Charge controller suggestions?

SystemSystem Posts: 2,511 admin
I have two 75 watt panels waiting to be installed on my small travel trailer. The trailer is armed with two deep cycle 6v batteries, and a small inverter for my meager 120vac needs. I already have a TM-2020 installed to monitor power.

I live in the inland northwest which means lots of bright sun shine for about 3 months in the Summer, mostly gray for about 4 months in the Winter, and a mix the rest of the time. I boondock for 2 or 3 days at a time, and already know that I can (usually) get by without recharging. I would like the system to maintain the batteries over the Winter.

I'm on a budget and don't anticipate upgrading anytime in the near future. So... is it worth springing for an MPPT controller? If so, any suggestions on which models? The Blue Sky SB2512iX seems like a pretty good way to go because it has built in equalization capability.

I've also been told that I should wire the panels in series to work with an MPPT controller. This makes sense as the resulting voltage will be well above the required battery charging voltage. BUT the panels each output about 21v in direct sunlight without a load. This would be above the max input voltage for the 2512 series.

I have a reasonable understanding of power, but am a complete solar novice.

Any suggestions or feedback would be appreciated.
Thanks!

Comments

  • mike95490mike95490 Posts: 7,874Solar Expert ✭✭✭✭
    Re: Charge controller suggestions?

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

    True MPPT, 75V max input, 200W output to 12V batteries. Should work all winter (what are your low temps? - what is controller spec?) to keep idle batteries topped off.
    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 ,

  • System2System2 Posts: 6,290 admin
    Re: Charge controller suggestions?

    Is the Morningstar controller significantly better than the Blue Sky? Is the efficiency the deciding factor? The Blue Sky has higher amperage capabilities and several additional and useful features for about the same price.

    It would be great to see a good comparison between these products.

    On edit: Low temps around here are usually around 0F. The panels are Siemens, nominally rated at 17V & 4.4amps.
  • Solar GuppySolar Guppy Posts: 1,959Solar Expert ✭✭✭
    Re: Charge controller suggestions?

    The MorningStar is more efficient ( 92% vs 97% ) , Allows upto ( 3 ) 12V nominal panels in series ( 75 Voc max ) much better Mppt tracking has a load output and can be monitor via a PC, its is less amps, but for your system, you could still add another panel before that would be a concern.
  • icarusicarus Posts: 5,108Solar Expert ✭✭✭✭
    Re: Charge controller suggestions?
    billyw wrote: »
    I have two 75 watt panels waiting to be installed on my small travel trailer. The trailer is armed with two deep cycle 6v batteries, and a small inverter for my meager 120vac needs. I already have a TM-2020 installed to monitor power.

    I live in the inland northwest which means lots of bright sun shine for about 3 months in the Summer, mostly gray for about 4 months in the Winter, and a mix the rest of the time. I boondock for 2 or 3 days at a time, and already know that I can (usually) get by without recharging. I would like the system to maintain the batteries over the Winter.

    I'm on a budget and don't anticipate upgrading anytime in the near future. So... is it worth springing for an MPPT controller? If so, any suggestions on which models? The Blue Sky SB2512iX seems like a pretty good way to go because it has built in equalization capability.

    I've also been told that I should wire the panels in series to work with an MPPT controller. This makes sense as the resulting voltage will be well above the required battery charging voltage. BUT the panels each output about 21v in direct sunlight without a load. This would be above the max input voltage for the 2512 series.

    I have a reasonable understanding of power, but am a complete solar novice.

    Any suggestions or feedback would be appreciated.

    Thanks!

    A BS 2512ix CANNOT take 12 volt panels wired in series at 24 vdc. The max voltage for the 2512ix is less than the Vmax of a 24 vdc string. You have to look carefully at the ix specs. I made the same mistake and while I like the controller and it gives a good mppt boost, I would have really liked to have wired my strings at 24vdc.

    Tony
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Charge controller suggestions?

    tony is correct on the use of that controller being only for 12 pvs in parallel. not all mppt controllers have downconversion capability to allow for pv series connections. it is still quite usable as an mppt controller using paralleled 12v pvs though. if you'd still like to place the pvs at a higher voltage potential then you can use the morningstar mppt controller http://store.solar-electric.com/mosumpsochco.html as it will downconvert for a few dollars more. whatever you decide to do please get a battery temperature sensor to properly adjust charging voltages.
  • westbranchwestbranch Posts: 5,087Solar Expert ✭✭✭✭
    Re: Charge controller suggestions?

    I am not familiar wiht the specifics of that BS CC, I presently have a BS2000e. PLEASE NOTE the max amperage rating they show as 25 amps max 20 amps normal rating...but they use the Isc amperage so that in reality the functional (amperage) rating is lower than advertised...please read the specs over carefully. I believed I could use the 2000e with 3 panels but not so when reading the fine print... buyer beware, but a good MPPT charger... now upgrading to an MX 60...:D

    Eric
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • System2System2 Posts: 6,290 admin
    Re: Charge controller suggestions?

