What size MPPT solar controller

charlyhorscharlyhors Registered Users Posts: 3
I'm in the final stages of a solar install - last part is the panels and controller. Although we generally only use 100 AH a day, or even less, I am wanting to build for 200 AH a day eventual capacity in case we decide to replace propane refrigerator with electric (if current 10 yr old frig breaks). Our present setup is a 4 battery bank with 370AH capacity (2 banks of 2 6V 186AH Exides in series, and if we add frig would be going to 6 6V 110AH Trojans, wired in series and parallel, for a 660 AH capacity. Looking at Morningstar Tristar controllers which come in 30, 45, and 60 amp ratings. Your thoughts on which one to buy?

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: What size MPPT solar controller

    Four batteries. 370 Amp hours 6 Volt each? Configured as 370 Amp hours @ 24 Volts? Or something else?

    Reconfigure to 660 Amp hours at what Voltage? Two parallel strings of 330 Amp hours @ 24 Volts? Or three parallel strings of 220 Amp hours @ 24 Volts? Offhand I can't think of any Trojans that meet either of those specs.

    Anyway, don't go for the Trojans.
    And don't guess at capacity/usage.

    I'd recommend avoiding the Morningstar MPPT as they aren't a very good deal really. Also, at 60 Amps top one would be stressed for a 660 Amp hour battery bank. I'd suggest you get an Outback FM80 instead, or perhaps even a MidNite Classic 150 (although you may not need all its features).

    As the battery capacity goes up, so must the array. This can be a problem if too much time elapses between when you buy the first panels and when you go to increase the size; sometimes you can't find new PV to match the old, which leads to configuration difficulties and/or loss of power potential.

    At 660 Amps hours 24 Volts you'd need at least 2057 Watts of PV.

    BTW if that bank is going to be three parallel strings of 220 Amp hour GC2's I'd suggest rethinking that plan because the more parallel battery strings you have the greater the potential for uneven current amongst the batteries (which shortens lifespan).
  • charlyhorscharlyhors Registered Users Posts: 3
    Re: What size MPPT solar controller

    I've edited my question with more details on batteries. Thanks. I'm not guessing on AH usage. I currently use about 80-100 AH a day in boondocking mode, and then recharge in a park. Expecting about 100AH on adding a frig per numerous articles. I Was going to write a separate question on adding solar panels, which you have brought up. With an MPPT controller, and panels wired parallel (in this case, 2 230 W, 7.7 Amp, 29 V PV's), would I have to have similar Vmp and Imp panels when adding, or how flexible can I be with panel additions? Would appreciate your responding to the corrected question, if you would be so kind.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: What size MPPT solar controller

    Okay, 12 Volt RV system? That makes the parallel battery issues even worse. I'd recommend avoiding more than two parallel strings at that Voltage.

    Fortunately there are several different batteries available which would allow you to increase capacity without lots of parallel wiring, providing they will fit in the available space. For example there ar L16 size batteries which start at about 320 Amp hours @ 6 Volt. Two batteries, one string, about the same power capacity as three parallel strings of 110 Amp hour 6 Volts. Less wiring, fewer cells to check.


    For parallel wiring of PV's the Vmp needs to be close but the Imp can be different. For series connections it's the other way around.

    With more than two panels in parallel you should really have a fuse or breaker on each. This means using a combiner box of some sort.

    Right now you have two 230 Watt panels in parallel. 460 Watts on an MPPT controller and 12 Volt system would be about 30 Amps peak current which would be fine for any battery configuration <300 Amp hours. It would just make it for 320 Amp hours since you probably have gen/shore power to make up for the slight under-current (think periodic corrective charging).

