Question:

to Neon (Practically Perfect) John’s blanket condemnation of solar power,sanyo solar pv panel  and aside from noting that it doesn’t take much to make the latter look silly, I won’t try to help Steve finish the job. But having some experience poking around in the alternate energy arena and trying to avoid being found amongst the loonier elements I offer some strongly held opinions that MIGHT be of interest to rv travelers generally: 1. So far, nobody has devised really cost-effective alternates to the power grid, assuming you have a cord long enough to plug in. Get that truth in yer head.  $$$ matter to all rational people. 2. Virtually all alternate sources tend to be situation-limited.  Solar panels to sunny climes, wind machines to windy ones, water power to dependable streams, wave/tide power to beaches, methane production to large herds, etc ad nauseum. 3. To varying degrees, the “free” sources are cyclic and/or intermittent and therefore create the need for power storage. To date, batteries are the most effective means of storing electrical energy… and at the risk of seeming to agree with Neon John I must admit they are inefficient and sorely limited. 4. For people who can afford the cost, space, and aggravation and who understand and accept the limitations, most of the alternate power schemes *can* reduce (or in unusual extreme cases) eliminate dependence on public power. 5. For the rv traveler, ONLY solar has very wide appeal, and it is only practical for a limited number of folks who live/travel in sunny climates, and/or who shun shade like the plague.  Investment in larger PV panels & controls CAN extend – perhaps even indefinitely – a generator-free stay in a sunny place, provided you are adequately frugal with power. We do not see any personal justification for solar, in view of where, when and how we travel.  But despite the hype from all sides, solar power is (about the only really viable alternate (non-generator) power source for rv travelers. Isanyo solar pv panel

Response:

Self-regulating promo?  WTF?  I used my battery maintainer (a device almost 3 ft long by 18″ wide and fully regulated via an external shunt regulator – hardly a toy.) as a convenient example because that is the only panel I now own, not being fool enough to get burned on solar twice. sanyo solar pv panel

Your panel is thus about 0.4 square meters. If rated at a 17V output, that would make it a 17W panel with a solar efficiency of 1.7%. You got TOOK John! Must be the experimental low-efficiency model.  I tried to go self-sufficient back in the 70s when government subsidy money flowed in great rivers.sanyo solar pv panel  I was not willing to adopt an austere lifestyle and thus found the concept impractical even though I literally had a roof full of panels.

So you are telling us you invested thousands of dollars coating your roof with PV technology, investing more thousands in a huge battery bank, certainly a power transfer switch to sell excess back to the utility, and you never considered your lavish life-style ahead of time? Come on, John, that sounds pretty impetuous to me – not the meticulously careful driver who can determine his fate on the road regardless of destiny and careless motorists! Ah, now we get to the crux of the problem – another one of those SoCal types who forgets that the rest of the world isn’t like SoCal.  The graphic at http://www.etaengineering.com/resources/insolus.html graphically illustrates the irrelevance of SoCal results to the rest of the country.sanyo solar pv panel  This graphic shows that SoCal gets nearly the highest solar influx of any area in the US.  SoCal gets over 3 times the amount of solar energy as New England and over twice as much as we get here.

Well, it’s encouraging that you now admit that there might be ONE area of the country where solar is a viable option. Could it be you are guilty of a slight hyperbole? Ok, let’s look at the chart. I am located and do most of my camping in the ‘orange’ zone. Someone in the ‘green’ zone would receive half the yearly insolation we do. If we lived there, we could get by as well with four panels instead of two. That is what this chart is for. I.e., solar would work as well or better as our system for about 1/3 of this country, and useable in about 90% of the country – according to ‘your’ chart. Let’s do some calcs using the figures from the above illustration. sanyo solar pv panel  I am biased heavily against solar.  I went through the solar stage back in the 70s.  It was impractical back then for anyone other than the stary-eyed zealots.  The only thing that has changed is that the current crop of panels are a bit more efficient.  Not enough difference to overcome all the other practical problems.  One of the biggest problems you’ll run into is that much of what you hear or read about solar is more wistful pining than fact.  The reason is solar is the darling of the environmental wing where most things are based on beliefs rather than fact.

