Hi James and others,
I have 900 watts of solar on my 2002 and...it is none too much. When at ..
Quartzite I always had to run the generator in the mornings. So...there isn't such a thing as too much solar.
Just as a reference I have a Xantrex RS3000 that I have feeding the whole coach. During summer I have used the air conditioning on inverter for a limited time (15 minutes or so) when I stop the generator to register at an RV park until we get plugged into our site. Pulls 150-160 amps according to the Trimetric battery meter. While the compressor does pull a lot of current at startup the inverter will have some surge capacity too. It's my understanding that it's surge capacity is one of the things that differentiates high quality from low quality inverters. I haven't researched this in a long time but I don't think there's a real good measure of the surge capacity that makes it easy to compare models and brands. I'm really not up on all this so take it with a grain of salt.
Your real world experience is exactly what I would expect with solar and inverter. A good quality inverter with a high short term overload capability will start the AC. If you add the soft start option, it would help a lot. As you note, the running current draw is around 160 amps---- house batteries won't stay up long with that current draw. Deep cycle batteries don't like short term high inrush currents, such as 600-700 amps momentarily to start the compressor, it will affect their life over time. Unfortunately, there is no free lunch, especially with energy.
I'm old school, personally, I'd rather buy a couple of gallons of diesel, crank the generator and run both AC's!
On the Escapee's (SKP) forum (Escapees Discussion Forum (http://www.rvnetwork.com)) one member, "Reed and Elaine", have about 2kw of solar and a big Lithium battery bank running at 48vdc. You might want to slide over there and see some of their posts.
One issue you may run into is fitting that much solar onto your rooftop.
I'm only running 640-watts (in a series-parallel circuit) and it's also not quite enough even though we're pretty frugal with out power usage. Especially in the winter months. So there is clearly (to my mind) no such thing as "too much solar". Unfortunately the geography of my rooftop (or would that be "topology"?) is not especially friendly to more solar. If we need to run the generator we do and no apologies for it (although not at inappropriate times depending upon where we are). Generally the mornings are the best since that's when we'll be more interested in coffee machines, microwaves and toasters. And a heater.
Craig
Generators average .5 GPH and last with regular maintenance will last 6,000 - 10,000 hours. To each their own, but that seems more effect than rally expensive solar arrays and batteries.
I will add solar to my coach when I full time, but will have no concerns with finding a campsite with a power pedestal or running generator.
Seems a little oxymoronic - having 450 HP diesel to move the coach from campsite to campsite, and then worrying if I have to run the ten set for a couple of hours per day...
The Organic Rankin Cycle heat recovery turbine system is indeed quite cool... Partial pun. :-)
There are some more efficient A/C units that don't take quite 160 amps. One of the units I was looking at claims to use about 11.2 amps 120 which works out to 1344 watts * 1.1 (to correct for about an average 90% inverter efficiency) = 1478 watts coming out of the battery bank. dividing by 12 volts that gives you about 123 amps. The battery bank we're looking at provides about 933 (usable amp hrs 1120 amp hrs overall with 80% DoD which Lithium is ok with ). So, that gives us a bank that can run the A/C for about 7.5 hours. Granted that's excessive and doesn't count any other loads. But we're not planning on running the A/C all the time, just want to have it as an option for when we're in areas that are marginal heat/humidity wise. We would be using the generator periodically in any case where we were using the A/C for any substantial amount of time, but the battery/inverter would allow us to cut the run time quite a bit and the Solar would allow us to meet all other loads (during decent days) and stockpile energy for cloudy days.
We're neither crazy nor delusional, and have no expectation of running an A/C on a regular basis using Solar. We're just trying to provide it as an occasional option, and it's useful as a design criteria, because if we can run an A/C on the batteries for short periods we should be able to handle just about anything else. Make sense?
I'm not opposed to running the geneset when needed, but I'd like to run it as little as possible for any number of reasons. Most of the time our existing energy budget will be met mostly by the solar and the large battery will pick up the slack for an extended time especially when the weather isn't solar friendly.
