Airstream--Upgrade to MPPT Charge Controller?

System
System Posts: 2,511 admin
in Solar Product Reviews & Opinions #1
I currently have an RV with two Kyrocera 130s wired in parallel and the Morningstar Sun Saver Duo feeding 4 six volt Lifeline AGMs. I am considering switching to the Morningstar MPPT mentioned here and wiring the panels in series to gain some additional output from the panels. My wire size from the panels to the controller is approx 20 feet and run in 10 ga. stranded. Does this sound like a viable improvement on charge efficiency?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Charge Controller Q's - MorningStar Sunsaver MPPT

    You can use a voltage drop calculator to work out the numbers:
    • 10 awg wire
    • 2*130 watts * 1/17.6 v = 14.8 amps into battery
    • 20' circuit length (40' wire run--read calculator setup for which to use)
    • Voltage drop = 0.7 volt drop (perfectly reasonable)
    • Power = V*I = 14.5 volts batt * 14.8 amps = 215 watts into battery
    Now, same panels assuming in series, using a MPPT charge controller with 5% loss:
    • 2*130 watts * 1/(2*17.6 volts) = 7.4 amps Imp
    • Voltage drop = 0.4 volt drop (better)
    • 2*130 watts * 0.95= 247 watts into battery
    • 2*130 watts * 0.95 * 1/14.5 volts batt = 17 amps into battery
    There is a bit of an advantage to a MPPT controller--but it is not going to improve your power collection that much (a 15 amp MPPT MorningStar charge controller is ~$235).

    Overall, given inefficiencies and if this is in warm weather--a 15 amp controller is not the worst solution. Larger controllers cost more...

    A 30 amp Rogue MPPT controller is $295

    A 45 amp MPPT MorningStar is $412.

    And you can get another 50 watt solar panel for $251... If your current PWM controller can handle more current and you have room for another panel--not the worst solution either.

    What direction do you think you would like to take?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: Airstream--Upgrade to MPPT Charge Controller?

    Airstream,

    I moved your question to its own thread--usually makes it easier for us to keep track of your specific installation and your questions.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #4
    Re: Airstream--Upgrade to MPPT Charge Controller?

    Thank you Bill for your reply,

    My existing PWM controller does have the capacity to add up to another 130watt panel, however I don't have enough room to even add a 50 watt panel.

    I read the manual on the Rogue 30A controller you attached and really like what that controller has to offer for only a few bucks more.

    So - I'm going to go with the Rogue 30A.

    Paul
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  • bryanl
    bryanl Solar Expert Posts: 175 ✭✭✭✭✭
    #5
    Re: Airstream--Upgrade to MPPT Charge Controller?

    The problem with RV installations is that very few can be large enough to get to the kilowatt nominal levels. That means that optimizations have very little real impact on total function. (i.e. the cost effectiveness of optimizing the system have rapidly diminishing returns)

    At these energy levels, the variance in use patterns can easily overwhelm even significant changes in energy systems. This is why adding batteries to the RV won't usually provide the satisfaction many seek.

    Once you make the lifestyle adjustments to accommodate the limited RV resources, the next effort that really pays off is towards preserving capital and that means taking care of your battery bank. That is not easy.

    Full timing boondockers who have adjusted to living off their limited solar capability often have their batteries in a perpetual state of discharge. Even if minor, this can significantly reduce battery life.

    Occasional or weekend RVers fall into the problem of occasional deep discharge and poor maintenance charging that doesn't assure a top charge without overcharging and doesn't inhibit sulfation and stratification of electrolyte.

    Once you have a decent system, I'd suggest putting your efforts in how to make sure you can get a full and complete charge on your batteries at least weekly and how you can inhibit sulfation buildup when they are idle.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #6
    Re: Airstream--Upgrade to MPPT Charge Controller?

    Another possibility is to get one or two "portable" panels that you can setup outside the trailer... Can be very handy if you park under shade / don't have a choice where you park for best sun. Use a heavy duty (10 awg or whatever extension cord) to connect your panels. I would use a non-standard plug on the panels (not 120 VAC) to prevent "accidents".