<snip the rest of the hot air on solar. Solar power is an excellent choice for keeping batteries charged up under the right conditions. You’ll find few other than John who have bad experiences with this choice. A 1-Amp self-regulating promo item is a poor example for making a judgement on viability. Dismissing those who have had great success and satisfaction from their solar setups as basing their judgement on belief rather than fact is odd. In any event, PV panels DO require paying attention to their main requirement, which is full, unobstructed sunlight as much of the time as possible. If this is doable, then they will provide an impressively long lifetime of virtually maintenance-free and silent power, which does not consume any on-board resources. The panels are rated at ‘one sun’ from directly overhead, at 25C measured at the panel. This gives a laboratory standard useful for comparing panels, but does not reflect actual use conditions. For reference, our 3A panels actually produce from 1.5A to 2.8A when the sun is at its zenith – the variance due to season (SoCal). They are mounted flat on the roof. For winter use, or at northern latitudes, a tilting arrangement while camped would greatly improve the output. It would also add siting orientation as an important requirement, though. When camped in full sun – certainly not always possible – we have never run short of power with our setup. We use fans, lights, TV, VCP, etc, conservatively – but not obsessively so. We also have been careful to shift the power use away from the batteries as possible. E.g. most of our heating is with a small catalytic heater. No matter how vast your on-board resources, though, eventually you will need water, LP, or to dump. Balancing the battery-charging setup with these other constraints is certainly feasible for many with solar-power.sanyo solar pv panel

Response:

We have two siemens 100 watt panels and four trojan GC batteries. With the panels mounted flat we see about 30-35 amp hours a day into our batteries in arizona in the winter, about the same in montana in the summer. Tilting the panels in the summer has minimal benefit from our meter readings, about 25% more power in the winter by tilting. Long term solar seems to work, some friends are on their third or fourth RV with the same panels, most have swapped controllers along the way as the newer computerized ones give a better charge. We only have a 300 watt inverter to run the computer or the TV and can usually live comfortably on solar and get 3-4 hours of TV a night out of it. Once the batteries reach the trickle charge state you can directly use the excess power from the cells without drawing down the batteries. I watch the green light on the controller and when it comes on so does the computer! We are having some difficulty in deciding what to do regarding power needs while we are on the road and are hoping that you could share your experiences and ideas with us. Our goal is to live comfortable for a year with out running the generator all the time. Since we are a long ways off in the number of years before retirement our trip will be limited to about a year. At which time we will be selling the motorhome so resale value is a factor (it’s a 34′ 1991 Gulfstream). During our year we plan on mostly “boondocking” to keep expenses low, etc… At the same time we are gear nuts, TV, stereo, dvd movies, computer, etc, etc, etc… After adding up what I think our daily amp hr consumption might be I keep ending up with about 90 amp hrs daily.sanyo solar pv panel  The guy at the solar store seems to think this is a lot but it adds up when I use the charts.

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Response:

- Hide quoted text — Show quoted text -We are having some difficulty in deciding what to do regarding power needs while we are on the road and are hoping that you could share your experiences and ideas with us. Our goal is to live comfortable for a year with out running the generator all the time. Since we are a long ways off in the number of years before retirement our trip will be limited to about a year. At which time we will be selling the motorhome so resale value is a factor (it’s a 34′ 1991 Gulfstream). During our year we plan on mostly “boondocking” to keep expenses low, etc… At the same time we are gear nuts, TV, stereo, dvd movies, computer, etc, etc, etc… After adding up what I think our daily amp hr consumption might be I keep ending up with about 90 amp hrs daily. The guy at the solar store seems to think this is a lot but it adds up when I use the charts. Anyway here is a list of what we are looking at for our “system”. 2- AP 120 panels (14.2 amps/hr) at price of $650 each 1- Solaris 24 charge controller with battery temp sensing, $129 4- Trojan T-105 batteries $300 This system I’m told should yield around 80 amp hrs a day with 6 hours of good sunlight. So lets say that we start off with a  fully charged battery bank of 440 amp hrs and if I’m understanding correctly we never want to drain below 50% so we have 220 amp hrs to use. Lets say that we are using 90 amp hrs a day but putting back 80 through the solar panels, so really we are eating up the 220 held in the battery bank by going in the hole 10 amp hrs a day. Correct? 220 divided by 10 = 22 so with this line of thought we could go for 22 days before we needed to recharge with shore power or start up the generator. Is this thinking sound???? If so, it is surprising how much difference one vs.. two panels makes. one panel would yield around 40 amp hrs which would put us almost 50 amp hrs in the hole each day, which in turn would only allow a little over 4 days before the battery bank dropped below the magical 50% mark. Big difference! Like anything and everything we need to access the value of the second $650 panel to our lifestyle. But one question that may help is in regards to charging the battery bank back up with the generator. We have a Onan 5K watt generator. sanyo solar pv panel This among other things is where I’m still quite confused. Can you in fact charge the battery bank off the generator? If so how would you go about calculating the charge rate? Or maybe the easy answer I’m looking for is, an hour of generator time puts about  X amp hrs in to the battery bank. Would the inverter/charger apply to this scenario? The inverter/charger we are looking at is the Heart interface Freedom Combi 2000 watts, 12 DC volts, 120AC volts, 100A charge rate (off of shore power I’m assuming). We are also looking at the Link 1000 control panel to go with the inverter/charger. This is another area that has me confused (duh). The manual states the charge rate (3 step)  is at 14.2 volts for 1 hour then it drops to 13.2 volts for the float charge. How can I calculate the amount of time it would take to put, let’s say 200 amp hrs back into the battery bank? Any and all help is greatly appreciated. I’m always more comfortable hearing from people who have experience rather than take a salesman’s word for something. Thanks, JB

If the sun shines all day every day, no clouds, no rain, this might work, but there are two sides to the coin:  on hot days, no AC, on rainy days no hot water unless you’re on propane, altogether a step up from camping, but not very high up.  I boondock quite often, run the genset for heavy duty stuff, and the 2500 Heart for ‘most everything else.sanyo solar pv panel  It works for me, because I went from philosophical to practical to pragmatic as soon as I hit the road.

Response:

- Hide quoted text — Show quoted text – If you’re going to drag a toad around, there is another very satisfactory option.  Put half your house batteries in your toad. When you drive the toad, the battery is charged by the toad’s alternator.  When you return to the RV, you plug the toad’s house battery into the RV using an Anderson connector (aka “forklift battery connector”) and some welding cable.  When the toad is being towed, the Anderson connector is plugged in to keep the toad’s house battery charged.  An added benefit is that you’ll never be out in the toad with a dead battery!  Another nifty thing is, once you have the Anderson connector installed, jumper cables consist of little more than another Anderson connector, a bit of cable and a couple of clips.  Handy when you need to boost someone ELSE, of course sanyo solar pv panel  You can buy the Anderson Connectors from Waytek Inc, 800 328-2724. Just an observation here.. in the next paragraph you cite your reasoning for not having a multi-tude of batteries in your coach.. possible fire hazard and weight (possibly reducing mileage) …  Well I don’t know where you intend to put these extra coach batteries in the tow but it looks like to me more wiring means more chance for electrical problems.

Separating the house battery into two banks has absolutely nothing to do with how big the battery is.  If I pulled a toad, I’d put one battery in the toad and one in the motorhome.  Still have my 300 amp-hours, only split across two vehicles.  In all my 4 wheel vehicles, the batteries are all located in the trunks where I moved them to.  Yields better handling, longer life from the more benign environment and frees up a hole in the engine compartment where a couple of quarts of oil or whatnot can be stored.  Plus I can use a big honking (technical term) deep discharge battery that wouldn’t fit in the engine compartment. If I had a toad, the house battery would go right beside the cranking battery in the trunk.  If the wiring is done correctly, that is, the battery in a sealed battery box with the cables taken directly through the trunk floor and run along the frame rails or ribs, then there is nothing in the vicinity of the wiring or battery to burn even if a short occurs.  Compare that to the (often lack of) “battery boxes” in many RVs. It ain’t gonna make much difference in the weight department. The combo weight is going to be the same  (motor-home and tow).