I'm sorry if peace and quiet is a priority we put more emphasis on than others. I suppose that's why I always enjoyed and lived on sailboats and not powerboats. I used the diesel on my boat when needed as well and I took care of and pride in it's maintenance as part of the boat and because it was a great piece of machinery. But given the choice I always used the sails and greatly enjoyed it. When we go out into a pristine area of the country and park for a few days to enjoy it, I'd like to be able to do it mostly without running the genset for much the same reasons.
I'm sorry if that doesn't make sense to some folks here.
To me, the choice to take the family on the road on enjoy the country for a couple years while the kids are young enough to do it is not about the optimum use of money. If it was, do you REALLY think a 42' RV would be the the most economical way to go? Does a large Solar array and lithium batteries pay a financial dividend over running a generator all the time? No. Of course not. It DOES give us a tremendous amount of flexibility. It will let us stay in parks with no hookups without running the generator all the time. It lets us make the generator a system that's there when we NEED it, but not something that we need to run all the time.
James
I'd really rather not derail the whole topic into a defense against solar bashing thread, and I'm quite sure that's not what others intend. I appreciate what I believe to be an honest effort to make sure we know what were getting into and make sure that we're not delusional. :-)
It did seem like there was a bit of a "piling on" going on there though, so I felt somewhat obliged to clarify things a bit.
@wa_desert_rat Thanks! That's a resource I had missed and might be very useful to us indeed. :-) I swapped posts with Chris from Technomadia and he also suggested looking at 24 or 48 volt systems due to the efficiency improvements all around, but I'm a tad concerned about the complexities of supporting the existing 12 volt system if we move everything else to 24. I suppose one could always put in a 24 -> 12 volt transformer, but I imagine there are a LOT of potential gotchas in such a scheme. Keeping it simple and staying with 12 volt is likely not the most efficient system, but likely to cause less unintended consequences. :p
Regarding the geometry on the roof: I hear you! We are lucky enough to have a quite large section on the back of the rig that's completely open and AM Solar sells a panel that (with feet) could be mounted with two end to end almost exactly stretching from one side to the other with one inch in between. There's enough room for 4 rows like that for a total of 840 watts on the back. We're planning on removing the defunct satellite dome from the front, which will allow another similar block on the front and then we can run panels along either side in the areas where the A/C units run down the center. There's some question of exactly how the geometry will work out so I don't know exactly what we will have on the roof and whether we will add a ground array. We may also add a wind turbine or two to pick up some of the generation slack for stormy days.
Still hashing out the details but really enjoying the process so far and appreciate all the helpful insights and suggestions! :-)
James
I don't think anyone was bashing solar, here. Certainly not me. I was a certified (or perhaps certifiable) pioneer in the use of solar power on a cruising sailboat beginning in 1981 when I bought two 33-watt panels in Oakland, CA (on our way through from Puget Sound). Then I carved a propeller on the beach in the La Paz area, connected it to a 36-vdc motor, strapped it to some galvanized pipe and had a wind generator.
Reed and Elaine (on the Escapees forum) have run their A/C on their solar system. Their comments are worth reading. 2kw of solar takes a lot of roof space, though. It's worth it to read the remarks about solar and inverters there... and, of course, there is a cruising forum with over 4,000 posts about solar and lithium battery systems. That one I have not yet tried to get through.
I'd put more up if I had it. The solar panels and the charge controller seem to have become the cheapest part of the equation now. I have under $1500 in my 640-watts but it would take $4,000 worth of lithium batteries to equal my wet-cell bank. I'm hoping that in two years when the DW retires and we can take more than a month at a time down south things will have equalized a bit. That technology is still shaking itself out (as Technomadia discovered).
Nice to have pioneers. You have no idea how many people asked us what those funny things were on our sailboat while we were quietly anchored in a tropical bay. We had just enough power to give the DW and I enough ice (from the Adler Barbour refrigeration system) to have one drink in the cockpit at sundown.
