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Old 12-06-2010, 03:34 PM   #155
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MPPT & other magical things


My writings came out of frustration after looking at dozens of RV solar systems (most of which that did not work) and talking to every solar dealer I could find. I am not making any of this up.

I am trying very hard to explain this without preaching, but it is not easy. This is why I started writing and gave up trying to reason with the general consensus, who had it all wrong. Trying to reason with people who have been agreeing with each other for years, even when they had been wrong all the while, was a losing battle.

I once had a guy with several panels all wired in series, producing very high voltage and very little amps point to the remote that came with the most expensive controller he could buy, show me the amps going in, the amps coming out and exclaim "look at all that boost". (Over 300%) That is the very definition of a fool. Of course the amps going out at 14V was much higher than the amps going in at over 70V. However, is that "boost"? No, it is not. I measured the input voltage & amperage, multiplied them to get watts and then did the same on the output side. There was a 10% loss!! Why? Because it was cloudy and those MPPT controllers are not efficient when at lower power during cloudy conditions. By the way, I have repeated this test with the same outcome for two different brands of controllers. So, those of you who tell me about the boost you are getting when it is cloudy need to wake up and do some thinking. If it looks too good to be true, it probably is. A third brand, the Morningstar Tristar MPPT is the best one that I have tested, but even it is not as efficient as the regular PWM Tristar. It is impossible to add electronics without having it soak up some energy. However, I believe in it enough that I have bought one for the system on my own house. So much for those of you who keep repeating that I don't like MPPT.

In order to know what boost you may or may not be getting you need to consider what a set of standard voltage panels parallel connected would give you in amps at the batteries when supplied through a good PWM controller (not one of those shiny flush mounted RV things). Then compare the amps you are getting out of the same number of watts with whatever voltage panels you are running. This is not something that is easy to do. I have done just this by experimenting with different controllers on the same system. Not something that a guy who is trying to sell you something with outrageous claims is likely to be honest about. He wants you to blindly believe what you see on his meter.

The guy who sells the 22V panels likes to make ridiculous claims of boost, talking only about amps, hoping that people are not smart enough to realize that a 100 watt panel cannot supply more than 100 watts and that the same money can buy 130 watt panels elsewhere. Those bigger panels will supply more WATTS into the batteries if connected with big wires and a good PWM non boosting controller. If you want to spend the money for a good MPPT controller (not one of those "budget" units), you can increase the watts a bit during cool & low battery conditions. Is it worth the money? On systems over about 600 watts, yes. On large systems using very high voltage panels so that you can use smaller wires due to less voltage drop? Yes. On two panel RV systems? Absolutely not.

Last; if you want to buy MPPT go right ahead and do so. However, read the specs and the directions. You should follow the voltage drop recommendations and use bigger wire when installing MPPT, not smaller. You need the volts to get to the controller in order for MPPT to work. The RV solar dealers who are ignoring the voltage drop and claiming that MPPT makes up for it are lying to you.
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Old 12-07-2010, 11:03 AM   #156
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Bob does now what he is taking about.

Quote:
Originally Posted by SCVJeff View Post
He clearly doesn't know what he's talking about
To Jeff,

The lack of common sense in this world is astounding. You and people like you are the reason I gave up on these forums in the past. Just because I spend great efforts trying to explain things for the majority and do not get technical enough to satisfy you and other over technical types does not mean that I am wrong. There are many people with systems now working who will tell you that I am right. I have spent hundreds of hours helping people for free, so for you to suggest that I have an agenda is ludicrous.

I spent years figuring out that the RV solar dealers, the RV suppliers and the majority of the RV Owners with solar on their rigs didn't know what they were talking about. Look around and you will still see those rigs everywhere. Guys with red generators behind rigs covered with solar panels. Others with more panels than anybody needs, plus a wind generator spinning on a sunny day, when the solar power should be shutting it off. People who start their generator when a few clouds go over, because their systems do not work, no matter how many solar panels they have on the roof. Look around on these forums and you will still see people talking about how solar power just doesn't work. I saw a post just the other day by somebody who said that people with solar panels in the LTVA's go to bed early and can't watch TV. One of our friends, who knows better, told my wife last year that he couldn't believe that she was sewing & ironing her quilt squares on a cloudy day, while he was standing in our rig and watching her do so. That is what I fight. I looked at dozens of rigs and talked to all of the dealers back when I was trying to figure this out and I had to figure it out for myself. The lack of knowledge in the past and now the lack of honesty and business ethics on the part of most of those dealers is appalling. I said "most", not all. I have to repeat myself, since I know you don't read very well.