But the weight’s in the toad, riding on the toad’s tires which likely offer less rolling resistance than the MH’s truck tires.  If the MH is at its GVW as mine is, that could make some difference.   The largest benefit, of course, remains that the house battery can be charged while the toad is driven. sanyo solar pv panel  Gary One other comment before I go.  Though a lot of people put huge batteries in their RVs, I’m uncomfortable with that configuration for a number of reasons.  The primary concern is the fire hazard. Having hundreds of amp-hours of battery capacity sitting there just one short circuit away is a recipe for a bad and persistent fire, as Bob Evans reported here a couple of weeks ago.  A big battery can keep a shorted wire glowing hot enough to kindle fire for a long  time regardless of how much water or extinguishing agent you pour on it.  Yes, proper fusing and wiring can mitigate the risk but if I can do the job without all that potential energy sitting there, so much the better.  The other consideration is weight.  Perhaps more so for me than you because my rig is at its weight limit now.  But even if the rig can handle the weight, it decreases mileage, increases the rate of tire wear and impairs the performance of the vehicle.  The effects are perhaps small, but if I can do the job without the weight, wsanyo solar pv panel .  Well I don’t know where you intend to put these extra coach batteries in the tow but it looks like to me more wiring means more chance for electrical problems.  It ain’t gonna make much difference in the weight department. The combo weight is going to be the same  (motor-home and tow). Just my view… Gary One other comment before I go.  Though a lot of people put huge batteries in their RVs, I’m uncomfortable with that configuration for a number of reasons.  The primary concern is the fire hazard. Having hundreds of amp-hours of battery capacity sitting there just one short circuit away is a recipe for a bad and persistent fire, as Bob Evans reported here a couple of weeks ago.  A big battery can keep a shorted wire glowing hot enough to kindle fire for a long

time regardless of how much water or extinguishing agent you pour on – Hide quoted text — Show quoted text – it.  Yes, proper fusing and wiring can mitigate the risk but if I can do the job without all that potential energy sitting there, so much the better.  The other consideration is weight.  Perhaps more so for me than you because my rig is at its weight limit now.  But even if the rig can handle the weight, it decreases mileage, increases the rate of tire wear and impairs the performance of the vehicle.  The effects are perhaps small, but if I can do the job without the weight, why not?sanyo solar pv panel

Dave There was an article some time ago in FMCA magazine (years ago) about a gentleman who set up a solar array on his motorhome.. He spent extended time in AZ in the winter as I remember.. He used solar and wind.  He had all the info about what it cost and how much it produced.  It was “real life” as opposed to some of the opinions expressed here.. His goal was to be self-sufficient electrically… He was learning as he went.. GRIN.. One thing is that in his case it appeared that most of the figures he got from the solar sales people were not really accurate… It appears that they tend to under-estimate the needs of a rv.. He lists all items in his rig. (ice-maker,puter,stereo, etc )   up till the last article he wrote he was not self -sufficient yet but very close.. This setup for me would not be real practical as I don’t set still more than a day or two.. Our rig is all electric and I don’t think that we could ever install enough panels unless we hooked up a trailer.. (GRIN)… As far as solar or wind power are concerned, a good alternative source of power.. It may not pay for itself in the near term, but like you said, the panels are not likely to wear out.. I have a friend in Montana that has a PV array on his home. Without going into much detail, he figures a payback in 11.3 years at today’s energy cost, quicker if the rates go up and I suppose longer if they go down.. Then he will just be selling power to the power grid. (which he does now when he gets things fully charged) There is one poster that runs on like he knows quite a bit on just about everything, but don’t believe all you read.. He has been proven wrong in many cases and in one case the consequences could be very electrifying or the arcing could start a fire and according to the NEC not even legal in dwellings to be occupied… I like to call them “jack of all trades, master of none” …  He isn’t always wrong and does have some very good posts… Just my opinion…sanyo solar pv panel

- Hide quoted text — Show quoted text – Good questions.  I await more learned answers than I can give (and I don’t have my solar books here).  But I already have bought 3 K120’s and plan a similar system to yours.  3 versus 2 panels, as it gives much more solar charging and I hope to not have to use a generator except in a real sunless spell. Consider that the panels are good for 25 or more years as they never wear out.  So they are like gold almost and should have a good resale value, separate from the MH. sanyo solar pv panel

Response:

- Hide quoted text — Show quoted text – First, my bias.  I am biased heavily against solar.  I went through the solar stage back in the 70s.  It was impractical back then for anyone other than the stary-eyed zealots.  The only thing that has changed is that the current crop of panels are a bit more efficient.  Not enough difference to overcome all the other practical problems.  One of the biggest problems you’ll run into is that much of what you hear or read about solar is more wistful pining than fact.  The reason is solar is the darling of the environmental wing where most things are based on beliefs rather than fact. <snip the rest of the hot air on solar.