    Those panels with a Vmp around 29 are in the standard Grid-Tie panel Voltage range so there are plenty to choose from.
  • mike95490mike95490 Solar Expert Posts: 8,377 ✭✭✭✭✭
    Re: What size MPPT solar controller
    I'd recommend avoiding the Morningstar MPPT as they aren't a very good deal

    Sadly, I am preparing to order a new controller for my in-law hut, and it's going to be a silent Tristar MPPT 60, with the meter panel. It's pricey, but I've found in my area, with my winter fuzzy cloudy conditions, that my shiny new Classic, can't match my existing tristarMPPT60. Full summer sun it's great, but in the cloudy conditions here, I don't care about the screaming cooling fans, I just want it to charge, which the Tristar does perfectly. The Classic has some nice features and remote control apps, but another one is not scheduled for me.
    Wind-Sun prices:
    Classic150 60A $610
    Tristar MPPT 60 $499 & M 2meter front $96
    Both include BTS.
    Both work well with the web interface, but the Classic has remote control App.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • HandyBobHandyBob Banned Posts: 31
    Re: What size MPPT solar controller

    Hallelujah... Somebody else who says the truth. I have been fighting the Classic problems for over a year after believing their hype. They tried to tell me I was the only one complaining. You don't really need the Morningstar meter since it only shows one side of the issue anyway... It is NOT a battery monitor. If you must have the metering, you should realize it is only a toy to play with and is not required for proper operation. Some of us just want things that work well and don't sound like a buzz saw when doing it, or have screen glitches, or try to EQ when it is shut off......... on & on. The arc fault they talk about needing to meet new code nuisance trips and shuts the power off. My 4th Classic is supposed to be coming soon and while I hope it solves the problems, I am just about ready to spend a grand that I don't have to waste for two Morningstar's to replace it. I am that upset.

    I'd like to Know why anybody would say to avoid either Morningstar or Trojan. What is the agenda behind that statement? While I do like Crown better, I still haven't seen problems with Trojan GC's, only with the L-16's and I wonder if that is batteries or charging issues.

    Charley needs to be warned about series wiring panels on RV's and the shadow issues when parking. He also needs to rethink the fridge idea. Yes, people with Mercedes always love them, but will they after a few years? I have heard from many who have had problems with their electric fridges. You won't find them on the forums, bragging about how smart they are. When mine started going bad, I bought a better built Amish cooling unit instead of an electric fridge that would absolutely guarantee that I would need to carry a generator. Our Norcold now actually works. 12 years on the road without a generator & now building a home, so far still without one. That will no doubt change next year when we have an electric fridge going in the house.

    Charley: Read my blog. You can do everything else with a lot smaller system. We lived like that for years on only 345W tilted up and later increased it to 600W that we left flat most of the time even with a 12V freezer in a storage bin. At today's prices, I would put up about 600W with a Tristar 45 and Trimetric for monitoring. If you want to have more so you can boondock more comfortably fine, but you probably don't need it.
  • HandyBobHandyBob Banned Posts: 31
    Re: What size MPPT solar controller
    For example there ar L16 size batteries which start at about 320 Amp hours @ 6 Volt. Two batteries, one string, about the same power capacity as three parallel strings of 110 Amp hour 6 Volts. Less wiring, fewer cells to check.

    L16's need higher voltage charging to take care of them than GC's do. In RV systems they usually end up destroyed in short order by undercharging. If you are an alarmist and believe what many say about RV electronics, you will not even charge GC's correctly. Suburban told somebody to not exceed 14V, which is ridiculous, but some believe it. I would not be comfortable equalizing at 16V like L16's really need in an RV during cool conditions, but I have been running up to 15.5V for years with GC's and had no issues. I've had the same fridge control board for 14 years. What does that make me... smart or lucky?

    Bottom line: L16's really do not belong in RV's. With a lot of experience in RV's I can say that six GC's wired correctly work just fine. However, (4) Crown 260's is a lot of storage and a lot less to spend than buying 6 smaller batteries and adding the extra cables. There are also other ways to go without resorting to tall batteries that absolutely need higher voltage.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: What size MPPT solar controller

    I always say people are free to disagree with me. Although I would hope they'd actually read what I write first. Understanding it as well is probably too much to hope for.

    When I dismissed the TriStar controller it was because of two factors: the first being the OP's desire to charge a 660 Amp hour battery bank. Since Morningstar's larges controller is 60 Amps one would not be able to achieve the 10% peak rate desired to have complete recharging from solar (although this is not strictly necessary where alternate charging is available). The other is the fact that it is not a good deal price-wise as the Outback FM60 has the display built-in for a little less than the TS + display costs. The 'solution' of using the computer interface is not one everyone would want as it requires a computer. How much simpler to just look at an active display. But if greater than 60 Amps is desired then no 60 Amp controller will do the job, no matter who makes it.

