TriStar MPPT and other questions?

[nodine]

First off let me say that I am a newbie to solar. Just finished installing my system, a TriStar MPPT 45 and three 160 watt panels from AM Solar.

1. Has anyone installed these panels securing them only by the 3M tape that comes on the AM Solar mounting brackets? We have a smooth fiberglass roof and cleaned each contact area with OPPS before applying the brackets. They seem secure even when I pull up on the panels. Can't help but worry a little if they will hold up over time. Looking for feed back from anyone who has secured the panels using only the 3M tape. I can always added the screws but hate to drill unnecessary holes in the roof.

2. The TriStar MPPT charge controller always seems to stay in MPPT mode and does not raise the battery voltage high enough to charge the batteries. I have seen the display as high as 200 watts but all the power seems to be going to the motorhome load and the voltage on the battery stays well below 13 volts. I just looked and the voltage was 12.4 volts. Yesterday I let the coach get down to 65 % SOC (we have the Magnum BMK) and the voltage from the TriStar never went high enough to charge the batteries. The solar panels are reading 17 volts. Do I need to connect them in series to increase the voltage to the TriStar so the batteries will charge?

Thanks,

Bob

[Reed Cundiff]

If AM Solar thinks the tape is sufficient, it probably is; however, our panels are bolted down with S-flanges. We know that the flanges work. Unnecessarily drilling holes in the roof is a bother, but not as much as having the panels fly off. We have hit some big bumps in Yucatan (friends behind said our 5th wheel went 2' off the ground) and they stayed on.

We also have a TriStar MPPT-45 controller on our system.

Maximum power point tracking (MPPT) is a technique that grid connected inverters, solar battery chargers and similar devices use to get the maximum possible power from solar panels (taken directly from Wikipedia). This is a great read

So I would guess that the batteries are charging but never get to the voltage for absorb.

If you want real battery experts for answers on MPPT and batteries, go to Solar Panel Talk. Some of them can get into heated discussions but the answers are correct.

Putting the panels in series to get higher voltage to controller would decrease power loss from the panels but this would probably require re-programming the controller. These can be programmed to do a lot of things. Ours takes 90 V from the panels in series and sets it to charge the LFP battery bank at 48 V nominal. If you have a 40' motor-home, you might need more panels. You certainly have the space for them. Solar is like Crackerjacks "the more you have, the more you want!"
Reed and Elaine

[Bumps]

Regarding your first question, I think I would use screws and double-sided tape, if that was an option. Those panels get a lot of wind and vibration up there! Better safe than sorry!

Regarding your second question, I don't know enough to offer more than just general comments. Here is where I might start:

1. I'd check the connection between the TriStar and the battery bank -- wire size and solid connections are extremely important.

2. At that connection to the battery bank, are the POS and NEG from the TriStar connected to the same battery (assuming you have 12volt batteries) or are the POS and NEG connected to batteries at opposite ends of the battery bank -- you want to be sure all of the batteries are getting equal benefit from the TriStar, not just the first battery in the group, so connecting at opposite ends is desireable.

3. It's a bit counter-intuitive, but solar panels will provide more power if they are cooler, than if they are hotter. Ergo, if your PV is flat-mounted on the roof they will run hotter and produce less current. Mounting them 1" above the roof will allow them to run cooler and produce more power to the TriStar.

Thinking out loud,

\ken

[mgscott4]

Check your programming on your morningstar. What voltage did you tell to go to absorbtion mode? 13.5 volts

[Bumps]

Here is a better picture of the air gap between the roof and the PV. \ken

[pasdad1]

How many and what type of batteries? What gauge wire is run from panels to controller? What gauge wire is run from controller to batteries?

Are you sure there is NO shadow on any of the solar panels? Even the slightest shadow will decrease output from that panel enormously! Are all panels wired in parallel ?

Are you making your readings with all coach systems "off" ? Might help to diagnose, if you disconnect the positive wire from the batteries to the coach...... That way there is no load on the batteries, and all power going in can be accounted for.