Let’s see if it is hot air. Solar power is an excellent choice for keeping batteries charged up under the right conditions. You’ll find few other than John who have bad experiences with this choice. A 1-Amp self-regulating promo item is a poor example for making a judgement on viability. Dismissing those who have had great success and satisfaction from their solar setups as basing their judgement on belief rather than fact is odd.

Self-regulating promo?  WTF?  I used my battery maintainer (a device almost 3 ft long by 18″ wide and fully regulated via an external shunt regulator – hardly a toy.) as a convenient example because that is the only panel I now own, not being fool enough to get burned on solar twice.  I tried to go self-sufficient back in the 70s when government subsidy money flowed in great rivers.  I was not willing to adopt an austere lifestyle and thus found the concept impractical even though I literally had a roof full of panels. In any event, PV panels DO require paying attention to their main requirement, which is full, unobstructed sunlight as much of the time as possible. If this is doable, then they will provide an impressively long lifetime of virtually maintenance-free and silent power, which does not consume any on-board resources. The panels are rated at ‘one sun’ from directly overhead, at 25C measured at the panel. This gives a laboratory standard useful for comparing panels, but does not reflect actual use conditions. For reference, our 3A panels actually produce from 1.5A to 2.8A when the sun is at its zenith – the variance due to season (SoCal). They are mounted flat on the roof. For winter use, or at northern latitudes, a tilting arrangement while camped would greatly improve the output. It would also add siting orientation as an important requirement, sanyo solar pv panel

Ah, now we get to the crux of the problem – another one of those SoCal types who forgets that the rest of the world isn’t like SoCal.  The graphic at http://www.etaengineering.com/resources/insolus.html graphically illustrates the irrelevance of SoCal results to the rest of the country.  This graphic shows that SoCal gets nearly the highest solar influx of any area in the US.  SoCal gets over 3 times the amount of solar energy as New England and over twice as much as we get here. Let’s do some calcs using the figures from the above illustration. At http://www.eren.doe.gov/power/pdfs/pv_concentrators.pdf there is an interesting DOE report on the state of the art on utility-grade PVs.  In the tables, it is noted that the state of the art PVs are capable of 23% conversion efficiency when unaided by any concentrator.  Consumer cells aren’t as good so let’s round to 20% Here in Tennessee, we get an AVERAGE of 3000 watt-hours per square meter per day.  Tossing away 80% of that, there is 600 watt-hours/sq meter/day available.  At 12 volts, that would be 50 amp-hours/sq meter/day.  Scanning the net, it appears that PV panels run 600-800 dollars per sq meter.  That’s pretty expensive electricity. More importantly, it’s not much electricity at all.   It is important to note that the figures in the above illustration are computed for a surface optimally aimed at the sun.  If the panel is laying flat, the the output is reduced by the cosine of the angle between optimal and flat.  It is also important to note that those numbers are AVERAGE.  The daily variance from average is large. Here in Tennessee, where one can go for a week at a time with heavy overcast, the average doesn’t matter much when your batteries are flat. Steve, glad that solar works for you in the SoCal desert. Fortunately for the rest of us, the rest of the US has slightly more varied and interesting terrain.  Unfortunately (at least for the solar proponents), the available solar energy varies at least as much. Hmm, looks like the hot air is cooling rapidly….sanyo solar pv panel

Response:

We are having some difficulty in deciding what to do regarding power needs while we are on the road and are hoping that you could share your experiences and ideas with us. Our goal is to live comfortable for a year with out running the generator all the time.