    Then the OP's requirement for battery capacity is lessened to 330 Amp hours, which changes the options for charge controller. At that point a Xantrex 60 MPPT could be used: <$500 and has a display. Again a better deal than the TriStar.

    As for the derogatory remarks about the MidNite Classic, hundreds of them are in use with satisfied customers including many forum members so obviously they work. They are complicated and have features many people will not need or want. Some may never be able to understand the programming well enough to get them to work ideally on their system. That's one of the appeals of the TriStar; simple DIP switch settings which give adequate performance for many systems.

    I recommend against Trojan batteries for two reasons: the first is that they tend to be more expensive for the same amount of power as opposed to Crowns or Dekas. The second is that even the T105's have higher Absorb Voltage recommendations than the other brands, and if you have to go to higher Voltage you run into problems with achieving that in limited sun time and also with a 12 Volt system difficulties with high Voltage on some loads (especially inexpensive inverters) which can be aggravating at the least.

    Your comments about L16's not being suitable for RV's merely emphasizes your lack of battery knowledge. You assume that because it is in a mobile application they will be undercharged. This happens a lot in RV systems because frankly they are badly designed to begin with and a large number of 'solar installers' out their only succeed in making them worse through application of their stubborn ignorance. Well if you undercharge any battery in any application it will be ruined. The same goes for overcharging it.

    Now I'm sure some people will merely glance at this post and not read it because they have already decided I'm wrong just because. We have a word for that sort of person: troublemaker. They are not welcome here.
  • VicVic Solar Expert Posts: 2,970 ✭✭✭✭
    Re: What size MPPT solar controller
    mike95490 wrote: »
    Sadly, I am preparing to order a new controller for my in-law hut, and it's going to be a silent Tristar MPPT 60, with the meter panel. It's pricey, but I've found in my area, with my winter fuzzy cloudy conditions, that my shiny new Classic, can't match my existing tristarMPPT60. Full summer sun it's great, but in the cloudy conditions here, I don't care about the screaming cooling fans, I just want it to charge, which the Tristar does perfectly. The Classic has some nice features and remote control apps, but another one is not scheduled for me.
    Wind-Sun prices:
    Classic150 60A $610
    Tristar MPPT 60 $499 & M 2meter front $96
    Both include BTS.
    Both work well with the web interface, but the Classic has remote control App.

    Hi Mike,

    However, from memory, in your system, the Classic is a Classic 200, and the string Vmp is something like 140 - 150 V (or close to it). Also recall that the Classic 200's PVs are facing SE, I think. Had wondered if in cloudy weather, if a non-South facing array would be significantly behind one that faces due South (in our area of CA), as it is fairly far off-axis.

    Regardless of the imprecision of my memory, the TS MPPT-60 could not survive the string Vmps that the Classic 200 is exposed to, and just thinking about the amount of power produced by these dissimilar array configurations, seems to me that any attempt to compare the Classic 200 verses the TS MPPT could not be fair, as you cannot simply swap the two PV arrays between the Classic and the TS, without FRYING the Tristar MPPT 60.

    Yes, the Classic does have fans, they do make some noise, the TS is probably quieter, BUT, IMO, Power Electronics do not belong in habitable spaces, unless care is taken to suppress acoustic noises that many devices do make.

    Not to attack you, but, just trying to add some balance. I DO love my Classics. They are not yet perfect, but MidNite is very accommodating in accepting customer's feedback (in public on their Forum, and here), to make their products even better than they are currently. Your NiFe battery is unusual, and may add to the complexity of comparing the TS to the Classic 200.

