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

[K1ngN0thing]

My $160 Tristar TS-45 PWM is apparently faulty, and due to my procrastination, I've missed the return window. I'm now looking to replace it with an affordable MPPT that's just "good enough." Wondering what you all are using, what to avoid, etc.

 

[K1ngN0thing]

Should also mention I have an AGM battery.

 

[akrvbob]

Have you called them yet, there is a fair chance a tech can walk you through fixing it and if not I'm almost certain it has a 5 year warranty so you should be able to send it back.

Here is a Tracer (who makes Renogys controller) 10 amp MPPT for $70. Doesn't get much cheaper than that!
http://amzn.to/1U1eLMd

Bob

 

[K1ngN0thing]

Ordered from a third party seller, so I'm waiting for them to get back to me about a potential return. Don't think I'll bother trying to fix it. Don't want to risk it breaking again later on. $70 isn't too bad.

 

[K1ngN0thing]

Ordered the Tracer.

 

[66788]

There is a lot of authority on various forums and from manufacturers that a 12v system of less than 400 watts does not benefit from MPPT.

I've used PWM for years without problems on my small systems and they perform fine.   Morningstar is my preferred brand, but there are others that are well made as well.

Currently I'm using a 200 watt system (Kyocera panels, Morningstar PRO30 PWM controller, AGM Gp 31 battery, and it's the best system I've had to date.    It runs the CPAP, ceiling exhaust fan, interior fan, ARB compressor fridge, lights, and charges the iPhone and Samsung tablet at night.    All that usually consumes 30-40 percent of my battery reserves, but I'm fully charged within hours after the sun comes up.

I credit the efficiency of the system to good components and short/direct wiring from the panels to the charge controller, and from the charge controller to the battery using much heavier than recommended stranded wire (chart calls for #10, I use #4 and #6)    This will allow me to expand the system if need be without changing the controller or wiring.

 

[jimindenver]

The Eco worthy 20a MPPT controller is the least expensive functioning MPPT controller out there. They can be picked up for $85 in including shipping off of ebay. $102 with shipping directly off of the site. I do agree that with a single 100w panel that you wont see much gain from it.

There are any number of small PWM controllers on ebay. The solar 30 is rebadged into many names and sold for various prices. I am pretty sure you can find the same unit under the Eco-worthy, windy nation, renogy and tracer sites. I think the cheapest for it is $30 or so.

I wanted to speak to the concept of cheap. Cheap mean it cost less because they cut corners in the build. You really want the same quality for less call inexpensive. There is a big difference. Also you need to understand what features you need. Buy a controller that wont allow you the proper voltage to charge that AGM and it may kill an expensive battery in short order.

 

[blars]

There is a lot of authority on various forums and from manufacturers that a 12v system of less than 400 watts does not benefit from MPPT.

No, what the ones that know what they are talking about say is it is not cost efficient, but they are generally not taking into account roof real estate, weight, more complexity in tilting, etc. As panel prices and MPPT controler prices vary, the break even for MPPT will change as well. For many RVers with less than 400 watts of panels MPPT makes sense.

 

[MikeRuth]

King with your receipt from the retailer, third party as you call them you can contact MorningStar, Your receipt is all you need. And the TS-45 is a dawg gone good unit.

My 2 cents,.

Take care.

 

[K1ngN0thing]

Tristar's been returned, mppt installed. Seeing as I only have 100 watts (will eventually upgrade to 300, but that's going to be many years from now) I figured I'd go with MPPT to get the most out of my one panel.

 

[ccbreder]

yep. what 66788 posted.

 

[jimindenver]

That's a bummer about the Morningstar controller. I really like the control mine gives me to charge the Lifelines. No auto program will meet their needs, I have to create it. Other batteries are happier with more normal voltages and programs.

The difference between a straight up PWM controller and a MPPT controller is how much of the panels power can be used at any given time, and how that power is controlled before you reach absorb and float voltages. Both use PWM to charge your battery. (shocking huh)

A PWM controller links the battery to the panel. The batterys voltage limits the panel until you reach absorb and float voltages, at that point the acceptance rate controls how many amps goes in. You set the voltage set points and the battery does the rest. It is simple but the downside is by linking the battery to the panel, any excess power is wasted in all modes.

A MPPT controller doesn't link the panel to the battery, so any power produced is available at any time, in any mode. It does this via a buck converter that takes the DC power form the panel, converts it to AC and then back to DC again. The MPPT part is a chip that tells the controller how to use the power to bring the battery up to absorb voltage where the battery can take control again. They make a big deal out of it but it is the buck converter that is the real star of the show.

Another advantage is since a MPPT controller can use higher voltages, you can run your 100w panels in series. When one panel would be useless putting out 11 volts in low light, two in series will put out 22v and the controller will convert it to usable power for charging. This could be early in the morning before the sun is high enough or mid day when it is cloudy. The advantage is ignored by many but it's better than nothing.

 

[ZoNiE]

I have 400W and a Midnight Kid MPPT on my TT. Not cheap, but US made and the support is excellent. I have even met the designer at the Intersolar show in SFO last July. He responds to users on their forum as well. I expect long life and if not, endless support.