    Obviously, you will have to protect against wind and theft too... A small Honda eu2000i or eu1000i (or equivalent) can also be a fuel efficient backup option when used for backup charging (many RV generators are 6kW or larger and consume large amounts of fuel for the little power needed to keep your bank charged--same as with trying to use the tow vehicle to recharge the battery bank too (lots of fuel, small amount of electrical power).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • audredger
    audredger Solar Expert Posts: 272 ✭✭
    #7
    Re: Airstream--Upgrade to MPPT Charge Controller?

    A word of caution: I bought a used Airstream that had solar added to it.. they had brought the panel feed in through the refrigerator vent (OK) but then hooked the controller output to the + side of the refrigerator! The dealer fried two refrigerator control board before he figured out the problem. The wire from the refrigerator to fuse block is too small and all that current blew the control board.

    My Airstream has a trough that runs front to back on the street side and had plenty of room for cable to the battery.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #8
    Re: Airstream--Upgrade to MPPT Charge Controller?

    "Another possibility is to get one or two "portable" panels that you can setup outside the trailer... Can be very handy if you park under shade / don't have a choice where you park for best sun. Use a heavy duty (10 awg or whatever extension cord) to connect your panels. I would use a non-standard plug on the panels (not 120 VAC) to prevent "accidents"."

    I do the same thing. I have a couple of panels that "float" with the season, some times on the roof, sometimes in front, sometimes out on the ice. I made up a Anderson connector system so that I can plug mine in any number of configurations. Using the Anderson's keeps from plugging stuff in backwards.

    http://store.solar-electric.com/anhicupoco.html

    Tony
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  • System2
    System2 Posts: 6,290 admin
    #9
    Re: Airstream--Upgrade to MPPT Charge Controller?

    Thanks all for the replies. As far as the trailer goes, Airstream provides, on later models, what they call solar prewire. It is a 10ga yellow and 10ga green wire run from the dc bus into the fridge compartment. Yellow is power (sun) and green is the ground. That said, I didn't trust that they ran the wire in the shortest run so I pulled new 10ga wire down the fridge stack and though the trough on the street side.

    We monitor the power usage religously. I use the TriMetric 2020 for that and I am careful not to draw the batteries down to 80% without getting them back up to a full charge either by use of the panels or a Honda 3000 genset (which I prefer not to use if possible) When in storage the panels maintain the charge on the batteries.

    90% of the time I have no problem with the balance of battery capacity and ability to recharge from the panels. Winter use is more challenging with the lower sun. I have the ablility to tilt one panel at a time to improve efficiency and I became interested in the MPPT controllers when I learned of their better use of the panels voltage output.

    I think the idea of a free panel or two that I can carry in the truck is a super idea. I've got some extra MC4 connectors that I could use for that purpose.
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  • brulaz
    brulaz Solar Expert Posts: 31 ✭✭
    #10
    Re: Airstream--Upgrade to MPPT Charge Controller?
    airstreamer wrote: »
    I currently have an RV with two Kyrocera 130s wired in parallel and the Morningstar Sun Saver Duo feeding 4 six volt Lifeline AGMs. I am considering switching to the Morningstar MPPT mentioned here and wiring the panels in series to gain some additional output from the panels. My wire size from the panels to the controller is approx 20 feet and run in 10 ga. stranded. Does this sound like a viable improvement on charge efficiency?

    Airstreamer, we are considering something similar for our Trailer: two Kyocera 130W in series with the Rogue MPPT controller.

    But our panels would travel in the back of our pick-up and be setup at sunny spot at each campsite. Do the Kyocera 130W panels seem rugged enough for this amount of handling and vibration? The newer LPU ones have a bit thicker frame (1.8" vs 1.4").


    (Sorry to hijack your thread ...)
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  • thenderson4
    thenderson4 Registered Users Posts: 16 ✭✭
    #11
    Re: Airstream--Upgrade to MPPT Charge Controller?

    brulaz and airstreamer,

    I also am planning to put solar power on/in a travel trailer. My first phase is finished. I have changed out all the 12 volt DC lighting to LED. That pretty much removed all my load except for the inverter needed for any 120 volt AC needs.
    The controller I want to use is a Morningstar Sunsaver MPPT 15L (15 amp) 200 watt max @ 12 volt or 400 watt max @ 24 volt. I will be using the 12 volt mode. (already own this controller)

    The two batteries are Deka High Energy Series 24HR3000 in parellel.

