MorningStar Tristar or Midnight Charge Controller For Small Off Grid System?

[rs14smith]

Hi all,

I'm the type of person that enjoys being able to log data from a system such as a solar system. I've seen MorningStar's web portal that allows you to see in real time the different information about your solar system, and also logs data. I've also heard that Midnight's controllers also allow you to do similar things.

I'm at the point where I'm ready to upgrade my current PWM charge controller to a MPPT controller, and the Morningstar TriStar 45A model caught my attention just because I see that used more often, but I just wanted to make sure that's the best route to take if logging data is important to you?

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My current system:
4x 12v 100Watt Panels
Optimum Operating Current per panel (Imp): 5.29A
Short-Circuit Current per panel (Isc): 5.75A
Connection style: all panels hooked up in parallel

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Thanks

[Amy@altE]

I'm assuming it is a 12V battery system? With an MPPT charge controller, you could change the panels to be wired in series and have 1/4 the current and 4x the voltage on your wire, greatly reducing voltage drop.

Your panels have 5.75A ISC x 4 of them x 1.25 NEC = 28.75A, so at least a 30A charge controller is needed.

I'm not sure if you wanted to monitor the data remotely, only Morninstar's 60A version has internet, their 30A and 45A do not. You can connect the smaller ones to a USB port using their new USB Adapter if you have a laptop locally. http://www.morningstarcorp.com/produ...erbus-adapter/

[rs14smith]

I'm assuming it is a 12V battery system? With an MPPT charge controller, you could change the panels to be wired in series and have 1/4 the current and 4x the voltage on your wire, greatly reducing voltage drop.

Your panels have 5.75A ISC x 4 of them x 1.25 NEC = 28.75A, so at least a 30A charge controller is needed.

I'm not sure if you wanted to monitor the data remotely, only Morninstar's 60A version has internet, their 30A and 45A do not. You can connect the smaller ones to a USB port using their new USB Adapter if you have a laptop locally. http://www.morningstarcorp.com/produ...erbus-adapter/

When I viewed their website, and the specs for the 45Amp model, it appeared that it did have "data" logging capablity which I assumed meant it allows you to use an ethernet cord to see the information.

But anyway, my main question here is, what makes Morningstar's controller better than Midnight's charge controller that is around the same specs? I definitely want to expand my system in the future, but both controller manufacturers seem to allow that, so I'm a bit lost as to which one to go with.

[Sunking]

Your panels have 5.75A ISC x 4 of them x 1.25 NEC = 28.75A, so at least a 30A charge controller is needed.

Huh? If you are talking about the wiring then OK. But that is not required for the charge controller. He has 400 watts of panels. Does not matter how they are configured with MPPT. The input current can be either 5.75 amps or 23 amps, but at 12 volt battery the output is 33 amps. So what is the 1.25 Correction Factor for the Controller used for? I understand the wiring part, but not the controller as its output is Panel Wattage / Battery Voltage.

[Amy@altE]

Huh? If you are talking about the wiring then OK. But that is not required for the charge controller. He has 400 watts of panels. Does not matter how they are configured with MPPT. The input current can be either 5.75 amps or 23 amps, but at 12 volt battery the output is 33 amps. So what is the 1.25 Correction Factor for the Controller used for? I understand the wiring part, but not the controller as its output is Panel Wattage / Battery Voltage.

The charge controller output is the same for either wiring, so the amp rating required is the same, since charge controllers are rated in their output, not input. The manuals for all of the ones I am familiar with say to multiply the Isc by 1.25 for NEC. None of them actually mention a reference, so I assume it is either for 690.8(A)(1)* or for over-irradiance. I need to double check.

Therefore, if wired in parallel, Isc x 4 strings x 1.25, or if wired in series, the charge controller drops the voltage by 4 so it increases the current x4, so same math.

Regardless, if you use any of the manufacturers' string sizers, you will find that the max Isc output is always 80% of their rating.

*690.8(A)(1) Photovoltaic Source Circuit Currents. The maximum current shall be the sum of parallel module rated short-circuit currents multiplied by 125 percent.

[rs14smith]

Here you can also find that the 45Amp model does have the same communication features as the 60Amp model: http://www.morningstarcorp.com/compa...81&product_03=

I would prefer to sale my PWM Morningstar Prostar 30, and just stick with the Morningstar brand for now and upgrade to the 45Amp MPPT model. However, if Midnite's charge controller is better for data logging, then maybe it's worth making the switch?

[Sunking]

*690.8(A)(1) Photovoltaic Source Circuit Currents. The maximum current shall be the sum of parallel module rated short-circuit currents multiplied by 125 percent.

That is for the wire, not controller. For the wiring between panels in controllers on a battery system unless the run is very short do not really apply in the design because of voltage drop is taken into accout which will almost always be larger then the minimum NEC requirement. Grid Tied systems running several hundred volts are another story.

[Amy@altE]

Here you can also find that the 45Amp model does have the same communication features as the 60Amp model: http://www.morningstarcorp.com/compa...81&product_03=

I would prefer to sale my PWM Morningstar Prostar 30, and just stick with the Morningstar brand for now and upgrade to the 45Amp MPPT model. However, if Midnite's charge controller is better for data logging, then maybe it's worth making the switch?