I'm running 3X Kyocera 130 GT's in parallel. When I add the fourth, I will rewire the setup for two series parallel strings to take advantage of the higher voltage.

I originally was going to use the three Soyndra 173's, I got for nearly nothing, which are ~90V so I needed the MPPT. They were just too big.

I may use them for my hot tub pump or sell them... Not sure.

MPPT is the way to go for higher wattage, but yeah, under 200 watts PWM is fine.

 

[ccbreder]

I stole this from Handy Bob's. One of the better sites for solar power information. Thank Handy Bob!
CHARGE CONTROLLERS:
All full timers should use either what I have (Tristar PWM) or spring for the Tristar MPPT. I personally only recommend MPPT if the system is approaching 600 watts, if the solar panels are those high voltage 44 cell units so that MPPT is needed to use the excess voltage, or if the existing wiring is too small and series wiring the panels can be done to improve voltage drop. I will not do this unless the panels wired in series are identical and will absolutely never have shadowing issues. I will never series more than two panels on RV’s. Doing so with the whole roof is asking for shadow problems because a shadow that shuts one panel off will also shut off all panels wired in series with that one. I also would prefer rewiring with larger cables if less expensive than the extra $$ that the MPPT costs. I do not believe that MPPT, even Morningstar’s (which I believe to be superior to the others) nets enough extra energy over time to justify the cost. I know it works during perfect conditions, but just how much of the time does that happen? People that talk about 25 & 30% boost are just like those that report their fuel mileage when looking at a one time measurement reported by their truck’s computer. Spend the money on another solar panel and get more energy all of the time, even when cloudy. I set controllers in motor homes slightly conservatively (14.6V) due to the chassis battery interconnection and over voltage alarm problems. I don’t like it, but there doesn’t seem to be much choice.

 

[akrvbob]

I stole this from Handy Bob's. One of the better sites for solar power information. Thank Handy Bob!
CHARGE CONTROLLERS:
All full timers should use either what I have (Tristar PWM) or spring for the Tristar MPPT.  This is a ridiculous statement! There are many other great controllers to consider. This alone would make me question everything he says 

I personally only recommend MPPT if the system is approaching 600 watts, if the solar panels are those high voltage 44 cell units so that MPPT is needed to use the excess voltage, or if the existing wiring is too small and series wiring the panels can be done to improve voltage drop. I will not do this unless the panels wired in series are identical and will absolutely never have shadowing issues. I will never series more than two panels on RV’s. Doing so with the whole roof is asking for shadow problems because a shadow that shuts one panel off will also shut off all panels wired in series with that one. I also would prefer rewiring with larger cables if less expensive than the extra $$ that the MPPT costs. I do not believe that MPPT, even Morningstar’s (which I believe to be superior to the others) nets enough extra energy over time to justify the cost. I know it works during perfect conditions, but just how much of the time does that happen? People that talk about 25 & 30% boost are just like those that report their fuel mileage when looking at a one time measurement reported by their truck’s computer. Spend the money on another solar panel and get more energy all of the time, even when cloudy. I set controllers in motor homes slightly conservatively (14.6V) due to the chassis battery interconnection and over voltage alarm problems. I don’t like it, but there doesn’t seem to be much choice.

I think he's wrong. 

It's a simple fact that nearly all our solar panels put out about 18 volts of power (or more, and the more they make the more a PWM controller wastes up to it's limits) and the battery can rarely take more than 14 volts. The 4 volt difference is simply lost with a PWM, flushed down the toilet.

A PWMs only job is to read the battery and reduce the voltage coming into it so it doesn't damage the battery. It's dumb, that's all it does is waste power your panels are creating.

An MPPT controller is smart, that's what you are paying for. It reads the battery and steps down the voltage and increases the amps. That's something a PWM CANNOT do. It can NOT increase amps. For that, you buy a MPPT controller, so the most amps are going into the battery as possible. 

If you want 200 watts of power going into your batteries, with a MPPT controller you only need to buy 200 watts of panels. With a PWM controller you have to buy 300 to make up for the 4 volts being flushed down the toilet. That's at least another $120 for a panel, then mounting and then wiring and then extra space on the roof and extra risk from shadows and hailstorms and extra weight and extra cleaning.

The big difference in prices between MPPT and PWM is people are comparing apples and oranges. Usually they are comparing stripped down cheap Chinese models to high end, feature rich, American models. When you compare apples to apples, the price difference is not that great.

I prefer to buy quality, American made MPPT controllers. But, it's just my opinion and we all know about those.
Bob

 

[jimindenver]

Who is to say someone is right or wrong as long as their needs are met? Designing solar is a combination of many things when you get right down to it. Roof space, needs, panels and batteries all impact the controller decision. King plans on expending so it is best to buy for that rather than buy again down the road.

As for size vs MPPT/PWM again to each their own but I know two 100 or 150w panels in series on a MPPT controller will have a noticeable difference over all. Now would the difference be more than a third panel on PWM, probably not but you have to have room for that extra panel. Each situation is different.

Last thing to consider is when Handy Bob wrote that, things were different. The least expensive MPPT controllers did make the small advantages in smaller systems impractical for the cost. Now you can run a 300w system on a $85 MPPT controller.

