Quick MPPT question

[BradKW]

I'm going to order stuff today or tomorrow and I'm unsure whether to get the Morningstar Tristar 45amp or the Tristar 60 amp. I have 975 watts @ 24 volts in PV.

thanks!

 

[jimindenver]

What will you bank be? At 24v the 60 will be good, not sure about 12v unless you really want to overpanel. The 45a would be over paneled at either voltage.

I like my TS-MPPT-60 but when I had it overpaneled at 12v with 970w it went into overheat protection and was only using 660w out of the 800w being produced all while getting so hot you would not want to hold on to it. My thought is over paneling is great early on and on cloudy days but with full sun, it's just not good for the controller.

 

[BradKW]

I plan to have bank at 12v basically because that's what everything I read is, and I don't really understand overpanelling

 

[blars]

With 450 watts of panels, I rarely see more than 25 amps output. Unless you are going with a 24v battery bank, you will need the 60A controller. The 60A tri-star mppt also has an ethernet port that you can get a status web page from.

 

[29chico]

I'm going to order stuff today or tomorrow and I'm unsure whether to get the Morningstar Tristar 45amp or the Tristar 60 amp. I have 975 watts @ 24 volts in PV.

thanks!

The Tristar MPPT 60 has a built in dedicated web server and Ethernet connection that should be accessible with just about any web browser.  By paying a bit more you can avoid the serial rs-232 connection in the 45 amp version.  By all means, if you you like Tourette's moments dealing with a misbehaving connection go for the 45 amp version.  Possibly MS has got the serial port issue dialed.  It is just that my most frustrating computer problems have always been with serial connections.

I paid $500 for my Tristar MPPT 60 from Arizona Wind & Sun.  Great folks.

 

[BradKW]

Thanks blars. Jim, please explain the overheating problem as it might apply to me? Do I to look even bigger than 60amp? Ty

 

[29chico]

What will you bank be? At 24v the 60 will be good, not sure about 12v unless you really want to overpanel. The 45a would be over paneled at either voltage.

I like my TS-MPPT-60 but when I had it overpaneled at 12v with 970w it went into overheat protection and was only using 660w out of the 800w being produced all while getting so hot you would not want to hold on to it. My thought is over paneling is great early on and on cloudy days but with full sun, it's just not good for the controller.

Were the 970w of panels pointed at the sun or flat mount?

I will be  flat mounting my 3 315w LG panels on my converted cargo trailer soon.  Since I am flat mounting the array I over paneled it a bit.   My plan is to have forced air cooling on the controller that is switched on at 105 degrees F by a thermostat.

 

[amwbox]

Were the 970w of panels pointed at the sun or flat mount?

I will be  flat mounting my 3 315w LG panels on my converted cargo trailer soon.  Since I am flat mounting the array I over paneled it a bit.   My plan is to have forced air cooling on the controller that is switched on at 105 degrees F by a thermostat.

Let us know how that goes. I've been investigating using a liquid cooling loop that was originally designed for PC CPU's. I could keep the radiator out of sight pretty easy that way.

 

[jimindenver]

Brad

You will likely never really see more than the TS-MPPT-60's rated limit of 800w out of your panels unless you visit me in the nose bleed section. 800w is 60a and will push the controller to it's limits during peak times. That's flat, tracking they could do 70a or so.

So in this case overpaneling will get you more amps early and max amps at peak. At peak the controller puts out some considerable heat. How much, well I could use it to run a electric heater on one end of the trailer and it on the other and cut the furnace run time down on a cool day. Running it in series so that it is converting 100+ volts down to 12v creates even more heat. Combine the over paneling for max amps and the series conversion together for a controller clipping output to save itself.

My Eco-worthy did the same when the sun hit its case, The amps dropped as the case heated up only to climb once the controller was shaded again. Had it gotten any hotter it would have shut off.

Both of my controllers overheated out in the open where they could not of had more ventilation. It would have been quicker in a small compartment so I intend on having a powered vent for the compartment, not just the controller. The same is true for the battery bay with the AGM's in it. The need to vent AGMs for gasses may be less but heat isn't good for them either. I hate fans but dislike replacing expensive gear even more.

What to do for the heat, start by wiring the panels in parallel for a lower conversion. That will take heavier wire from the roof but it will be worth it in better efficiency and less heat. I'm using 1/0 welding cable. I'm using the same for the run to the batteries, inverter, interconnects. Resistance is heat.

 

[BradKW]

Let us know how that goes. I've been investigating using a liquid cooling loop that was originally designed for PC CPU's. I could keep the radiator out of sight pretty easy that way.

That's an interesting idea...I've used closed loop cooling in my PCs for a long time. The problem I would foresee with that is they are really only made to cool a very small spot the size of a CPU, and its hard to imagine charge controllers complying with the form factor.

I used to play around with custom loops and I think that's where you'd find a solution, because you could create your own copper block to fit the device. There's lots of information about how to do that, and it's not "hard"...it's almost more work evaluating all the various designs and inter-block turbulence theories than actually making one. But then you get right back to what finally turned me off to custom loops, which is running water through a DIY setup on top of very expensive electronics...