Craig
Whatever the RV's internal system voltage, you probably want to give serious consideration to not just having 12vdc panels wired up to deliver 12vdc to the solar charge controller. There some talk now that there may be some inefficiencies running MPPT solar charge controllers at 12vdc input from the panel array. They're saying at least 24vdc and higher if possible. I think Pierce (on this forum) is at 140vdc from the panel array into a Classic 150 but he has a KW up on his U300. Reed (IIRC) is running about 90vdc with a series-parallel system. Higher voltages from the solar array simplify a lot of things. I am 108 (panel voltage).
You can't use a transformer to change from 24vdc to 12vdc but you can use a converter. Reed seems to have that covered. I'm at 12vdc because it's just simpler and for me, with wet cell battery bank, it makes little sense.
Lithium battery banks are a lot more finicky about how they are treated than wet-cells or AGM or even Gel. I have not waded very deep into that issue yet as I'm hoping that time will simplify it.
Craig
So if you're running the panel array at 108, does the charge controller convert that down to 12? I haven't gotten too deep into that side of things yet as the actual solar install is a bit down the road. I've been focused on trying to get a handle on the other aspects, but it's becoming clearer that avoiding re-work really requires a more holistic approach to the whole project. Have to say I'm very impressed with the Victron system, especially the new Color Control GX (Color Control GX - Victron Energy (http://www.victronenergy.com/panel-systems-remote-monitoring/colorcontrol)) system. Their batteries are prohibitively expensive, but some of the synergies between their inverter/charger MPPT solar controllers etc are impressive.
James
I'm certainly not bashing solar-- I have a ranch house (well, a hunting shack anyway) on a ranch in south Texas that I have been running off grid on solar power since 1979, and it is still working great! No air conditioning of course, just a power water system, and lighting. I built the system with solid silicon slab PV cells encased in low lead glass, now that's old school! This type of solar panel was first used in our area for off shore oil production platforms in the Gulf of Mexico that did not have other power sources.
Like others on the forum, I have used alternate energy sources on my sail boat. I currently use an AirX 400 watt wind generator on the boat, and it has been a great addition! Of course, the wind profile on a boat in the trade wind belt is a bit better than on a motor home.
I agree with what others have said about higher voltage solar systems. Over about 600 watts, the efficiency is better using a higher voltage inverter-- lower current wiring equals lower loses.
I am currently involved in development of a 4000 acre solar site in north west Texas for commercial application (independent power producer for utility interconnect). Fun stuff, but that is a different subject.
With limited real estate on a coach roof, how much power you can generate and use effectively with PV solar is limited. Thus my comment on practicality. If however, your motives are different, developing, using, and taking pride in you own solar system is fun and rewarding!
Yes, exactly. Having the higher voltage means that I can use much smaller wiring from the solar array down to the charge controller because the current decreases with higher voltage despite the same power; and current flow (amps) is what you have to design your wiring sizes to.
I should also explain that panel array voltages can be confusing. In order to charge a battery you have to have a higher voltage than the battery so solar panels always have higher no-load voltage than the load they are designed to charge. A 12vdc panel has a nominal voltage of 12vdc but it's actual voltage is usually somewhere around 17vdc. A 24vdc (nominal) panel typically measures 36vdc with no load.
I opted to use the Midnite Solar Classic 150 even though the price of the unit ($600) was pretty much the same as the cost of the entire panel array! Mostly because the Classic 150 is capable of handling my system easily and is very configurable (as well as upgrade-able in terms of operating system). Earlier I had installed a TriMetric 2025RV unit which I keep simply because it's so easy to use. The Classic 150 will be able to handle more solar (if I can cram more on) as well as any battery system. The Classic 150 also display the no-load voltages of the panels even though there is a load.
We also had to remove a DOA satellite antenna as well as a huge storage locker to make room for solar panels. I like having the ability to walk on the rooftop so that is a factor in my installation. Some people just do away with that and do all their maintenance from a ladder.
One of the Escapees, Jack Mayer, has a web site dedicated to information about solar systems that is probably worth reading.