[MutinyGuy]

I had my solar panels installed by AMSolar 4.5 yrs ago...they were fine after all that time...if you applied the tape as instructed you should have no problems.

[Uncle Dave]

Pretty sure one of the bennies of that controller is that you can wire in series and take advantage of the multiplied volts and subsequent MPPT convert to amps.

Uncle Dave

[twinboat]

Wired in parallel, 480 watts @ 17 volts = 28.5 amps. You need about 6 or 8 gauge wire to run 15 feet with a 3% loss.

From the controller to the battery at 480 watts @13.5 volts = 35 amps. again you need about 6 gauge wire.

If you wire the panels in series, you change the system volts to 51 volts. Now you figure 160 watts @ 51 volts = 11 amps. Now you can use 12 or 14 gauge wire for your 15 foot run to the controller but still need 6 gauge out to your batteries.

The above numbers are not exact, but it gives you an idea of how to wire solar panels.

Remember the distance between panels and controller is" there and back", not one way.

The TriStar 45 can handle up to 150 volts from the panels with out any setting changes.

I have a TriStar 60 and 3-225 watt 35 volt grid tie panels, run in series with 14 gauge wire, to the controller 6 feet away on my Trawler. The output is only 3 feet to the batteries and I needed to run 6 gauge wire.
My Motorhome has 3 100 watt 17 volt panels, in series and I am running 12 gauge wire, 16 feet to the Mppt controller and 8 gauge, 3 feet to the batteries.

Both systems work great. I get my 14.2 volts after a few hours of good sun.
I spend 6 months living aboard and seldom run the generator. This summer, I have been living in the Motorhome 2 months with the solar and have only run the generator 4 or 5 times, during the cloudy days.

[nodine]

Originally Posted by MutinyGuy

I had my solar panels installed by AMSolar 4.5 yrs ago...they were fine after all that time...if you applied the tape as instructed you should have no problems.

Thanks MutinyGuy, I feel better to hear someone has been running the mounts for 4.5 years without issues. I did call AM Solar yesterday and they advised that if properly installed the 3M tape will hold the panels. They did suggest that coat the area where the L portion of the brackets meet the roof with Dicor. This is to keep chemicals used to clean the roof from attacking the 3M tape.

Bob

[nodine]

Originally Posted by twinboat

Wired in parallel, 480 watts @ 17 volts = 28.5 amps. You need about 6 or 8 gauge wire to run 15 feet with a 3% loss.

From the controller to the battery at 480 watts @13.5 volts = 35 amps. again you need about 6 gauge wire.

If you wire the panels in series, you change the system volts to 51 volts. Now you figure 160 watts @ 51 volts = 11 amps. Now you can use 12 or 14 gauge wire for your 15 foot run to the controller but still need 6 gauge out to your batteries.

The above numbers are not exact, but it gives you an idea of how to wire solar panels.

Remember the distance between panels and controller is" there and back", not one way.

The TriStar 45 can handle up to 150 volts from the panels with out any setting changes.

I have a TriStar 60 and 3-225 watt 35 volt grid tie panels, run in series with 14 gauge wire, to the controller 6 feet away on my Trawler. The output is only 3 feet to the batteries and I needed to run 6 gauge wire.
My Motorhome has 3 100 watt 17 volt panels, in series and I am running 12 gauge wire, 16 feet to the Mppt controller and 8 gauge, 3 feet to the batteries.

Both systems work great. I get my 14.2 volts after a few hours of good sun.
I spend 6 months living aboard and seldom run the generator. This summer, I have been living in the Motorhome 2 months with the solar and have only run the generator 4 or 5 times, during the cloudy days.

