Advice wanted:MPPT charge controller

[Wabbit]

Need to buy better CC. Want MPPT for future expansion. Want to be able to control\fine tune charging\floating charge values.

Currently 100W solar. Want MPPT controller at around 40A.(future panels). Want to be able to add battery monitor later. Want to pay under $200....if there should be another want here, add it pls. The budget is not set hard at 200, but it would be nice. I really don't see more than 400 watts being put into it, so 30A CC would also work(I think). Main thing I want is to be able to fine tune the voltage on charging\floating. The whole put more juice into them than the "presets" let you. If that makes sense. Ideas?

 

[jonsun]

Personally since money is an option I would take a PWM Morningstar over a mid-grade MPPT for anything under 1kw on an rv.

doing the real world calculations MPPT is really just a gimmick on small systems with decent panels that don't have ridiculous over-voltage.

 

[jonsun]

a 100w 17v panels will have about 1v drop at controller. It's max current becomes 6.25A.

this isthe first place where they get you...a 12v system doesnt charge at 12v, it charges at 14.4v
the second is MPPT only charges during bulk phase.

so you're PWM system is outputing about 90w.

in reality you pull say 65% charge out daily. It's only going to see about an extra 10w until the bank hits 85% (or wherever the absorption phase is set to kick in usually 80-85%).

Then assuming we do not use a generator to bulk charge, which would be silly on a mobile setup which alone makes MPPT worthless, those 10w on say a 100Ah bank gives us about .69A per hour or 20 minutes faster charge to reach absorption phase. and reaching that point should take about 1/3 of the sunlight day so your system charges the battery to 100% either way.

if you quadruple the system and the amp draw it stays the same. about 15-20 minutes faster bulk charge....on a system that will easily charge 100% either way.

the nature of solar is you cant build it on the margins to the point where 20 minutes means something.

 

[Wabbit]

I have heard a lot about the Bogart SC-2030 PWM controller along with the TM-2030 monitor. That runs about $300 for both. Can I do better with that $300 than that? If not, case closed lol.

 

[flying kurbmaster]

I have a Blue Sky mppt 3000. I am pretty sure it will do everything you are asking for and should come in around your budget.

 

[Wabbit]

The bluesky has a max set voltage point of 15.5. Is that high enough for good people like Handy Bob? Others seem to go to 17 volts max. Am I misunderstanding the numbers?

So between the SC-2030 CC & TM-2030 meter or the bluesky MPPT 3000w\temp sensor(approx same price), which way do I go...

End game is 400w solar & approx 400ah battery pack. I want my battery pack to last as long as possible.

 

[frater secessus]

the second is MPPT only charges during bulk phase.

Assuming zero load on the system.  If there is load on the system during acceptance/float the MPPT function can provide more power, up to Vmp, as needed.  The PWM system is stuck on the power output at Vabs/Vfloat.

IMO the major problem with MPPT controllers with small panels (other than $$$) is the extra power the controller itself uses.  PWM Controllers tend to use much less power to do their work.  It is conceivable that a 40a MPPT controller on a 100w panel might self-consume enough power to offset any MPPT gains.  The Morningstar Tristars are pretty thirsty;  I think the 45a model self-consumes 4w or similar.

 

[jonsun]

Oh OK. Makes sense.

But still barely more than half an amp not counting controller consumption or voltage loss from heat.

You could come out making less with them. (Plus the whole generator thing)

 

[frater secessus]

Need to buy better CC. Want MPPT for future expansion. Want to be able to control\fine tune charging\floating charge values.
...
Want MPPT controller at around 40A.(future panels). Want to be able to add battery monitor later. Want to pay under $200....

This might generate some controversy, but here goes:  the Tracer line of Chinese MPPT has a decent reputation, has configurable setpoints, PC and meter configurable, self-consumes about 1w, and fits your budget.

30a 3215BN  ~$180
40a 4215BN  ~$200
New MT-50 meter for either is about $35 although can be less if bundled.

The previous-generation controllers are about $40 less.  With one of those and the new meter you would be <= $200. 

Note:  Renogy resells these under their own name but bodges the firmware so it doesn't work with the generic meter linked above.  You guessed it:  their bodged meter costs $20 more.

 

[Sabatical]

We have had great results using midnite solar kid controllers in several different setups. I don't understand all the math and figures that were outlined above and i don't post this as a nose thumb to anybody. Just sharing great performance in numerous settings. Disclaimer here is that we have to use mppt due to having higher voltage panels.
With the "whiz bang jr." accessory which allows end amp setting and real time monitoring, we were all in for a touch more than your budget. This should be a one time purchase though. My thought was buy the very best i could afford one time rather than the cheapest thing that would do the job several times.
I was told by a good buddy who knows more than i that pwm would be fine with 12v panels as long as i could max out it's capacity. Otherwise mppt would give me an approx 30% gain. I have found that we have never needed more than we had even when i continue to shrink the system from it's original size. We currently run 260 watts and 225 amp hours in an always boondocked travel trailer.
As with all things, YMMV. Best of luck.

Sent from my SCH-I435 using Tapatalk

 

[jimindenver]

It's hard to explain the advantages of MPPT sometimes even to those that sell the stuff. Suffice to say at times it will net you much more than the basic numbers most claim. tthe benefit mid day when your battery is up an the panel is at full power, minimal. The benefit early on when your battery is low is much more as you get the full power of the panel no matter what the voltage of the battery is.