My solar array is wired in series rather than parallel which adds the voltages (parallel wiring adds the amps) but also presents some greater sensitivity to shading. But on my rooftop shading would only be a problem in early morning or late evening... or bird poop. :P
Craig
Bumping this because Chris Dunphy just posted an excellent article on what would be required to run an RV roof A/C off solar:
The (Almost) Fantasy of Solar-Powered RV Air Conditioning | Technomadia (http://www.technomadia.com/2015/02/the-almost-fantasy-of-solar-powered-rv-air-conditioning/)
Since it was discussed personally I think all the people going with giant solar arrays are nuts ;) I would instead spend the money on a honda 1000 generator - just enough generator to get my batteries charged. After all I don't want to boondock in poor weather.
But the idea of a big lithium ion battery bank so that I can run my air conditioner overnight during hours when generator usage is offensive? That's an intriguing thought. You could then also recharge with the big generator since the lithium battery can accept a VERY large amount of charge very quickly. You could get that bank recharged off a 10kw generator and a properly sized charger in no time flat.
All "early adopters" of new technology are "nuts".
But God bless 'em, every one. Without them the manufacturers of cutting edge equipment would never sell enough of their products to stay in business. And if they didn't tell us what they are doing then we'd never know about the stuff at all.
Craig :)
my gen is noisy in a quiet area. more batteries and more solar keep the run time down
Exactly.
I went four days and three nights before needing to run the generator at Quartzsite this past January.
This is with a modest 452 Watts of solar and low angle winter sun, a 12 Volt only 14 cubic foot marine refrigerator, and using only LED lighting. The propane furnace was probably the main power user at night.
My last morning there, the batteries were at 50% of rated capacity and I ran the generator for awhile before starting the engine and heading out.
While at Q this year I sure missed the 500w I have on the Lazy Daze. Found the noise of the generators, including my own to be more annoying for some reason....maybe age ? Looking last night at panels, it appears to me that the price is headed back up, or is it my imagination?
No, they will be staying down and may drop further. You just have to search a bit rather than going to a solar company and paying list.
Here are a few panels much like the panels we have on the roof of ours: 7 - 290 watt Canadian Solar Panels (http://sfbay.craigslist.org/eby/ele/4914132748.html)
On Craigslist, $0.55-0.65/watt will buy excellent panels. Then about $620 delivered for the controller. Figure about $1600 total for 1100 to 1200 watts complete with wiring, connectors, etc. Batteries can also be found on Craigslist for excellent prices. That's how I found ours. Batteries doing great 5 years later.
Agree, nothing worse than generator noise in the desert.
Pierce
Took your advise, found some panels local ( well, in Houston ). Now if I could figure out how to run wire in the FT! In the LD I poked a 1 1/2" hole and ran a plumbing vent fitting terminating in a cabinet. Used the same penetration for antenna runs. I'd like to run in the channel by the drivers left shoulder, down into the battery compartment. How to get from the roof into that channel ?
what I did was run from roof down fridge vent/area then behind kitchen cabinets down to bay then along centre wire run into back wall of battery bay. I used #2 wire and it was a tough pull but worth it. My MPPT controller is in middle bay across from electrical panel, then I did the centre run to battery. Put in a 2 breaker (I used 70amp) box so you can switch off batteries or solar power independently.
It goes fine once you start. I also have a Trimetic panel on side of lower cabinets facing the front for ease of checking charge rate and battery condition.
JohnH
Dave W.,
Check out the photos in my old post. All Foretravels are different and even the roof layout is different depending on year, length, interior layout, etc. Ours is earlier and I went down in a different spot, just behind the fridge and used the top can door/compartment to mount my controller, circuit breakers, etc. Perhaps others may have installed the wires as you want to on late coaches.
I like to have the controller where I can see it with the breakers close by. Use the solar wire, not the low voltage stuff at HDepot. Just as inexpensive off ebay. I then used welding cables to essentially bring the battery (actually, to a bus box in next to the wet compartment) to the controller. Connectors are super easy to install on the panel wires as they all use industry standard stuff.
Using gray electrical flex on the roof, I made it look as neat as possible with the wires inside and the panels installed about 1 1/2" above the roof so they will run cooler. This also shades the roof so you will be cooler in summer.