Perhaps your system works and you are welcome to have spent any amount of money on any equipment sold by any outfit making ridiculous claims that THEY cannot back up. Show me the third party testing. But do not tell me, the guy with ten year old panels, who still doesn't own a generator and who successfully runs his life including power tools and my wife's electric iron with a small system with no expensive MPPT controller, or an inverter charger, that I don't know what I am talking about. AND, do not go around telling people that they have to buy those expensive & over marketed things in order to be successful with solar power. It makes you look like you work for one of those dealers. I really wonder.

Watch... This will get deleted.
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Old 12-07-2010, 11:53 AM   #157
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Very informative discussion about solar power. My plan is to also get a solar set up to be grid free and full time. Its way past time to get started on adventures with my better half and 4 dogs 6 puppies {three papered females and three maltese/yorkie males.
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Old 12-08-2010, 08:07 AM   #158
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Old 12-10-2010, 07:58 AM   #159
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I followed HB suggestions and our solar system is great. 400 watts of solar runs pretty much everything. Even though we have a generator....we rarely use it anymore unless we have to run the rooftop AC units.

We had 10 people in our RV at the recent Big XII championship game and with people going in and out and flushing the toilet, watching TV, etc....never drew below 85%. Amazing. My uncle is a licensed electrician and he was pretty amazed by the whole set up.

Thanks Handy Bob....keep spreading the word. You now have a few 'disciples' too!
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Old 12-10-2010, 09:08 PM   #160
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I've been lurking in this thread since I got "slapped" down for trying to explain why HB's advice works.

If you look deep enough into what he says, you can tease out the truth. However, you will have to endure his rants and his bellowing of "I am right" and "they are wrong".

So, in the end, big wires, to the controller (less important, I can go into intimate detail of why), big wires to the battery. Controller as close to the battery as possible. Monitor your usage with a trimetric (or equiv.) and size your system to match. Temperature compensation of the charge voltage, and finally, raise the bulk charge termination voltage to 14.8V.

Yeah, your system will work, but you won't know why, or what made the difference.

I've talked to the battery charger experts that I work with...I've studied the -science- behind all this. Most of what HB says about solar power is true...but there are some basic assumptions that he's made about a PV system that aren't exactly right. They aren't significant to the function of his system, but they could be to yours...

To summarize, I'm not being critical of HB, nor am I saying he's wrong...what I AM saying is that you have to be aware of the science behind the statements and claims that are made about PV systems...when you have that, you can't be fleeced.
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Old 12-12-2010, 07:37 PM   #161
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Yeah, your system will work, but you won't know why, or what made the difference.

To quote my wife: " You don't have to know how to build a sewing machine to make a beautiful quilt and you don't have to know how to manufacture paint to paint your house." You really should see the beautiful solar quilts she makes without having a clue how her machine works. Amazing!

When you obsess about the wrong things, and listen to people who think they know but don't, you will throw your money away. For instance, do you yet know that SpursMPV listened to bad advice here and moved his meter closer to the batteries and didn't install it where it should have gone because somebody was telling him that he had to worry about voltage drop? There are four wires connecting that Trimetric. Two power the meter. The other two are signal wires that carry zero current and voltage drop is not an issue, so if you just read the directions instead of trying to reinvent the wheel, you can make your life a lot easier. The solar dealers in Quartzsite refuse to read the directions. They also will not sell you a Trimetric because if they did, you would know that what they sold you does not work. They have been in business for years and they know better. "Nobody needs #4 wire!" Good luck!
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Old 12-12-2010, 08:14 PM   #162
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You don't have to know how to build a sewing machine to make a beautiful quilt...
Nor do you need a sewing machine at all...but if you choose to buy a sewing machine, knowing about them becomes quite useful. If you know nothing about sewing machines, how can you prevent the dealer selling you half the machine you need for 10x the price?

