looking for a cheap charge controller for a single 100w panel

[akrvbob]

Okay let's look at the science and the science doesn,t change if it's a 100 watt panel, four 100 watt panels or one 315 watt panel. It's always the same. Taken from the Northern Az Wind and Sun website:

http://www.solar-electric.com/mppt-solar-charge-controllers.html/

I couldn't control the fonts in the cut and paste. But in the red text below they take the example of a 130 watt panel that might be losing 48 watts of power because the battery is at 10.5 volts and the panel is putting out 18 volts. With a PWM controller you've just lost 7.5 volts of power

If you are satisfied with that performance, then a PWM controller is perfect for you. I'm not. I bought 130 watts and I want 130 watts to go into my battery, not 82.

Below that is another quote from that page where they describe when a MPPT controller offers it's most advantages. They say it offers the most advantages in winter with it's cool weather and low sun, under cloudy skies and when the battery is very low. All times when we need the most power we can get and that's when a MPPT works the best. 

Below that is a description of what MPPT does to get 20-45% more power into your battery in the winter.

= = = = = = = = = = = = = = = = = = =

[font=helvetica, arial, sans-serif]So what do you mean by "optimize"?[/font]
[font=Arial, Helvetica, sans-serif]Solar cells are neat things. Unfortunately, they are not very smart. Neither are batteries - in fact batteries are downright stupid. Most PV panels are built to put out a nominal 12 volts. The catch is "nominal". In actual fact, almost all "12 volt" solar panels are designed to put out from 16 to 18 volts. The problem is that a nominal 12 volt battery is pretty close to an actual 12 volts - 10.5 to 12.7 volts, depending on state of charge. Under charge, most batteries want from around 13.2 to 14.4 volts to fully charge - quite a bit different than what most panels are designed to put out.[/font]
[font=Arial, Helvetica, sans-serif]OK, so now we have this neat 130 watt solar panel. Catch #1 is that it is rated at 130 watts at a particular voltage and current. The Kyocera KC-130 is rated at 7.39 amps at 17.6 volts. (7.39 amps times 17.6 volts = 130 watts).[/font]
[font=helvetica, arial, sans-serif]Now the Catch 22[/font]
[font=helvetica, arial, sans-serif]Why 130 Watts does NOT equal 130 watts[/font]
[font=helvetica, arial, sans-serif]Where did my Watts go?[/font]
[font=Arial, Helvetica, sans-serif]So what happens when you hook up this 130 watt panel to your battery through a regular charge controller?[/font]
[font=helvetica, arial, sans-serif]Unfortunately, what happens is not 130 watts.[/font]
[font=Arial, Helvetica, sans-serif]Your panel puts out 7.4 amps. Your battery is setting at 12 volts under charge: 7.4 amps times 12 volts = 88.8 watts. You lost over 41 watts - but you paid for 130. That 41 watts is not going anywhere, it just is not being produced because there is a poor match between the panel and the battery. With a very low battery, say 10.5 volts, it's even worse - you could be losing as much as 35% (11 volts x 7.4 amps = 81.4 watts. You lost about 48 watts.[/font]

[font=Arial, Helvetica, sans-serif]==========================[/font]

[font=Arial, Helvetica, sans-serif][size=small][font=Arial, Helvetica, sans-serif]MPPT's are most effective under these conditions:[/font]
[/font][/size]
[size=small][font=Arial, Helvetica, sans-serif]Winter, and/or cloudy or hazy days - when the extra power is needed the most.[/font][/size]

• Cold weather - solar panels work better at cold temperatures, but without a MPPT you are losing most of that. Cold weather is most likely in winter - the time when sun hours are low and you need the power to recharge batteries the most.
  
• Low battery charge - the lower the state of charge in your battery, the more current a MPPT puts into them - another time when the extra power is needed the most. You can have both of these conditions at the same time.
  
• Long wire runs - If you are charging a 12 volt battery, and your panels are 100 feet away, the voltage drop and power loss can be considerable unless you use very large wire. That can be very expensive. But if you have four 12 volt panels wired in series for 48 volts, the power loss is much less, and the controller will convert that high voltage to 12 volts at the battery. That also means that if you have a high voltage panel setup feeding the controller, you can use much smaller wire.

= = = = == = = = = = = = = = = = = = = = = =

[font=Arial, Helvetica, sans-serif]Maximum Power Point Tracking is electronic tracking - usually digital. The charge controller looks at the output of the panels, and compares it to the battery voltage. It then figures out what is the best power that the panel can put out to charge the battery. It takes this and converts it to best voltage to get maximum AMPS into the battery. (Remember, it is Amps into the battery that counts). Most modern MPPT's are around 93-97% efficient in the conversion. You typically get a 20 to 45% power gain in winter and 10-15% in summer. Actual gain can vary widely depending weather, temperature, battery state of charge, and other factors.[/font]

 

[jimindenver]

Morningstar controllers are not American made.