If you are running four 36 volt panels, it's not a good idea to run them in series as the cold morning voltage will be as much as 40 volts so a series installation would be 160 volts or ten more than the MidNite Classic 150 likes. I ran our in a series/parallel setup and the controller loves it. 24 or 48 panels are also good. No panels much larger than 100 watts are made in 12V.
The Classic 150 takes in any voltage up to 150 (in this model) and sends it to the battery at the correct charging voltage. Easy to do a default installation to get it going with dozens of settings you can make later. I like the model with the LCD display for easy time, date, voltage, etc. 5 year warranty and after that, $125 max to repair or exchange. Gets the best reviews off all MPPT controllers.
When you get your panels, post how many, voltage, a drawing for what the roof will look like and I will be glad to take a bunch of shots of ours and upload to a Picasa album and post the link. PM with questions. All panel information is on a sticker on the back of the panel.
In Q with a low winter sun and a flat installation, we maxed at 550 watts out of a potential of 1140 watts. Very happy with that.
I was a little careless a couple of times and got a pretty good shock from the 72 volts. Under the right circumstances, it could kill you.
Solar is the future! Post progress.
Pierce
We're running the wires down the fridge vent too. Splitting the solar panel install up into phases so I can get my feet wet with a simpler install before I get started trying to optimize the final layout.
We're going with 2 groups of three 160 watt panels from AMSolar (one in the front, one in the rear) each set wired in series and run back down the fridge vent to it's own Victron 75/50 MPPT. I've got more details over on the Heading to FOT for Shadow Beast's major renovation and service visit. (http://www.foreforums.com/index.php?topic=23857.msg189135#new) topic.
Love the idea of using one of the can storage pullouts as a solar "panel"/bay, but I doubt I could get Susan to give one of them up. :p
I think I forgot to consider/include breakers in the parts list, how do you size and position them? Between the MPPT and the panels?
@Steve: The page title SEO replacement of the link above is wrong. I don't know SMF nearly as well as I know vBulletin and IPS so don't have any idea why it would be pulling to wrong title. Maybe it's picking up the post # instead of the topic # in the url?
ETA
@Tigratrus Thanks for the report, should be fixed now ... Steve
Here are four photos of exactly how I did ours. The mini box and breakers came from Northern Arizona Sun and Wind. 100 amps in, 100 amp out. I brought all welding cables into the wet bay bus and added a 250 amp fuse there just in case everything goes south. Welding cables go up to just behind the controller where a junction goes from welding cable to controller wires. So, there is a 100 amp breaker between the roof panels and the controller and another 100 amp breaker between the controller and the bus (house battery). The wet bay panel is a great spot to plug in the trickle charger to charge the engine batteries when on shore power. Easy and neat. I turn on the battery breakers first then the PV breakers. Shutting down, the PV breakers go off first and then the battery breakers.
Pierce
FWIW..
Did I read somewhere wire size over 100 watt panel reduces amps to the battery. :o Multiple panels in series compound the flow? NOT EXPERT whats the cost differnce with #8 copper stranded thinn?
Since your doing this DREAM lithium ion possibly air conditioner system. Nows the time!
So cool 8)
Double the voltage (wire two panels in series) and reduce the wire size by half for the same loss. Here are the wires: solar panel wires 50 | eBay (http://www.ebay.com/sch/i.html?_odkw=solar+wiring&_from=R40&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xsolar+panel+wires+50.TRS0&_nkw=solar+panel+wires+50&ghostText=&_sacat=0) Pretty inexpensive for an installation.
Easy to cut, easy to install connectors and then just make the connection to the next panel. As I said before, I ran all the wires inside a flex plastic conduit and then put the connectors on as they were too big to run through the flex.
The Europeans get away with much smaller wires with 240 volts for their homes.
Pierce
Panels in series the voltages add; panels in parallel the currents (amps) add. More amps means thicker wires.