My system is basically a kit from AM Solar and has 10 ga wire from the panels to the combiner box and about 8 feet of 4 ga wire from the combiner box to the TriStar 45 MPPT charger. About 5 feet of 4 ga wire from the charger to the battery bank. I talked to AM Solar yesterday and they feel I am better off keeping the panels in parallel. I still don't have an answer to my question as to why the TriStar stays in MPPT mode all the time and does not increase the charge voltage to a point that the batteries will be charged. AM Solar suggested that I do not have enough wattage in my panels and will need to run the generator each morning to bring the batteries back up. I am adding one more panel which will bring my total to 640 watts.

Bob

[BendOR]

Originally Posted by nodine

My system is basically a kit from AM Solar and has 10 ga wire from the panels to the combiner box and about 8 feet of 4 ga wire from the combiner box to the TriStar 45 MPPT charger. About 5 feet of 4 ga wire from the charger to the battery bank. I talked to AM Solar yesterday and they feel I am better off keeping the panels in parallel. I still don't have an answer to my question as to why the TriStar stays in MPPT mode all the time and does not increase the charge voltage to a point that the batteries will be charged. AM Solar suggested that I do not have enough wattage in my panels and will need to run the generator each morning to bring the batteries back up. I am adding one more panel which will bring my total to 640 watts.
Bob

First of all, you have PWM (17-18v) panels feeding an MPPT controller. This works well when pairs of PWM panels are hooked up in series then paralleled to the combo box then to an MPPT controller. With 3 panels, all parallel, there is no high voltage advantage for the MPPT controller to work with. Add that 4th panel.

An MPPT controller only does its MPPT’ing while in bulk charge, after that, its all PWM for absorb and float.

Suggestions: While you have good sun on all panels-

Check the voltage input to the batts with a voltmeter.

Check the voltage output of the controller. Review its settings. Factory settings may be too low for you.

Check the voltage output from the combo box.

Check and review all solar system connections.

Call Morningstar and ask what the Tri-Star does with an 18v input.

Remember, you want to conserve volts after the controller, a 2% loss is too great. Better is 1% or less. May want to increase wire size from controller to batts.

[nodine]

Originally Posted by BendOR

First of all, you have PWM (17-18v) panels feeding an MPPT controller. This works well when pairs of PWM panels are hooked up in series then paralleled to the combo box then to an MPPT controller. With 3 panels, all parallel, there is no high voltage advantage for the MPPT controller to work with. Add that 4th panel.

An MPPT controller only does its MPPT’ing while in bulk charge, after that, its all PWM for absorb and float.

Suggestions: While you have good sun on all panels-

Check the voltage input to the batts with a voltmeter.

Check the voltage output of the controller. Review its settings. Factory settings may be too low for you.

Check the voltage output from the combo box.

Check and review all solar system connections.

Call Morningstar and ask what the Tri-Star does with an 18v input.

Remember, you want to conserve volts after the controller, a 2% loss is too great. Better is 1% or less. May want to increase wire size from controller to batts.

BENDOR,

I have the 4th panel on the way.

Are you saying I would be better off to connect two panels in series x 2 and then connect the two pairs in parallel so basically my Vmpp voltage is 37 volts and my Impp is 17.3 amps? This is what I was thinking but when AM Solar said I would be better off to keep all the panels in parallel I dropped the thought. Sounds like to get the benefit of the MPPT charger I need to get the voltage up above the 17 to 18 volts the panels are now putting out. That was my thinking because we assumed there is some voltage drop across the regulator and for the TriStar to up the battery voltage to 14 volts a higher input voltage than 17 would be required. We also assumed if the panels were series/parallel the TriStar MPPT would commence charging earlier in the day and continue later in the evening. Is that an accurate assumption?

Thanks for your reply and I can tell you know something about the subject.

Bob

[pasdad1]

The higher voltage due to wiring in series is great.........until a shadow falls on part of the panel. The shadow will knock down power not only on the panel it falls on, but also the other panel connected in series with that one.

Be careful even of shadows from air conditioners, roof vents, satellite dishes, etc. if you can work out good placement of the panels avoiding this issue as much as possible, it will work well. Bad placement could make the array produce less power than having all in parallel.