That said, while I can understand wanting to be able to upgrade in the future, if you are not ready right now you may want to hold off. A extra panel will provide more power now and you never know what will sell at what price tomorrow. In one years time the price to enter MPPT at the level I needed dropped from over $300 to under $100 with the release of the first affordable functioning MPPT controller. Since then a number of affordable units have been released and the number grows yearly as more companies get into the market. Also some of the controllers sold by the likes of Renogy are just older versions of Tracer MPPT controllers. They function but are not as nice as Tracers newer offerings.

Panels are changing too. You can now get a 435w panel for a fraction of what four 100w panels sell for. You may not want to continue down the same road by the time you are ready to upgrade.

 

[jonsun]

I was told by a good buddy who knows more than i that pwm would be fine with 12v panels as long as i could max out it's capacity. 

That's something I've never heard before. MPPT and PWM are exactly the same when the battery is above 80%. They only do that boost during bulk charging. Cause absorption charge is literally tapering the amps, then float charge bring the volts down to 13.4 or so.

Like we were saying earlier if you're panels are lower volt (i.e. good quality 16.5-17), cable run fairly long, and the panels really hot, the MMPT cause it consumes power itself, and because of voltage drop in the wire run and panel, actually causes a net loss.

you really have to do the math and research cause the marketing is confusing. It makes it out like 20% more power, you'd be a fool not to buy this!!!!

here's a good discussion
http://www.cruisersforum.com/forums/f14/mppt-vs-pwm-solar-regulators-88728.html

 

[blars]

MPPT is preferred for LiFePO4, not only will the lower charge voltage take more advantage than Lead, they can be damaged by even tiny pulses of 4v per cell or more, which may occur on PWM near full charge.

 

[jonsun]

haha if only they weren't the price of a new RV!

 

[jonsun]

It's hard to explain the advantages of MPPT sometimes even to those that sell the stuff. Suffice to say at times it will net you much more than the basic numbers most claim. 

I agree. by hooking panels up in series or by using 30v+ panels, which can be cheaper, you will see even bigger gains than claimed. 

Its a good idea to run significantly higher voltage panels if you're doing very long cable runs, Like say from an open field to a house or camper.

But again if you're using ~17v panels on a van roof, especially sub 200w, it's really not a good investment and can easily be harmful.

 

[Sabatical]

I have been admiring the bogart engineering charging system for a while now. I have myself convinced that if i ever get rid of the higher voltage panels and kid cc setup, i would put together a system using the tri metric parts. In my mind it is far easier to add or subtract 12v panels as needs change than to do the same with higher wattage panels. However if i were to be spending a lot of time in a northern climate where fall and winter sun is low and charging hours are precious, i might not make the switch if my sytem was sized closely to my needs. We have lived using battery power in the northeast with a small scale system. Even with mppt we spent many days not reaching 100 percent charge. Granted there were trees involved and the orientation was not optimal but it was the best we could do under the circumstances.

That being said, we are currently near two people who have similar 12v with pwm setups. One uses a samlex controller and the other uses the bogart controller. Both systems utilize the tri metric battery monitor. Side by side comparison shows that the bogart system reaches float about an hour earlier, give or take, as reported by the owner of the samlex system. They would not ever switch to mppt but would definately switch to the bogart charging system.

With so many choices out there, coming to a decision can be daunting. Starting from scratch, i would consider that living conditions, desires, climate, and financial means are ever changing. I would lean towards a system that was easily adaptable even if it was not the perfect one all the time.


Sent from my SCH-I435 using Tapatalk

 

[Trebor English]

Aside from high voltage panels the point of mppt is to take the 17 volt 5 amp power and charge the depleted battery with 5.5 amps at 13 volts.  Like an inverter Watts will be lost but unlike resistance alone Amps will be gained.  The problem is that the gain only happens when the charge voltage is low and input voltage is high.  When the sun is high enough to get some good mppt Amp gain some bulk charging has happened and the required voltage is 14+ and the benefit evaporates.

 

[jonsun]

^Yep and if it's a small system it actually starts outputting less than cause it eats juice itself

 

[MikeRuth]

Morning Star TS-45 PWM for me on 2 120 Watt panels has been rock solid. Fully adjustable via laptop and or several options via dip switches.
Rated at 45 Amps. Get the remote temp sensor as well and your still under $200.00

Morning Star is an awesome company and support is as good as it gets.
Just saying this works for me.

 

[Trebor English]

Original post was about wanting control. I bought a low price cheap $20 Mohoo PWM controller. The instructions are the result of several translations and not clear. Control is limited.

The way the unit works is that when the sun comes up the switch is turned on and charging is limited by the battery and circuit resistance. When the unit senses a voltage level in excess of a programmed level it rapidly turns the switch on and off to maintain the voltage at the programmed level. The sun goes down and charging stops. The load control goes by voltage and time.

The instructions contain the words absorption equalize and float. I call those two actual charging modes current limited and voltage limited. Some people call them bulk and absorption. Renogy calls them bulk and boost. I set THE charge voltage level (called float by Mohoo) to 14.4 for my group size 24 flooded 12 volt 70 Ah "deep cycle" battery. When the weather gets hot in the summer I'll change the voltage to 14.1. If I were in a cold place I'd have it at 14.7.

There is no green light that comes on to announce that the mode is called "float" and charging is now stopped.

It seems to me that its not frugal to spend a lot more to accommodate stuff I might buy and having settings for things that might not make much difference. The $20 controller I bought seems to be available on line now for $10 to $12.