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When you obsess about the wrong things, and listen to people who think they know but don't, you will throw your money away.
Without understanding, how are you to know who to listen too? No disrespect HB, but how do I know that YOU know what you are talking about? For all I know, you are blowing smoke about your system...I don't believe that, but I don't know you any better than I know the dealers.

The only way I can discern if a person is knowledgeable about a subject is to have knowledge about that subject. How am I to know if 4 gauge wire is suitable, or if I should have 0000? Why use a trimetric vs a Xantrex Link system? or why use MorningStar controller, a BlueSky controller, a PWM or a MPPT, or even a relay on/off system? If I listen to the dealer, how do I know I can trust him? Likewise for the others that want to pass on their knowledge?

Fundamentally, it's like I told my doctor, nobody cares about my health as much as I do. I don't care if you can watch TV, iron clothing, use the microwave and run your lights...what I care about is if *I* can do those things with the system I have.

In the end, the only way to prevent someone from pulling the wool over your eyes is to know the subject...
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Old 12-12-2010, 09:11 PM   #163
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In the end, the only way to prevent someone from pulling the wool over your eyes is to know the subject...
I would say thats what everyone on this thread is trying to find out a exchange of views so we can make the right decisions when we put system together.
I think after reading this long thread there is a great deal to learn about solar systems and I would take everyones advise and work from members comments.
If you all keep to the subject matter and not between individuals it will continue to be a learning experience for everyone.
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Old 12-13-2010, 01:48 PM   #164
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HB and RD
I want to know why something works or does not. As an example we need to have basement work done to stabilize a wall that is in the process of failure. Four companies two totally not listening to me (I have done concrete inspection) and two that proposed fixing what I know to be the problem with two separate methods. The next step will be talking with an engineer to see which will be the best solution.
I did not do my homework with the solar panel and it has cost me, and if I had not be knowledgeable about concrete I might have bought a solution that did not in reality address the problem correctly.
If I had the "why this" for solar I would not have bought a panel meant for a residential/grid tie system that put out more voltage than my PMW controller was capable of handling.
Therefore HB, patience with those of us that do read instruction manuals and really want to understand why what you do works.
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Old 12-14-2010, 03:01 AM   #165
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Well - I have read heaps (but not all) of this thread, and I have invested in 4 12V gel 100AH batteries, with two 80W solar panels to recharge them. I have another lead-acid battery of about 80AH also in parallel, but at the front of the bus, not underneath like the others. Is there likely to be any problem with charging the lead-acid with the gel batteries? I have heard that the gel batteries do not like too much voltage to recharge them, but wet batteries thrive on higher voltage. Right?

I have had a new battery cage added, and have room for another 12v gel battery if required. Seems to be no reason why not, it is just like having a pool that is a couple of inches deeper - more storage, and the same evaporation, so same need for refilling, as I see it. I can add more solar panels if required, but the sun here in NZ is pretty potent and we are getting way more volts than the manufacturer claims due to the depleted ozone layer over us. (Thanks for helping with global warming by the way, lol.) I am running two radios, a fridge (gas/electric duo) and a satelite dish, a DVD player and a couple of TV's. Don't need aircon (yet?) - we can just open a window. Electric blanket and gas heating can wait for about six months (summer here), so I am about to see if it all works without intervention from the generator or shore power. As I see it, the only thing I need to check is the size of the wire from the solar to the controller?

Will keep you all posted. Thanks for the information - hope I have read it properly.
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Old 12-14-2010, 03:23 PM   #166
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Well - I have read heaps (but not all) of this thread, and I have invested in 4 12V gel 100AH batteries, with two 80W solar panels to recharge them. I have another lead-acid battery of about 80AH also in parallel, but at the front of the bus, not underneath like the others. Is there likely to be any problem with charging the lead-acid with the gel batteries? I have heard that the gel batteries do not like too much voltage to recharge them, but wet batteries thrive on higher voltage. Right?

I have had a new battery cage added, and have room for another 12v gel battery if required. Seems to be no reason why not, it is just like having a pool that is a couple of inches deeper - more storage, and the same evaporation, so same need for refilling, as I see it. I can add more solar panels if required, but the sun here in NZ is pretty potent and we are getting way more volts than the manufacturer claims due to the depleted ozone layer over us. (Thanks for helping with global warming by the way, lol.) I am running two radios, a fridge (gas/electric duo) and a satelite dish, a DVD player and a couple of TV's. Don't need aircon (yet?) - we can just open a window. Electric blanket and gas heating can wait for about six months (summer here), so I am about to see if it all works without intervention from the generator or shore power. As I see it, the only thing I need to check is the size of the wire from the solar to the controller?