The data port is not the same as Ethernet. Data is possible locally on all versions via optional adapters, remote Ethernet is only available on the 60A.
Here on page 51 it says Ethernet is only on the TS-MPPT-60. http://www.morningstarcorp.com/wp-co...ors-Manual.pdf

I suggest you read the manuals of both Morningstar and Midnite, and decide which logging features are most important to you. Both are great charge controllers, I think it's a personal choice which meets your needs better.

[Amy@altE]

That is for the wire, not controller. For the wiring between panels in controllers on a battery system unless the run is very short do not really apply in the design because of voltage drop is taken into accout which will almost always be larger then the minimum NEC requirement. Grid Tied systems running several hundred volts are another story.

Derek, you've got me obsessed on this today. All of the manuals refer to a NEC safety margin of 1.25 when sizing the charge controller, not just the wiring, but no one is giving a reference number. The one I gave was my guess while getting from the horses mouth. I just sent off a note asking 1 manufacturer, about to send a couple more out to see who can get me the specifics.

Example from Morningstar manual:
To comply with the National Electric Code (NEC), the current rating of the controller must be equal to or greater than 125% of the solar array’s short circuit current output (Isc). Therefore, the maximum allowable solar array input to the TriStar MPPT 150V controller for compliance with the NEC is:
TS-MPPT-30: 24 amps Isc*
TS-MPPT-45: 36 amps Isc*
TS-MPPT-60: 48 amps Isc*
*Solar array Isc @ STC

[Sunking]

Amy NEC does not cover equipment as it is out of the NEC jurisdiction. Equipment is UL. I think what you are reading from Manufactures is CYA and ignorance like putting a Ground Stud and telling you to connect it to A GROUND ROD. When you buy a gizmo the manufacture tells you what the input requirement is like not to exceed X volts @ Y amps using a minimum Z gauge conductor.

If you design based on Voltage drop like 2%, then unless you are operating at high voltages or very short distances you will always exceed NEC requirement. Most of the quality Charge Controllers will give you a Table of Wire sizes based on source voltages and distance. The smallest wire will always meet or exceed minimum NEC requirement.

I am not trying to put you down, I am trying to understand where you are coming from. I do not know of anywhere in 690 the code requires the CC to be derated. Nor do I know of any code article that requires the equipment to be derated. What I do know is the code does requires conductors to be up-sized if the equipment is continuous duty, and a solar panel source circuit is considered continuous duty. But NEC jurisdiction ends at the end of the wire going to the equipment. Only exception I can think of is Buss Capacity.

[rs14smith]

The data port is not the same as Ethernet. Data is possible locally on all versions via optional adapters, remote Ethernet is only available on the 60A.
Here on page 51 it says Ethernet is only on the TS-MPPT-60. http://www.morningstarcorp.com/wp-co...ors-Manual.pdf

I suggest you read the manuals of both Morningstar and Midnite, and decide which logging features are most important to you. Both are great charge controllers, I think it's a personal choice which meets your needs better.

You're right. Good catch. I wish they would do a better job of outlining that on their webpage.

Thanks!

[Amy@altE]

That's why I like this forum, it's making me rethink the status quo and question things I learned 7 years ago, and have been teaching forward. I do stand by oversizing the charge controller by 25%, every manufacturers' manual and string sizer tells you to. (Is it UL or NEC or both that tells you to refer to manufacturer's instructions?) I'm just trying to come up with the why. I had been taught that it was for over-irradiance, but again, I can't find the source, and the charge controllers had the 3-hour continuous already included, so just do the one 1.25.

I was about to release a new video today on sizing a charge controller, I put it on hold until I get the answer of why.

[Amy@altE]

You're right. Good catch. I wish they would do a better job of outlining that on their webpage.

Thanks!

That's a mistake you make once, and then remember for a looongggg time. I agree, they do not make it clear at all.

[Sunking]

I do stand by oversizing the charge controller by 25%, every manufacturers' manual and string sizer tells you to.

No problem with that Amy from a code POV, but it does allow your competitor to underbid you, and makes the manufacture mo money. So you need to understand the difference between minimum code requirements and biz requirements. One effects the other.

(Is it UL or NEC or both that tells you to refer to manufacturer's instructions?)

Technically both but NEC is the one that gets you in trouble with the AHJ and courts. Good example is compression connectors. NEC basically says follow all manufactures directions for making a certified listed connector (UL). The manufacture will tell you what specific tool is required. You cannot use the truck to run over and squeeze on a compression connector. Redneck Tools and Southern Engineering is not allowed.

Here is me in my Red Neck Swimming Pool



Here is what happens to Red Necks doing Electrical Wiring.

[Sunking]

it's making me rethink the status quo and question things I learned 7 years ago, and have been teaching forward.

Mistake everyone makes. We trust educators to give us the correct information without question. Unfortunately there is a reason why some teachers teach. Takes a while and some age to question everything. I am not saying what you were taught was wrong. Over sizing is not wrong, but it is not required and is a design issue and not a requirement.

In any event do not take the manufactures word for any code issue. They might be Covering their butts with over kill and it is important you understand when you see that. It could cost you a job. If they cite a code, go read it. If you do not understand go to Mike Holt Forum and either I or one of the other mods or members will get you the right info.