I have used a Chinese made MPPT controller for 3 years with out fail. You can pick them up for $85 with free shipping. They have developed a following and are known to do what they say they will. Side by side they milk every bit as much power out of a 250w GT panel as my Morningstar TS-MPPT-60 does.

Rely on the experts? Writing a blog does not make one a expert. Setting up and using a single system successfully doesn't either. I've been in PV for years, built and ran three systems, tested four different panels of two different types in every possible conditions on two different controllers. Done things the experts said could never happen even though they had never tried. Were I to have kept it all in a blog this conversation may have been about me and not Handy Bob.

Things the experts have been wrong on

Mono vs poly. General knowledge, advertising and hype say that mono's are so much better than polys. My first mono vs poly test showed the mono noticeably smaller in foot print, put out less in bright light and was useless in overcast situations while the poly dropped according to how thick the overcast was. I was told I was wrong, my mono panel was faulty, I didn't understand, all the test show.....

The next year I picked up two 245w mono's and used them for a year. They would drop from 17a each to 2.38a as soon as the clouds rolled in. I knew my 230w poly could do 5a in pea soup so I started looking for the mono's replacements. The three 250w polys will do up to 25a in heavy overcast and that will keep us going.

When I first started I noticed that once the battery was in float that I could turn on everything in the trailer and the battery wouldn't lose voltage, the system was running those things directly. I could see the amps produced rise and fall as buttons were pushed.  No no I was told by the experts. Battery runs things and the solar charges the batteries. I said but wait the battery is in float and unchanging in voltage. They said it happened so fast you can't see it on a meter or controller display. So I took a panel, controller, battery, inverter and load, got it all running and pulled put the battery. Load kept running and so ended that conversation with the experts.

When I decided to take the concept farther and run a small air conditioner in the rare instance we need it, I was laughed at. Even after I set it up and tested I was told it wouldn't work. How funny it is now that I can run the little A/C from 10 am to 3 pm and still toss the batteries a bone while it runs. Before and after it does pull small amounts from the battery but when the compressor cycles, the batteries catch up.

As for the advantage of a smaller MPPT system. A Eco-worthy 20 amp MPPT, a inexpensive GT poly panel and the same wiring, etc you would need for a PWM system can come in under $500, be easier to mount and provide more power than a 12v system costing the same. A number of people copied my original system of a 230-250w GT panel with the Eco-w, I never told them they should, they just liked my results.

Then again, I'm no expert, I just design systems that do things the experts say can't be done.

 

[ccbreder]

And here I always thought any charge controller fed about 14 volts to the battery and then the state of charge of the battery determined the amps flowing from the controller. 7.5 x 14. Oh sorry, the original question was about one (1) 100 watt panel. That doesn't need a MPPT. Save the $$ until you have more panels.

 

[akrvbob]

And here I always thought any charge controller fed about 14 volts to the battery and then the state of charge of the battery determined the amps flowing from the controller. 7.5 x 14. Oh sorry, the original question was about one (1) 100 watt panel. That doesn't need a MPPT. Save the $$ until you have more panels.

That's a common mistake. A PWM controller is only capable of reducing the voltage so it doesn't overcharge the battery. That's it's only job to keep too much power from going into your battery. It can NOT increase the amps going into the battery.

In the winter, when it's colder and your panels voltage is going up to it's highest point, 18 volts or more, and your batteries are at their lowest point because it's dark so much and the battery itself is cold, down to 11-12 volts that 100 watt panel will only be putting 60-70 watts into your battery.  

When you need the power the most, the PWM will give you the least.  The MPPT, on the other hand, would give you the full 100 watts. If that's not worth it to you, then that's a choice you have to make. 

You can spend another $120 for a second 100 watt panel (plus more feet to mount it and more wire to run it and more time to install it) to make up for the poor work of the PWM controller, or you can spend $60 more for the Ecoworthy MPPT controller that jimindenver recommends so highly. 

For most of us, the best choice is 200 watts feeding a MPPT controller. That will get us through the low-sun, dark days of winter and the storms of summer.