Will keep you all posted. Thanks for the information - hope I have read it properly.

First things first. You definitely don't want to hook your lead acid in parallel with your gel. Not only do they have different charging profiles, they have different capacities. It's like trying to fill a 10 liter bucket and a 5 liter one from a single hose over the same amount of time. One will always fill sooner than the other. when that happens, the current is reduced and the emptier battery won't be filled. (Unless you have separate charging circuits for each).

Not only should you have the same amp hour rating for each battery in parallel, when possible have the same model from the same mnfctr. This is the best way to a balanced pack. Definitely make sure the size of the wire is adequate for VOLTAGE DROP, not just MAXIMUM CURRENT. YOU want to size the dc wiring for 5% loss or lower. There are charts that you can google that will size it for you. Just know your max amps and total length of wire to and from the battery pack.


While I am a big fan of more storage, With a limited budget, I'd opt for more solar first... especially with the electrical draw you have. 160 watts translates into about 8.5 to 9 amps per hour of charging. My guess is, that barely keeps up with your average 24-hourly use with TV's, satellite, radio, basic lighting, etc. Now, this assumes you are boondocking mostly, not running a charging generator or alternator charge daily. Plus, you have to factor in cloudy days and less insolation in winter.

As a full-time boondocker living off solar mostly, with some wind, believe me you need more charging capacity than you think. And your batteries should end the solar day fully charged. If they daily only get partially recharged they will quickly sulfate and your money will be wasted. Remember, your charging capacity is more than just what you are using at the moment, it has to include everything you used when the sun wasn;t shining, plus extra for charging inefficiencies.

Hope that helps.
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Old 12-14-2010, 09:50 PM   #167
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First, my purpose in installing solar on my RV was to enable me to keep using as many of my creature comforts as possible while I'm off the grid.

If I wanted to rough it, conserve, and save resources, I'd sell the RV and buy a tent. In fact if there was a Mr Fusion for RVs, I'd install it. However, though I backpacked the Rockies with the Mrs. about 40 years ago, our backs are no longer up to that.

Those of you who can live off less, more power to you (no pun intended). But that's not for me.

Second, IMHO if you do a lot of camping in the shade, buy a generator. From solar power records stored in my charge controller, I found that light/moderate shade derated my PV array by 10-30% and heavy shade 50-90%. Even with a large system (mine was 760W), that sort of depletion kills many creature comforts.

The first system I installed was a 240W, two panel system with a Blue Sky Solar Boost 2000 (20W) controller connected to two Trojan T105s. It was a great system for battery charging while our RV sat in outdoor storage.

However, I wanted more juice so I added 4 more Kyocera panels (130W), a Xantrex 60W MPPT controller, a Xantrex 2000W pure sine inverter/charger, and replaced my two Trojans with four Lifeline AGMs.

I opted for serial/parallel PV array wiring because my first wiring choice -- parallel for maximum shade tolerance -- drew far too much current (75 amps). The wiring was sized for 3% line loss. Though it was a sweet system, I'm a part timer who camps mostly in partly to heavily shaded areas so luckily I had generator backup.

On my new RV I'm going to start with a small battery maintenance system like before, but allow for expansion if I go that route again.

Here's my install:
MobileMe Gallery

Several sites I found useful:

Blue Sky Tech Bulletins:
Blue Sky Energy Inc. | Technical Bulletins

Apollo Solar T80 Controller Manual (Good planning advice + these guys use a 1.5% line loss):
Charge Controllers

MidNite Solar (great general info + combiner box breakers):
MidNite Solar - Renewable Energy System Electrical Components and E-Panels.

Alt-E Store (handy wire sizing with adjustable line loss):
How to Size Wiring and Cabling for Your System - AltE

California PV Ratings ("real world" PV values):
List of Eligible SB1 Guidelines Compliant Photovoltaic Modules - Go Solar California
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Old 12-15-2010, 12:55 AM   #168
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