    I want somebody to recommend a solar panel. I want the panel to be as close to the 200 watt max as possible. I plan to use the panel loose, not attached to RV. I have a small panel and can see the benefits of placing the panel in the sun and keeping the RV in the shade. PS: can be one panel or two.

    Thanks, readers.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #12
    Re: Airstream--Upgrade to MPPT Charge Controller?

    You can put upwards of 260 watts of so of solar panels on the MorningStar MPPT 15 amp controller without "wasting" much in the way of dollars.

    Usually, it is only in very cold weather and reflection from snow fields when you get anywhere near maximum power from the array for more than a few minutes.

    And the controller itself will work just fine with more than 200 watts of panels (no damage, no overheating--the controller may not use 100% of the available power if you have more PV Watts than the controller can output to the battery bank).

    200+ watt panels are, physically, pretty large. You might want to look at a pair of smaller panels (100-130 watt) for ones that are a bit easier to manage (panel weight and wind loading).

    Also, make sure your panels are staked/bolted down well... They are just thin window glass (tempered) and an errant gust can take them out in nothing flat. A shattered panel is not repairable and will quickly loose its output current/voltage from the damage/moisture/etc..

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • thenderson4
    thenderson4 Registered Users Posts: 16 ✭✭
    #13
    Re: Airstream--Upgrade to MPPT Charge Controller?

    Thank you, I had thought that two panels around 130 - 135 watts in parallel would work. I have the meter bus & cable to monitor all rates.

    My SUV roof rack is also an option for the mounting of panels. I many areas, daytime is spent hiking or on bikes so the SUV could provide a solid location for panels.

    UPS is also a better way to ship I had read if the package is small enough.

    Which two would you buy for your own use with a controller like this?

    Thanks.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #14
    Re: Airstream--Upgrade to MPPT Charge Controller?

    The Kyocea 135 Watt units would be a good choice.

    I don't work at/for NAWS--so you would have to call them and see what else they have around in the 100-135 watt range. They may have some odds and ends around for a good price.

    I guess you are in Alabama or so--You might find local suppliers (after shipping) may be easier (shipping glass panels requires a lot of good packing--costs money to ship).

    NAWS has a list of panels they sell--all brands they have had good experience with. Your best pricing is usually in the >100 watt panel sizes.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • brulaz
    brulaz Solar Expert Posts: 31 ✭✭
    #15
    Re: Airstream--Upgrade to MPPT Charge Controller?

    Thanks BB, I guess we will go with the 2 Kyocera 135s wired in series and the Rogue controller.

    The Kyoceras are a good size and weight, easy to handle. We can get a lightweight portable stand for them and stake that into the ground. And I'll build a box with soft foam inside for the pickup bed.

    Time to get away from the crowded campsites ...
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #16
    Re: Airstream--Upgrade to MPPT Charge Controller?

    Brulaz,

    Should be a nice combination.... By the way, keep the charge controller near the battery with good sized wire (see manual). It is critical that the controller have very little voltage drop to the battery bank (with low voltage drop) for proper battery charging. Having the long cables between the solar panels and the charge controllers is fine--you may have a bit more power/voltage drop--but it does not affect charging.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • brulaz
    brulaz Solar Expert Posts: 31 ✭✭
    #17
    Re: Airstream--Upgrade to MPPT Charge Controller?
    BB. wrote: »
    By the way, keep the charge controller near the battery with good sized wire (see manual). It is critical that the controller have very little voltage drop to the battery bank (with low voltage drop) for proper battery charging.

    Oh. Thanks, I wasn't aware of that. The trailer has a large battery compartment so that's where I'll put the Rogue controller. And it can take 6 ga stranded, I think, so maybe I'll use that to the Battery. Well actually to the breaker in the breaker box, which brings up another question.

    I've been looking at the diagram in the Rogue manual (Fig 8.2.2, p29). There would a Solar Panel breaker (15A for the Kyoceras) between the two serial panels and the controller. Then another breaker between the controller (20-30A ?) and the +12V power bar. And a third breaker between the battery and the +12V power bar. (He also has a DC Load Breaker and an Inverter breaker coming off the +12V power bar).

    All this makes sense to me, from both a safety and able-to-isolate-components perspective, but is there a concern about voltage drops across all these? I guess they should be designed not to cause any problems.