The worst thing to do with solar is to prepare for the best conditions, when 100 watts with a PWM might be okay. Instead, prepare for the worst and revel in all the extra power in the summer when things are their best.  
Bob

 

[66788]

[font=Arial, Helvetica, sans-serif]Maximum Power Point Tracking is electronic tracking - usually digital. The charge controller looks at the output of the panels, and compares it to the battery voltage. It then figures out what is the best power that the panel can put out to charge the battery. It takes this and converts it to best voltage to get maximum AMPS into the battery. (Remember, it is Amps into the battery that counts). Most modern MPPT's are around 93-97% efficient in the conversion. You typically get a 20 to 45% power gain in winter and 10-15% in summer. Actual gain can vary widely depending weather, temperature, battery state of charge, and other factors.[/font]

OK, assuming the above is correct and there is a 10-15% increase in charging power in the summer, that means that instead of completely charging my system in 3 1/2 hours,  it will charge in 3 hours and 11 minutes?   Is that really important to me?

In wintertime I can tilt my panels 55% to maximize the low angle of the winter sun.  I'll bet this makes a bigger difference than leaving them flat and using MMPT.

Either system will be effective for its intended purpose, but the PWM systems using reliable components will cost far less than the MPPT system utilizing the same quality components, while the performance difference actually achieved dictates the economic viability of the initial purchase.

As to the quality of Chinese built electronics, I'd like to say that there are varying degrees of quality.  
Highest quality is when a foreign company sources the electronic components and has them assembled in China for them.  Lowest quality come from Chinese originated products that use substandard electronic components in products of their own design.

Hence a major solar component seller has its products "assembled" in China, but using electronic components provided to the assembler from its own sources will be of higher quality and durability than just buying a cheap product on eBay, like the hundreds of so called MMPT charge controllers that one will find using the search function with the term "MMPT charge controller".

A good friend of mine who works for the FAA just took specialty classes in Oklahoma City for FAA radio maintenance and the instructors told him of the hit and miss quality of Chinese electronics, based not on manufacturing techniques, but on the individual quality of the components used in assembly.   One will find 1% tolerance resistors in quality products, and 20% tolerance resistors in cheap products.   If ALL the tolerances fall within specifications, then you are lucky and the product last a long time.   If some of the tolerances are outside spec, and this is very likely, then the product will work for a while, but eventually the out of tolerance components will cause failure to one or more parts of the device and the product will fail.

This has been my observation for the last 10 years or so as well.  For that very reason I prefer to pay the extra money for quality goods and not have to worry down the road.

Buying Chinese originated electronics is a crapshoot.   You pay your money and take your chances.

 

[66788]

Morningstar controllers are not American made.

This is true now.  They are assembled in China using electronic components sourced by MorningStar to meet their specs for their products.   Please see my other post for this discussion in more detail.

I have used a Chinese made MPPT controller for 3 years with out fail. You can pick them up for $85 with free shipping. They have developed a following and are known to do what they say they will. Side by side they milk every bit as much power out of a 250w GT panel as my Morningstar TS-MPPT-60 does.

Rely on the experts? Writing a blog does not make one a expert. Setting up and using a single system successfully doesn't either. I've been in PV for years, built and ran three systems, tested four different panels of two different types in every possible conditions on two different controllers. Done things the experts said could never happen even though they had never tried. Were I to have kept it all in a blog this conversation may have been about me and not Handy Bob.

The legal definition of an expert is one who has knowledge beyond that of a lay person.  You probably are in fact an expert by definition.

Things the experts have been wrong on

Mono vs poly. General knowledge, advertising and hype say that mono's are so much better than polys. My first mono vs poly test showed the mono noticeably smaller in foot print, put out less in bright light and was useless in overcast situations while the poly dropped according to how thick the overcast was. I was told I was wrong, my mono panel was faulty, I didn't understand, all the test show.....

The next year I picked up two 245w mono's and used them for a year. They would drop from 17a each to 2.38a as soon as the clouds rolled in. I knew my 230w poly could do 5a in pea soup so I started looking for the mono's replacements. The three 250w polys will do up to 25a in heavy overcast and that will keep us going.

Monos also put out less power when hot, so in the summertime in hot climates, they are inferior in most applications.

When I first started I noticed that once the battery was in float that I could turn on everything in the trailer and the battery wouldn't lose voltage, the system was running those things directly. I could see the amps produced rise and fall as buttons were pushed.  No no I was told by the experts. Battery runs things and the solar charges the batteries. I said but wait the battery is in float and unchanging in voltage. They said it happened so fast you can't see it on a meter or controller display. So I took a panel, controller, battery, inverter and load, got it all running and pulled put the battery. Load kept running and so ended that conversation with the experts.

My PWM system on float increases the amps in when additional loads are placed on the system, but the battery voltage remains constant.   I have not pulled the battery, as Morningstar warns against disconnecting/reconnecting the battery under load.