 

[BradKW]

Brad

You will likely never really see more than the TS-MPPT-60's rated limit of 800w out of your panels unless you visit me in the nose bleed section. 800w is 60a and will push the controller to it's limits during peak times. That's flat, tracking they could do 70a or so.

So in this case overpaneling will get you more amps early and max amps at peak. At peak the controller puts out some considerable heat. How much, well I could use it to run a electric heater on one end of the trailer and it on the other and cut the furnace run time down on a cool day. Running it in series so that it is converting 100+ volts down to 12v creates even more heat. 

What to do for the heat, start by wiring the panels in parallel for a lower conversion. That will take heavier wire from the roof but it will be worth it in better efficiency and less heat. I'm using 1/0 welding cable. I'm using the same for the run to the batteries, inverter, interconnects. Resistance is heat.

I guess part of what I'm not understanding is why even 800 watts would take that unit close to capacity? Copy/paste from Morningstar stats: "[size=small][font=Arial, Helvetica, sans-serif]The TriStar TS-MPPT-60 MPPT is designed for off-grid PV systems as large as 3.0 kWp"

I read that to mean it can handle up to 3000 watts...so what am I not seeing?

Do you start your 1/0 cable at the combiner box? My panels have little connector clips that I'll need to cut off, then was thinking I'd run 10aug to the box, 1/0 to the controller...?  

ty

 

[jimindenver]

The TS-MPPT-60 is rated for 800 watts at 12v. It can take more at higher voltages.


I will have a combiner box in mu fridge vent. The 3 set of 10 gauge coming from the panels will go to bus bars and then 1/0 down to the controller. I'll have to use pin lugs for the connections to the controller and inverter.

 

[akrvbob]

In nearly everything in life buying "just barely enough" is nearly always a mistake in the long run. That's especially true with electronics where there is heat and "just barely enough" is going to mean LOTS of heat.

Spend the money and buy the right size and you'll cry once. Save the money, buy the wrong size, and cry a lot more in the long run.
Bob

 

[jimindenver]

Bob, I couldn't agree more. Even running 750 watts flatt out all day produces a lot of heat. Luckily in this case the bigger controllers are not that much more than a TS-MPPT-60.

 

[BradKW]

Looking at the Outback Flex80 ... http://www.solar-electric.com/oufl8...Z5fsr5Tv_oUIaH4Wk50H3EcZIINRFYSV4wBoC2ifw_wcB

Jim, I'm curious why you say I would have more panel output at altitude where you are, versus the rather brutal summer sun down here nearer the equator? Does the humid air filter out...hmm, just realized I don't even know what part of sunlight makes PVs work

 

[jimindenver]

Brad, there are few places that hit the light indexes we do or have the extremely thin air and low humidity. Add in a cold day and the output will make you giggly if it doesn't fry your system. Even in Denver I can not test the Isc of a panel rated for less than 10a with a 10a multi meter. The 230w can be tested on a hot day here but not at altitude.

I am old school with the buffer thing. So was most anyone else until Morningstar said otherwise a while back. A 250w panel is good for 18.5a on the 20a Eco-w, that leaves some room for freezing weather, high altitude and cloud effect. The rated limit of 275w would have it clipping without the cold, altitude and cloud effect and it doesn't like getting hot. The original rating was for 300w and they were getting a lot of complaints from over heating controllers even though they clip at 20.1a.

Of course since Morningstar has said it is okay you may not find many to agree with Bob and me. I suggest calling Morningstar and asking if the warranty will replace a unit that has been over paneled and stops functioning.

 

[rvpopeye]

Here's a crazy/cool idea !

Put 1 or 2 of those panels on a switch and turn them off when the sun is strong and turn them on when the sun is weak. You might even be able to use a thermostat next to the controller to do the switching ????????????????????

 

[BradKW]

Thank you! What I thought was a quick question has resulted in a much better understanding of how things work. So glad I'm not rushing, and have this forum as a resource.

 

[akrvbob]

At high altitude two things happen that combine to maximize a solar panels output:

1) it's colder--solar panels work best when they're cooler.
2) the air's thinner so it's blocking the sun less.

I had a friend go over a 11,000 foot pass in Colorado on a surprisingly cool day in June. It fried his Blue Sky controller. He called them and and no one could understand it, the controller was rated for the panel, but then they asked about where he had been driving, and he told them about the mountain pass.

They said that was it, that it's easy for a panel to over-volt under those conditions. It wasn't Blue Skies fault, but they over-nighted him a new controller any way--no charge!!

I'm a BIG fan of Blue Sky!! It's also an intangible reason why buying quality American made controllers can pay off in the long run.
Bob

 

[SternWake]

Another thumbs up for Blue Sky from me.


I've been using a SB2512i and the IPN pro remote battery monitor  continuously since October-2007 with a kyocera 130GT. in 2011 I added a unisolar pvl-68, but am still well below the 25 amp limit.

Only problem is I wish I spent 35$ more for the sb2512ix model which has a remote battery temperature sensor and some other functions available

A better charge controller properly programmed can greatly extend battery life, and possibly by a huge degree, making up for the extra cost of the controller in one set of batteries