First, my bias.  I am biased heavily against solar.  I went through the solar stage back in the 70s.  It was impractical back then for anyone other than the stary-eyed zealots.  The only thing that has changed is that the current crop of panels are a bit more efficient.  Not enough difference to overcome all the other practical problems.  One of the biggest problems you’ll run into is that much of what you hear or read about solar is more wistful pining than fact.  The reason is solar is the darling of the environmental wing where most things are based on beliefs rather than fact.  I’ll outline some examples as we go. I’m going to assume that you really mean that you want to be comfortable in your travels.  To me, comfort includes not having to worry about every amp-hour (or every ounce of water or propane, for that matter.)  It also includes being hassle-free.  Now if you LIKE futzing around with your power system to keep it working well during your travels, then your definition of comfort may be different than mine. – Hide quoted text — Show quoted text – Since we are a long ways off in the number of years before retirement our trip will be limited to about a year. At which time we will be selling the motorhome so resale value is a factor (it’s a 34′ 1991 Gulfstream). During our year we plan on mostly “boondocking” to keep expenses low, etc… At the same time we are gear nuts, TV, stereo, dvd movies, computer, etc, etc, etc… After adding up what I think our daily amp hr consumption might be I keep ending up with about 90 amp hrs daily. The guy at the solar store seems to think this is a lot but it adds up when I use the charts. Anyway here is a list of what we are looking at for our “system”. 2- AP 120 panels (14.2 amps/hr) at price of $650 each 1- Solaris 24 charge controller with battery temp sensing, $129 4- Trojan T-105 batteries $300 This system I’m told should yield around 80 amp hrs a day with 6 hours of good sunlight. So lets say that we start off with a  fully charged battery bank of 440 amp hrs and if I’m understanding correctly we never want to drain below 50% so we have 220 amp hrs to use. Lets say that we are using 90 amp hrs a day but putting back 80 through the solar panels, so really we are eating up the 220 held in the battery bank by going in the hole 10 amp hrs a day. Correct? 220 divided by 10 = 22 so with this line of thought we could go for 22 days before we needed to recharge with shore power or start up the generator. Is this thinking sound???? If so, it is surprising how much difference one vs.. two panels makes. one panel would yield around 40 amp hrs which would put us almost 50 amp hrs in the hole each day, which in turn would only allow a little over 4 days before the battery bank dropped below the magical 50% mark. Big difference!

OK, here’s the first series of solar myths and problems.  The first thing you have to do is look at what the specs really mean.  Solar panel specs tend to be wildly optimistic.  For example, I have an Arco (now Siemens) panel I used to keep the battery charged on one of my catering trucks (I own a restaurant, among other things.)  It volts.  In reality it produces about 20 volts open circuited but when an amp is drawn, it loads down to about 13 volts. This panel will indeed produce an amp of current – in the summer noon-day sun with the panel angled optimally toward the south.  On a cloudy winter day with the panel laying flat on the roof of the truck, it makes only about 100 ma.  In the winter with the sun low on the horizon all day, even on a cloudless day, it’s production is less than 400 ma.  Yes, it could do a bit better if the panel was angled toward the sun but then we’re back to daily futzing again.   Let’s take a look at the math.  (If you go to http://www.altonet.com/~solarpv/01index.htm and download the Acrobat catalog file, you’ll find a design guide that has a lot more details than this post.)  You calculate the amp-hours by multiplying the amps the solar panel supplies times the hours of illumination.  In your example above, you assume that you will achieve almost the peak output for 6 hours a day.  This might be true in the summer in the south but it will NOT be possible any other time and in any other location.  Based on my measurements here in Tennessee, I’d probably cut that by at least a third for an annual average.  Even more when evaluating a short period of time, say, the month of January with the panels laying flat on the roof of the RV. The next problem you have is that you assume the entire power output of the panel goes to charging the batteries.  This is not the case. Up to 10% of the charging current is dissipated as heat in the battery and does not contribute to the charge.  You must take that into account when you’re figuring out how much usable energy will be deposited in the battery by the solar panels. There is one error in your model that helps you.  That is, assuming only a 50% discharge.sanyo solar pv panel   This is a popular myth in this newsgroup but there is no basis for it, particularly for the Trojan batteries you plan to buy.  If you go to http://www.trojanbattery.com/technical%20assist/faqs/charging.htm, you will find the following text: “Trojan’s deep cycle lead acid batteries can be cycled to any percentage of their rated capacity and then be recharged. However, Trojan does recommend that you never cycle below 80% of the battery

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