be sufficient. For a full-timer that plans to boondock as much as possible.. not so much. They are generally underwired and have less than capable controllers.

I would encourage you to take another stab at Jack's pages (and again if necessary). It can seem very confusing and a bit overwhelming at first, but focusing on one component at a time rather than trying to take it all in at once helps.

I would start with an energy audit. Understanding exactly what your power requirements will be is paramount.. including a working understanding of parasitic loads and equipment overhead.

From there.. I would start researching battery and meter options. Your battery bank is the "core" of your power system... along with the ability to effectively monitor it. Everything else is secondary.

Just as a side note on the 12v fan.. if you don't have one yet.. the Fan-tastic endless breeze moves a 'ton' of air and has very modest power requirements. Couldn't live without mine!

 

On edit: You might have run across it in your online research, but if not, "The 12 volt side of life" might be helpful. There are 2 parts.

[A_K_Chesnut]

Yarome, wow thanks. Gonna have to read that a few more times later to digest it all I think.

 

I was thinking of just using a smaller, inexpensive inverter because I won't be using it for much. I don't mind building myself my own little portable kit, say 100-150 watts instead of buying on premade. I do really like the idea of something portable so I don't have to park in the sun... battery meter! That's what I was meaning to get, not a minder. My apologies for using the wrong term.

 

I had come across that fantastic fan, it's earmarked for a closer look. Thanks for the 12 volt side of life link!

[bruce t]

If you search the internet you can find many example of how to calculate your use/needs. IMHO figuring out all the 'stuff' first is a pointless exercise until you know your needs.

 

We had a bus conversion with almost 2000 amp hours of house batteries. Four huge solar panels. Yet the system was 'just' adequate. You need to be very honest with your power use. Those sneaky phantom loads also add up. For example the start up amps on a water pump can also be a killer.

 

Once you are sure of your power needs then you can go shopping.

 

regards

[A_K_Chesnut]

Bruce, I was doing my best to put together a list of what I know we'll be using and how often. I had not considered the starting amps required for the water pump though.

 

Liking the idea of building a portable kit with a larger connection box to give me the ability to add panels later.

[bruce t]

Google will find lots of information

 

http://www.macandchris.com/electricalsystemsizing.htm

 

Do the sums. I've seen way too many folks spend good money on solar etc only find it simply didn't work for them.

 

regards

[Yarome]

http://www.macandchris.com/electricalsystemsizing.htm

 

I would be VERY careful with this particular link and other sites using simplified math for current calculations. They can lead to severe discrepancies in your total energy audit. Ie., a 5 amp AC draw is not always 50 amps of DC. Actual voltage must be taken into account or you could end up with +/- 5 amp discrepancy on a single appliance.

[bigjim]

I second what Bruce says about thinking it through before diving in too deep. I have 200W and currently have 2 dying 6v batt. I have had it at least 10-12 years and would not be without it but have seen some spend big bucks and end up not using it much. I occaisionally use a small 350Watt inverter mostly for a 12in 120V fan and a small tv and water pump and minimal lighting. Current TV is 12V. The big payback for me is some boondocking and boondocking while travelling. I did my own install with an experienced friend guiding me which was a giant savings. I didn't do the forum back then. He help a couple do their Whole House with even a small wind generator. They used it pretty good for some years but eventually fell back into using the grid more. ????? Me, I would like to have my own small set up for my room at the nursing home in case there is ever a power outage there.

[bruce t]

Sorry Yarmone I never checked the site itself. Rather I just used it as an example of all the information and calculations on the web that could be used.

 

regards

[Jack Mayer]

If you have minimal need for 120 volt power then you can likely get away with a pretty small solar system. You stated you have no need for a microwave or hairdryer - two of the biggest draw appliances in an RV. If that is the case, and you do not have a residential refrigerator - which you do not - then a small system should serve your 12 volt needs pretty well. That can certainly be done under $2000.

 

Regardless of how you proceed, you need to understand the entire system before you start to implement ANYTHING. Or you will likely waste money. My advice is to draw the entire thing out on paper with all of your design restrictions. And it you like, I'll be happy to review that. Simply email me.

[bruce t]

What Jack said. Find a good spreadsheet to list and calculate everything.