    FWIW, Good luck, Mike with your system ... the Classic 150s did get us to Float today, in overcast conditions. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • mike95490mike95490 Solar Expert Posts: 8,377 ✭✭✭✭✭
    Re: What size MPPT solar controller
    Vic wrote: »
    Hi Mike,
    However, from memory, in your system, the Classic is a Classic 200, and the string Vmp is something like 140 - 150 V (or close to it). Also recall that the Classic 200's PVs are facing SE, I think. Had wondered if in cloudy weather, if a non-South facing array would be significantly behind one that faces due South (in our area of CA), as it is fairly far off-axis....

    a) when it's cloudy, there is no axis. If there was, the hour the sun is between the 2 arrays (10am -11am) should show good matching, but it never does. As it is, the poor axis tristar outperforms the classic, when the classic has good alignment (in hazy or clouds but not in full sun).
    b) the 2nd Tristar MPPT is going on a new array, as a smaller 24V system, panels wired to about 50 V.

    Not wanting to jump into a situation with another set of unknowns, I'm staying with what I know.

    I do have another breaker on order, which I will use to switch the 3Kw tristar array to the Classic and then I will have a rock solid comparison, same array into 2 different controllers.

    Today after nearly 3 weeks of clouds, we had sunlight - I finally got through an absorb cycle and into float.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • VicVic Solar Expert Posts: 2,970 ✭✭✭✭
    Re: What size MPPT solar controller

    Hi Mike,

    Just to be clear, a Classic 200 will not be as efficient as most any MPPT CC that is designed for 150 V Max, as the Cl 200 has been optimized for higher string voltages, even if the Cl 200 is operated at a string voltage that is identical to that of the 150 V Max CC. Even with the exact string, as in your upcoming experiment, using the TS's PV string. Am just speaking of the Conversion efficiency, in general, not necessarily the amount of power Harvested.

    When you designed in the Classic 200, am sure knew that you were trading away some efficiency for the Cl 200's unique capabilities, verses the TS, given your engineering background. Just looking at the maximum current capability of a Classic 200 vs the 150, implies that there will be a reasonable efficiency hit in using a Cl 200, IMO. Does not mean that all of the 200's reduced maximum current capability should be assigned to its lower overall efficiency with string voltages identical to those used on 150 V Max CCs), but probably a good part of the max current capability should be assigned to its lower efficiency.

    The Cl 200 probably uses different Inductors, and quite probably higher V FETS, and so on, being optimized for higher maximum string voltages. Am NOT an MPPT CC Designer, just a guesser. If true, these things and others seemingly would make the overall efficiency lower on the Cl 200.

    And, regarding the PV production in cloudy weather, guess that it depends upon just how dense the clouds are, and just where the sun happens to be, and the azimuth differences in the two arrays. The list of variables from one system to another can be fairly long when trying to make useful direct comparisons, even with systems that are side-by-side, again IMHO. FWIW, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • mike95490mike95490 Solar Expert Posts: 8,377 ✭✭✭✭✭
    Re: What size MPPT solar controller
    charlyhors wrote: »
    I'm in the final stages of a solar install - last part is the panels and controller. Although we generally only use 100 AH a day, or even less, I am wanting to build for 200 AH a day eventual capacity in case we decide to replace propane refrigerator with electric (if current 10 yr old frig breaks). Our present setup is a 4 battery bank with 370AH capacity (2 banks of 2 6V 186AH Exides in series, and if we add frig would be going to 6 6V 110AH Trojans, wired in series and parallel, for a 660 AH capacity. Looking at Morningstar Tristar controllers which come in 30, 45, and 60 amp ratings. Your thoughts on which one to buy?

    As this progress, you seem to be needing more and more storage, have you considered 24 or 48V system and powering a small efficient inverter ? Converting the propane fridge will surely take you out of the 12V ballfield.

    Vic -
    http://www.midnitesolar.com/pdfs/Classic1.pdf interestingly enough, does not have any efficiency listings or comparisons with the Morningstar MPPT 60.

    I would expect that a lab test would show 2-5% increased losses as you step up in voltage, as the classics increase voltage, their output ratings decrease, but mostly I suspect, by reason of the FETs capability at higher voltages, not from hundreds of watts of internal losses.

    I do certainly understand that as the array voltages increases above the battery voltage, the losses increase. But do they ? In clear sky, the arrays and controllers track each other quite well - its the poor conditions that the classic falls off at.
    Mike
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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