    - Bruce
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #18
    Re: Airstream--Upgrade to MPPT Charge Controller?

    You do not need any breaker between the controller and the solar panels (that I am aware of).

    And, yes, you should have the others. Cost of safety.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • brulaz
    brulaz Solar Expert Posts: 31 ✭✭
    #19
    Re: Airstream--Upgrade to MPPT Charge Controller?
    BB. wrote: »
    You do not need any breaker between the controller and the solar panels (that I am aware of).

    Hmmm. The Kyocera 135W spec sheet lists a Max Fuse spec of 15A. I just assumed that was the fuse/breaker that the Rogue diagram has between the panels and the controller.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #20
    Re: Airstream--Upgrade to MPPT Charge Controller?

    You only need the series fuse if you have three or more panels in parallel (or three or more series strings in parallel).

    The series fuse in the solar array string is to prevent a short circuit from being fed by other paralleled strings... One or two parallel strings do not need the fuse.

    From page 30 of the manual:
    8.4 Disconnects and overcurrent protection

    Pursuant to National Electric Code requirements (and others which may have jurisdiction in your locale), disconnects are required for both the input and output of the MPT-3024. It is recommended that the PV disconnect should be rated for 30 amps to comply with NEC requirements. The recommended disconnect between the MPT-3024 and the battery should be rated for 40 amps. All disconnects should be rated for DC (direct current) use.

    I don't quite agree with this statement by the NEC... I think it is "overkill". You are welcome to do it... But two 135 watt solar panels in series will only ever output 10 amps maximum... No way to ever trip a 30 amp breaker... Plus the Rogue MPPT controller will limit its input current based on design.

    Of course, I am not the building inspector and placing a 30 amp breaker/fuse in the PV line is not going to hurt anything either.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • brulaz
    brulaz Solar Expert Posts: 31 ✭✭
    #21
    Re: Airstream--Upgrade to MPPT Charge Controller?
    BB. wrote: »
    You only need the series fuse if you have three or more panels in parallel (or three or more series strings in parallel).
    ...
    Of course, I am not the building inspector and placing a 30 amp breaker/fuse in the PV line is not going to hurt anything either.

    Thanks for the clarification, Bill. As this is a Travel Trailer installation, I don't have to worry about any inspections, but that also means I'd better get it right on my own. Hence all the questions. This board is a great resource.

    So I'll pass on the SP to Controller breaker. I don't need it for component isolation either as the panels will come in on MC4 connectors. It may also save me from having to put in another breaker box.
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  • lorelec
    lorelec Solar Expert Posts: 200 ✭✭
    #22
    Re: Airstream--Upgrade to MPPT Charge Controller?

    Some of the NEC doesn't make much sense. 690-9 contains an exception (b) that might allow you to get away (code-wise) without using overcurrent protection on the input of the controller. However, this is usually interpreted to apply to systems that don't include batteries. The concern is that the batteries could backfeed through the controller if there was ever a fault -- although the overcurrent protection on the output of the controller would open if the fault was on the controller side and sourcing current from the batteries. A disconnect (as opposed to overcurrent protection) is a good idea -- it will make your life much simpler if you ever want to disconnect the PV from the controller (which may happen often as you reorganize and upgrade your system). Also, the design of the controller is such that, once it's powered up, it will continue to operate from the PV input even if you disconnect the battery (until it goes to sleep and disconnects the PV input internally). So in order to completely shut down the controller when it's powered up and out of sleep, you have to disconnect both PV and battery inputs.

    Marc
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  • brulaz
    brulaz Solar Expert Posts: 31 ✭✭
    #23
    Re: Airstream--Upgrade to MPPT Charge Controller?
    lorelec wrote: »
    So in order to completely shut down the controller when it's powered up and out of sleep, you have to disconnect both PV and battery inputs.

    Hmmm. The Rogue controller does have a small maintenance current even when it sleeps. So for my Travel Trailer installation I'll have the breaker between the controller and +12 power (which connects to the battery via another breaker) and MC4 plugs from the controller to the Solar Panels.

    When we tear down, I'll first cut the Controller/power bar breaker then disconnect the MC4's and put away the SPs. And reverse that when we set up.