 

regards

[A_K_Chesnut]

Exact calculations will be done to the best of my ability! I can only guess on the draw of certain items and how often/long they'll be used.

[Jack Mayer]

Exact calculations will be done to the best of my ability! I can only guess on the draw of certain items and how often/long they'll be used.

And that will work just fine. Don't forget recharging of computers phones, etc. And if you have a router and aircard, you need to include it as well. These items "tend" to run all the time, but some people do turn them off when not in use.

 

Based on what you have said, you use VERY little power. Two golf cart batteries may be sufficient for your needs, at least as I understand them. Regardless, I'd be wanting to put in a good battery monitor (which you have already mentioned). In your case a Trimetric would work just fine. For panels I'd likely do a single rooftop, and make the rest portable. I say single rooftop because you mention stealth camping. In that case you may not always be able to put a portable out - and the rooftop will give you some solar harvest. It will also work driving around.

[The Quiet Assassin]

If you can; arrange to move your panels to follow the sun during the day as that gives you at least 50% extra.

 

You want a good MPPT controller. Some cheap controllers that claim to be MPPT are not. I use a Blue Sky 2000E to manage my 400 watts.

 

Avoid flexible panels.

 

Golf cart batteries are the most cost effective storage. Trojan T 105s are the gold standard.

 

Conventional laptops are power hogs, swap to a tablet.

[Yarome]

I think Jack's suggestion of using a split rooftop/portable setup is very sensible. As mentioned earlier.. if you would need another battery or not depends on what you currently have installed. With the little power requirements you have a 200-240ah battery capacity should be sufficient under most circumstances. Depending on your space limitations that could easily be accomplished with 2 - deep cycle 6v batteries (best option) or a single 12v deep cycle.

 

If it were me, I would try to map out my roof top to allow for 2 panels of equal size. Starting with one, but planning ahead to allow for another of equal size to be added at a later date. Ideally.. I would hope to fit a 150watt (+/- depending on the fit) high efficiency panel up top and a second to use as a portable (giving 300watts to start). If you don't discharge below 70% or so.. under average solar production.. 300watts should keep you up and running with only occasional genset use.

 

Adding an additional portable would allow for a quicker top off and probably some excess that could power fans or other light loads during the day without having to cut into your battery/ies.

 

Just a side note.. when doing your energy audit it's sometimes easy to overlook things like a power awning (if equipped), roof top vent fans, holding tank heater pads (if equipped), OTA antenna booster (if equipped), etc.

 

A lot of what is referred to as "parasitic" draw.. energy usage overhead that you generally just have to "live with".. can be mitigated to some extent by installing small 12v power switches. Ie., radio, water heater, thermostat... It's not a necessity, but when you're looking at trying to limit your daily power consumption to 50ah's or so.. even cutting a .25a 24hr load (6ah's) can translate to an extra 2-3 hours of TV time (28-39watt 19-22" 12v LED TV)

[VallAndMo]

Hi,

 

Here is one for 1/2 the price...

http://www.amazon.com/ECO-WORTHY-Portable-Polycrystalline-Foldable-Suitcase/dp/B00MGLIIQO/ref=sr_1_8?s=automotive&ie=UTF8&qid=1458880602&sr=1-8&keywords=portable+solar

Here's another also half the price but with much more & better reviews (100W instead of 120W, tho): http://www.amazon.com/Renogy-Watts-Monocrystalline-Foldable-Suitcase/dp/B00HR8YNK6

 

Cheers,

--

Vall.

[VallAndMo]

Howdy,

 

The larger the panel you can get the better off you are. You are going to pay about $1 per watt. More watts = fewer panels.

 

I'm not so sure larger is better, at least not always: smaller panels could lead to better roof space utilization, and therefore more Amps available. Also, more, smaller panels will (when wired in parallel) be more resilient against shadowing than fewer/larger ones.

 

Talk to the companies that install comercial systems. Mine were left over from a job by the co that did the roof of the VA hospital in Houston.

Now that's an interesting idea. I see from another post of yours inn this thread that you paid $255 for then, which I think is a great price.Can you please disclose exactly which maker/model of panels you got?

 

Thanks,

--

Vall.