    OK! I read the specs before, but apparently didn't "read" them. The fact that I can add another similar (12v) panel is major (despite my earlier claim that I probably wouldn't). I must have misunderstood the Morningstar documentation. I am also very thankful for the clarification on the Blue Sky unit. Thanks so much for that bit of information!

    I'm leaning heavily toward the Morningstar MPPT CC now. One last question... everybody here seems to be on the MPPT bandwagon in general. Are the much cheaper non-MPPT CCs even worth looking at? They are after all "way less expensive"!

    What a great resource this forum is! Maybe there's more to the Internet than just porn after all. ;)
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Charge controller suggestions?

    standard pwm controllers work fine if you can't swing the extra $ right away, but you won't recoup some of the wasted energy like an mppt will. they are much cheaper per amp than mppt ccs, but we think of how much that wasted power cost us in the first place. many pwm ccs are used and on ebay and with some people upgrading their systems the old cc often goes on the open market to reap back some of their costs. some keep them for spares to an mppt cc.
    as to the morningstar controller it will work up to 200w (about 15a out) for 12v battery systems and 400w (about 15a out(oops sorry i fixed)) for 24v battery systems. for reaping any current back then you don't wish to operate the cc at 15a input, but something smaller such as 12a so when it mppts it has room to add to the original input amps.
    understand that i don't want you to go straight into anything until you have read and understood all you need to know and what you may require in a system. we make recommendations, but please do follow up on us and be sure as this will be your decision and your money invested. for all i know you may have need in the future to expand and that means invest in a much larger cc. read as much as you can to get a better grasp as inputting the controller max output rating (3 12v pvs at 65w each may do this) and at the same time if you had 2 130w 12v pvs it would be overmaxed both figured for 12v battery systems which is the same as the cc output voltage set for 12v. a 24v battery system would change that so i can't emphasize enough for you to read as much as you can and get a better understanding of what you are doing and want.
    as some have said here, don't do a ready, fire, aim.
  • Solar GuppySolar Guppy Posts: 1,959Solar Expert ✭✭✭
    Re: Charge controller suggestions?
    niel wrote: »
    as to the morningstar controller it will work up to 200w (about 15a out) for 12v battery systems and 400w (about 30a out) for 24v battery systems.

    Niel, just a small correction, the MS unit is 15amps rated continuous current, regardless of the voltage. The 12V to 24V is were the wattage doubling comes

    For the OP, in this price/power range, there is no better controller and I have tested just about everything on the market in my lab w/solar sources
  • mike95490mike95490 Posts: 7,874Solar Expert ✭✭✭✭
    Re: Charge controller suggestions?
    niel wrote: »
    . a 24v battery system would change that so i can't emphasize enough for you to read as much as you can and get a better understanding of what you are doing and want.

    I first thought of a 24V system, but this is for a trailer, and all the electric goodies are likely 12V, not obtainable in 24V. So the MorningStar MPPT would be close to maxed out in a 12V configuration. It's got a warranty so run it to it's limit. It's supposed to throttle itself back to safe conditions.

    But, the next step up in controllers, will likely have much higher overhead losses, and would need several more panels to be worthwhile.

    And then there is the long standing Trace/Xantrex C-40 (non-MPPT) which is a real workhorse, but you won't reap the benefits of MPPT's extra magic power, and will always give less power than the panels are rated for.
    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 ,

  • System2System2 Posts: 6,290 admin
    Re: Charge controller suggestions?

    Great info!

    And yes, my trailer is 12v. I think I'll go with the MorningStar MPPT controller.

    Would I be asking for trouble if I eventually added a third 75 watt panel?
  • mike95490mike95490 Posts: 7,874Solar Expert ✭✭✭✭
    Re: Charge controller suggestions?
    billyw wrote: »
    MorningStar MPPT controller.
    Would I be asking for trouble if I eventually added a third 75 watt panel?

    Most of the MPPT controllers will "throttle back" when they reach their limit. * I don't * know if the morningstar does or not, maybe someone with one can state their experience.
    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 ,

  • Solar GuppySolar Guppy Posts: 1,959Solar Expert ✭✭✭
    Re: Charge controller suggestions?

    The MS controller is output current limited, you can run them of unlimted DC supplies if you like, you will only get the rated 15 amps output.

    I ran 260 watts of PV and also 390 watts of PV in the 12V configuration, no issues what-so-ever
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Charge controller suggestions?

    as mentioned the controller will output the 15amps, but if you intend on going a 3rd pv (the expansion i mentioned) then either get 2 of the morningstar 15a mppt cc or 1 larger mppt because you aren't leaving any headroom for the extra current the mppt would've recovered. in a case of using 1 ms 15a mppt with the 3 75w pvs you not only will lose the extra mppt current, but also a portion of the straightup pv current available. one would be better off with using just a straight pwm cc rated 15a rather than 1 15a mppt cc with that much pv current available as both will lose the current over 15a with the straight pwm cc being cheaper. mind you i'm not recommending that you to go to a straight pwm cc here, although you could do so. the idea is not to have wasted current and thusly not to have wasted power with consideration for cc costs. mppt cc recover some of the wasted power and you'd throw it and more away as you are undersizing with the 3 75w pvs as these pvs will output above 15a. the cc will be fine with this over current, but you will lose the current just the same that costs so dearly in pv costs.
    i hope i'm not talking in circles here or confusing you so i'll stop with a recommendation that you allow about a 25% headroom between the input and output on mppt ccs so that you can recover up to 25% of the current at times.
    example for mx60 48a (in) x 1.25 = 60a(out). nec comes into play, but even if it didn't this is good to allow for the extra recoverable current mppt affords.
  • Solar GuppySolar Guppy Posts: 1,959Solar Expert ✭✭✭
    Re: Charge controller suggestions?