While lithium (LiFePo <--- see how cool *I* am) would be nice, I don't even have AGM batteries. In fact I just ponied up $200 for another 8D wet-cell (old fashioned) truck battery. We won't be traveling seriously until 2017 and by that time maybe some of the tech will have shaken out. If I were leaving next week I'd get two new AGM 8Ds. Right now I have bigger things to break my budget with than batteries.
The goal - at least for many of us with solar - is to have the house battery bank charged by noon most days. And I do not hesitate to start the generator up in the morning to get the coach up to temperature, run the microwave for breakfast, and to get coffee ready. And if it's really cold I'll run the gennie in order to run the block heater. I like solar a lot but I don't have to be stupid about it. :P
But on most reasonably sunny days my batteries are charged around noon-ish and from then on the juice is free. So I charge up my lithium battery booster, charge the little 3-wheel scooter I need in order to keep track of the DW in Costco (and the scooters they provide are just way too sloooooowwwwww), charge laptops, tablets and cell phones and maybe let me turn on the electric blanket for my afternoon nap.
I appreciate the guys with 2kw and the LiFePo battery banks. But I just don't have the $8k to throw into that. And, besides, I don't have the room for enough batteries to soak that power up (although the LiFePo batteries are much smaller watt-for-watt than any other).
My motto has always been: "Any solar is better than no solar and there is no such thing as too much solar."
Craig
Craig, like I said NOT Expert but with his proposed phased in set up an adding enough battery to run ac a bit, although voltage may flow to charge battery with ac running he may need amps.
Im lucky.. my 900w with 1 agm stays at 13.6 for 6 hours, PO did a lot of calcs justifing 1 house battery like your wet cell.
I agree with you whenever the need I run the genny.. with a 10000 hour cycle thats 416 days @24/7 ^.^d
I you are trying or want to run a 115V AC off of an investor and batteries - LRA (Locked rotor amps) on start up can challenge some investors - Dometic OEMS a soft starter from Hyper Engineering (Waterfurnace International) to reduce LRA by 60% on start up, so that your investor is less likely that your inverter will trip offline. There are Youtube videos of how to hook the device up on a 115V Dometic marine A/C, which is often used on large boats to run the A/C only at night on a 2000W Honda super quiet generator. These A/C's still sully pull in the neighborhood of 13 amps running (RLA) so that needs to be considered.
Full disclosure, I am the largest distributor of the Hyper Sure Start.
I have been meaning to put two of these on my A/C;s and test, but didn't do it last fall, will have to do it this spring.
(deleted one line from above post to avoid conflict with user agreement - Michelle)
Not sure if this is the right response, but in my understanding:.
As you increase wattage of the PV array you encounter greater and greater resistance to the electrical current passing through the wires down from the roof. There are two primary ways to deal with this: higher voltage and thicker wires.
We can look at thicker wires, but wiring the 3 panels in series increases the voltage (55.5 volt Vmpp ) to the point that the loss should be pretty small. I suppose I should really do some research on what constitutes reasonable loss. I think Dave (AMSolar) said his estimator put it at about 1.4%? Don't remember exactly, but he said it wasn't something he would worry about. That's not to say it might not be worth using thicker wires, it certainly highlights an area I need to know more about, thanks! :-)
I have dealt with Dave and of course Greg one of the owners. They know more about solar than we all collectively will ever know. They did my first install then I replaced all the wiring with #2 cu stranded just to make it as "Loss proof as possible" I added panels and changed battery set up etc to get to where we are now.
Great company and can trust them.
JohnH
Yes, it can end up like trying to fill a swimming pool with a garden hose. The higher the voltage (up to the max the controller will handle), the better. Considerable loss possible between the controller and the house batteries unless you use big welding cables. A little percent here and there add up to more time to bring the house batteries up to float voltage. You just have to size the panel wiring so the maximum voltage into the controller is down about 10 percent from the rated input to be safe on very cold mornings when the panels will go over rated voltage.
I have seen several neighbors who had their solar RV installation done by professional shops. They were not happy as none worked correctly. If you do your research, you can do a better job than many shops. Some will do an excellent installation but others won't and many owners don't really have an idea if their installation working up to it's potential.