    I'm really looking forward to setting this all up and giving it a try.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #24
    Re: Airstream--Upgrade to MPPT Charge Controller?

    I am not sure I would use the MC4 connectors for your traveling connectors (I am not sure how rugged they are for multiple cycles--if they have high contact pressure--they may tend to wear quickly)... Use a non-standard plug/receptacle (220, high current 120, etc.)...

    I have mixed feelings about twist locks... No matter how careful every one is--there is eventually an "event" where the vehicle drives away--A simple push fit connector works well in those cases (instead of dragging the panels behind the trailer).

    Anderson Connectors are nice too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • lorelec
    lorelec Solar Expert Posts: 200 ✭✭
    #25
    Re: Airstream--Upgrade to MPPT Charge Controller?
    Hmmm. The Rogue controller does have a small maintenance current even when it sleeps.

    The controller draws a small amount of current from the battery to power the microcontroller, signal conditioning circuitry, and display while it sleeps -- about 15mA or so at 12v (~200mW). This is normal and shouldn't be a problem unless you go for quite some time without sunlight.

    Marc
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #26
    Re: Airstream--Upgrade to MPPT Charge Controller?

    By the way guys,

    Marc/Lorelec is the designer/manufacturer/seller of the Rogue controller--so ask your questions!

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • brulaz
    brulaz Solar Expert Posts: 31 ✭✭
    #27
    Re: Airstream--Upgrade to MPPT Charge Controller?
    lorelec wrote: »
    The controller draws a small amount of current from the battery to power the microcontroller, signal conditioning circuitry, and display while it sleeps -- about 15mA or so at 12v (~200mW). This is normal and shouldn't be a problem unless you go for quite some time without sunlight.

    And in most Travel Trailer installations, when the panels are not plugged in, you are either on 110V AC charging your batteries, or connected to your Tow Vehicle which is charging your batteries. So, not a problem (although there are cases where the tow vehicle can't keep up with the trailer's current draw).

    Marc, in your manual for the Rogue, you state that the breaker between the Rogue and the battery should be 40A. But your circuit diagram has two breakers between the battery and the Rogue, separated by the +12V power bar. The 40A refers to the breaker between the +12V power bar and the Rogue, correct?

    Bill, your caution is overwhelming. If I ever drive off without disconnecting my solar panels, I will deserve the consequences. But you are probably right about the MC4 connectors. I'll find a high-current push connector.
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  • lorelec
    lorelec Solar Expert Posts: 200 ✭✭
    #28
    Re: Airstream--Upgrade to MPPT Charge Controller?
    brulaz wrote: »
    Marc, in your manual for the Rogue, you state that the breaker between the Rogue and the battery should be 40A. But your circuit diagram has two breakers between the battery and the Rogue, separated by the +12V power bar. The 40A refers to the breaker between the +12V power bar and the Rogue, correct?

    That's correct. The other breaker (from the batteries to the positive bus bar) will be rated to handle whatever load current you expect from your batteries.

    Marc
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #29
    Re: Airstream--Upgrade to MPPT Charge Controller?

    My favorite story of the twist lock connector is from a family friend as a small kid...

    Local fire department guys kept knocking out the Engine's charger/engine block heater plug while working around the station--Fixed that with a twist lock plug--You can imagine what happened next....

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • soleil
    soleil Solar Expert Posts: 45 ✭
    #30
    Re: Airstream--Upgrade to MPPT Charge Controller?

    brulaz, have you hooked up your system yet? I'm interested to hear how things are going, as I'm strongly considering the same setup for my 5th wheel.
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  • brulaz
    brulaz Solar Expert Posts: 31 ✭✭
    #31
    Re: Airstream--Upgrade to MPPT Charge Controller?
    soleil wrote: »
    brulaz, have you hooked up your system yet? I'm interested to hear how things are going, as I'm strongly considering the same setup for my 5th wheel.

    Not yet. The solar panels/controller are the last things on my todo list. I've just expanded the battery bank to 232Ah and converted many of the lights to LED. Next I want to go on a test run, measure the phantom and other loads, and just see how long we can last (down to 50-80% capacity) without charging the batteries. Maybe there are other areas where we can reduce our electricity consumption as well.

    Once we get a handle on our electrical loads, I can verify the solar panel size (we were planning on two Kyocera 135W).
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