    Three 75 watt panels will almost NEVER reach the current limit on the MS controller ( 15amp), the 225 watts is when the panels are at 25C and the Sun is straight onto the panels ( no angles ), this almost never happens, would have to be in VERY cold weather and the panels angled directly to the sun angle on the horizon.

    15 amps into a 13.5V load is about 210 watts on the input side, once in while the unit may current limit, but it will be very rare
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Charge controller suggestions?

    ok in all fairness for those pvs at 4.4a each i'll go along with it, but it is a borderline application being near the max with 3 and i don't like borderline i guess. i certainly don't feel as sg does that they will never reach the max., but even if it does hit the max it won't be for too long. i hope you get the general ideas of what i was saying and what you get will ultimately depend on you as to how far you want to go and with what.
  • System2System2 Posts: 6,290 admin
    Re: Charge controller suggestions?

    Thank you one and all for your input. I was able to follow and understand pretty well. In my case, the (2) panels were free and I'm just trying to find the best way to put them to use. I "may" be able to "negotiate" on a third panel later. That's the only reason I asked that question.

    On a side note, the roof of the travel trailer is slanted to each side allowing water run off. I plan on installing the 2 panels one on each side staying with the roof angle. Thus they will be about 15-20 degrees off from each other anyhow. If I add a third panel it will be angled with one of the originals. So best case scenario would be two panels aimed directly at the sun with one panel off a little.

    Once again, THANKS for the awesome feedback!
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Charge controller suggestions?

    all of your pvs should face south or as close to south as you can manage with an elevation angle roughly about your latitude or, as some like for better winter collections, your latitude +15 degrees. saying you will have a pv on each side of the roof tells me they aren't being optimally mounted.
  • BB.BB. Posts: 27,788Super Moderators admin
    Re: Charge controller suggestions?

    Also, if you are forced to have panel sets at angles to each other and you are using them in series strings... Make sure that you don't split a string between E/W/S facing sets...

    For example, if you have one panel facing west, and two facing east in a three panel string--the west facing panel will have low current in the mornings compared to the east facing panels--and it will either drop the current or the voltage of that string in the morning (and--same thing in the after noon).

    So, if you have, for example, two strings, mount one string facing east and the other facing west, and you can parallel both strings to one MPPT controller--the Vmp of the two alternate facing strings will be close enough (even though they are receiving different amounts of sun) that you will not loose much energy having them paralleled to one controller (vs the costs of two controllers, and the additional losses of running two controllers).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Posts: 7,874Solar Expert ✭✭✭✭
    Re: Charge controller suggestions?
    niel wrote: »
    all of your pvs should face south or as close to south as you can manage with an elevation angle roughly about your latitude or, as some like for better winter collections, your latitude +15 degrees. saying you will have a pv on each side of the roof tells me they aren't being optimally mounted.

    Heck, the roof on my house faces west, I'd love to face the panels south, but on an RV, you have to work with what's there, in the space thats there.
    We need Mr Möbius to make us a roof that always faces the sun, and won't drip in the living room.
    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 ,

  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Charge controller suggestions?

    yes, i'm aware of your situation mike. you make due with what you can and you do suffer a loss for it. it still does not change the fact that the most solar radiation is from the south (editted to add)> for the northern hemisphere.
  • System2System2 Posts: 6,290 admin
    Re: Charge controller suggestions?

    I understand that max power is achieved by the most direct exposure to the sun. However, I use my trailer to camp and play, mostly in wooded, mountainous areas. The solar aspect is secondary. I went into this assuming that an MPPT controller would help me get the most from my permanently mounted panels which may or may not be facing the sun. In fact, in particularly warm weather I will most likely opt for a shaded location. Is this a bad thing?

    My main goals are keeping my two 6v batteries topped off when the trailer is not being used, and then being able to extend my camping time without needing to use my generator.
  • BB.BB. Posts: 27,788Super Moderators admin
    Re: Charge controller suggestions?

    In shade, you will produce virtually 0% of your panel's rating... Some folks have wired several panels on an extension cord (put several panels in series to jack up the voltage and drop the current with an MPPT charge controller--and the extension cord can use standard wire guage (12 or 10 awg extensions are available)--and put the panels in the sun while the RV is parked where ever... Of course, this becomes a security issue... Even if you can lock them to a post, vehicle, etc... It is still not that difficult for somebody with a pair of bolt cutters to steal them.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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