When I decided to take the concept farther and run a small air conditioner in the rare instance we need it, I was laughed at. Even after I set it up and tested I was told it wouldn't work. How funny it is now that I can run the little A/C from 10 am to 3 pm and still toss the batteries a bone while it runs. Before and after it does pull small amounts from the battery but when the compressor cycles, the batteries catch up.

As for the advantage of a smaller MPPT system. A Eco-worthy 20 amp MPPT, a inexpensive GT poly panel and the same wiring, etc you would need for a PWM system can come in under $500, be easier to mount and provide more power than a 12v system costing the same. A number of people copied my original system of a 230-250w GT panel with the Eco-w, I never told them they should, they just liked my results.

Then again, I'm no expert, I just design systems that do things the experts say can't be done.

 

[66788]

Lots of opinions about MPPT vs. PWM.

I'm going to order an MPPT controller to conduct my own research on my system in the Dodge van that I am familiar with.   It will be MPPT but not a cheapie, as I want fully adjustable set points as well as conformal coating over the entire circuit board.

Results to be posted upon completion of the tests.  

 

[66788]

Further developments...

Just got off the phone with Northern Arizona Solar and Wind.

In my particular case, he recommended keeping my Morningstar ProStar 30 versus switching to MPPT.

The logic was that I am running 2 different 12v panels, a Kyocera 120 watt and a Solex 85 watt. If I were to go MPPT it would charge the system, but the true MPPT would not work, whereas with the PWM it will take both panels and charge accordingly. Mixing panels is a consideration in choosing the correct charge controller.

Now for my step van that I am building, 4 Kyocera 120 watt panels, MPPT will be an advantage. I will use the TriStar 45 MPPT for that build. He recommended wiring two panels in series, then both sets in parallel. Higher voltage, smaller gauge wire, but two sets for possible shade issues.

If it ain't broke, don't fix it.

 

[akrvbob]

OK, assuming the above is correct and there is a 10-15% increase in charging power in the summer, that means that instead of completely charging my system in 3 1/2 hours,  it will charge in 3 hours and 11 minutes?   Is that really important to me?

In wintertime I can tilt my panels 55% to maximize the low angle of the winter sun.  I'll bet this makes a bigger difference than leaving them flat and using MMPT.

In your situation this is all moot because of your miss-match in panels, but I still want to make things as clear as possible.

I explained in the post above why the MPPT works better in the winter because a cool panel has higher voltage and the higher voltage is totally wasted with a PWM controller. 

Tilting your panels cannot produce more amps, all it can do is increase the volts, which it will do. But your PWM controller can't do anything with those volts and they will be flushed down the toilet because they would damage your battery. 

Without an MPPT controller, tilting your panels does little good. It does give you more power very early and late in the day, but that is a limited amount of good because the days are short--the sun comes up late and sets early so there is little time between sunrise and noon.

There is a reason that panels have such high voltage and that's because it varies so much with the seasons. 

Nominal voltage - 17 volt
Summer heat = 15 volts
Winter cold = 18 volts

Yes, in the summer the voltage of the battery and the panel is closer so it doesn't do as much good and the long days means that the battery gets power very late into the evening so you draw less from the battery storage. The panel is at 15 volts and the battery is at 14--very close to each other.

On the other hand, in the winter, when the battery is cold and being used much more it's voltage tends to be lower. The sun sets by 4:30 PM and you are drawing power the rest of the evening. The panel is at 18 volt and the battery is at 12=BIG difference. A PWM controller can't do anything with those volts, they are all wasted.

The big difference between what the panel puts out and what the battery needs means that a MPPT works EXTREMELY WELL in the winter WHEN YOU NEED IT MOST!!!! 

I'm going to say it again, PLAN YOUR SYSTEM AROUND THE WORST CONDITIONS, NOT THE BEST!!!!

Just because you don't need MPPT in the summer doesn't mean you shouldn't get it--WINTER IS COMING!
Bob

 

[jimindenver]

66788

Thank you for the compliment but I am far from anything close to an expert. I can tell you things that I have done with GT MPPT systems but that is about it. Most of it has come by reading as much as I can get my hands on.

I did do a series of test this summer on parallel vs series and the effect of miss matched panels. Easy to do with MSview, the logger and all of the charts. Aren't y'all glad I didn't bore you with it. lol

 

[66788]

Actually I'd be interested in what you found out about mismatched panels, and parallel vs. series.

 

[highdesertranger]

x2 on what 66788 just posted. btw what does 66788 stand for. higdesertranger