 

[66788]

I think he's wrong. 

It's a simple fact that nearly all our solar panels put out about 18 volts of power (or more, and the more they make the more a PWM controller wastes up to it's limits) and the battery can rarely take more than 14 volts. The 4 volt difference is simply lost with a PWM, flushed down the toilet.

A PWMs only job is to read the battery and reduce the voltage coming into it so it doesn't damage the battery. It's dumb, that's all it does is waste power your panels are creating.

An MPPT controller is smart, that's what you are paying for. It reads the battery and steps down the voltage and increases the amps. That's something a PWM CANNOT do. It can NOT increase amps. For that, you buy a MPPT controller, so the most amps are going into the battery as possible. 

If you want 200 watts of power going into your batteries, with a MPPT controller you only need to buy 200 watts of panels. With a PWM controller you have to buy 300 to make up for the 4 volts being flushed down the toilet. That's at least another $120 for a panel, then mounting and then wiring and then extra space on the roof and extra risk from shadows and hailstorms and extra weight and extra cleaning.

The big difference in prices between MPPT and PWM is people are comparing apples and oranges. Usually they are comparing stripped down cheap Chinese models to high end, feature rich, American models. When you compare apples to apples, the price difference is not that great.

I prefer to buy quality, American made MPPT controllers. But, it's just my opinion and we all know about those.
Bob

Sorry AKRVBob, I think you are wrong.   Handy Bob has the experience and background to be the expert on this issue, and his advice is in line with most other experts on the small (400 watt and under) 12v RV systems.

I have personally created 12v systems that were marginal at best in performance, but after reading his treatise I designed my current system using his suggestions and I can say it is the best performing system I have ever had.

A deep cycle battery will only accept the amperage that it needs, so throwing more amperage at it when it doesn't need it is also not beneficial.   I have 2 Xantrex 3-stage battery chargers, one 10 amps and one 20 amps.  There are times when I connect the 20 amp unit and it charges at the same rate as the 10 amp unit.   Even though it CAN charge at a full 20 amps, the battery doesn't always accept amperage in excess of 6-9 amps, so using the 20 amp charger is not better than using the 10 amp charger.

My GP31 AGM charges up in a few short hours with 200 watts of solar, so what benefit would there be for me to use MPPT on this small 12v system? 

None.

 

[ZoNiE]

Yeah, I think Handy Bob needs to broaden his horizons. Sure, Experience speaks, but a morningstar and trimetric are not the only good solution. Midnight has an MPPT that is perfect for RV's with all the features of both built in. A few other controllers out there are just as good. His info is a bit dated...

 

[jimindenver]

66788

The best you can do is express what works for you and why, if it applies to someones situation great , It doesn't mean they think you are wrong if they chose a different route. There are a lot of opinions, options and situations out there.

Read Handy Bob, Jack Mayer, the 12v side of life and more. Each RV and solar forum has it's own experts, sometimes with drastically different opinions. Once you have a general feeling you find the real gold mine is the experiences of the different users with different needs and situations. After awhile you get a idea of what does what and can really tailor a system to fit your own.

 

[66788]

66788

The best you can do is express what works for you and why, if it applies to someones situation great , It doesn't mean they think you are wrong if they chose a different route. There are a lot of opinions, options and situations out there.

Read Handy Bob, Jack Mayer, the 12v side of life and more. Each RV and solar forum has it's own experts, sometimes with drastically different opinions. Once you have a general feeling you find the real gold mine is the experiences  of the different users with different needs and situations. After awhile you get a idea of what does what and can really tailor a system to fit your own.

In this case that does not apply.  We are talking pure science here, not opinions or voodoo.  The question is "Is there a benefit to MMPT in under 400 watt 12v RV solar systems?"

Either there is, or there isn't.

I've had experiences with my systems, just as Bob has had experiences with his.  Like all laymen, I rely on the advice of experts in finding the solution.   I find the other experts more compelling than our Bob on this one issue.

Bob's advice on American made controllers is spot on, as the quality of the electronics goes to the heart of the reliability of the entire system.   For that very reason, I use Kyocera panels, MorningStar controllers, and good AGM batteries.  I know very well from first hand experience with Chinese electronics that they are not for me.   They work initially, but in the long march (pun intended) the failure rate is very high.

A search of MMPT Charge Controllers on eBay will yield hundreds of different Chinese charge controllers from $15.00 and up.   Do you really think you can get a quality MMPT charge controller for under a hundred bucks?  Not hardly, but there they are, waiting for the suckers to buy them.   Some of them are not real MMPT controllers, but they are marketed as such and the victims who buy them don't know the difference.

I would rather have a good American PWM charge controller than any Chinese MMPT controller.   That's how I do things, and quality always trumps price to me.

I think the major objection to most charge controllers, be they PWM or MMPT. is that they don't have adequately adjustable set points.   Each battery charges best to its own individual specs.   Being able to adjust the set points to the correct voltages is of paramount importance.

The MorningStar TS controls do that in both PWM and MPPT.   That is why they were recommended.  There is no substitute for a system made from known good components.