new solar setup aboard

I have scoured quite a few postings to educate myself but still need to ask the wizards of solar ;
1. How would you combine four KC -130W panels to a Tri-star 45A controller which is charging 3 AGM 165a/h 12v batteries. The run is only about 20 feet to the controller and suspect the bulk charge voltage should be 14v, with float at 13.4v. The issue of wiring one panel through the other confuses me as I read that 30A coming from the final panel through a 10awg wire is too much?? Daisy chain was mentioned??
2. Is it important to have a breaker on the + line just before battery connection or will a 50A fuse suffice?
3. Grounding for lightning may be an issue as we are in Cayman and pretty close to summer lightening shows.
4. Will other forms of charging i.e. ac charger or alternator, upset the controller? Should I disconnect the controller for motoring?

Could find an electrician but yachtties are willing to learn/tight.
Thanks
Jon

Comments

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: new solar setup aboard

    jon,
    i am assuming you wish this at 12v for both the pvs and batteries if i'm reading you right. yes, it is a problem with daisy chaining all of them as by the time you get to the last pv you are up to nearly 30amps with losses occuring before that last pv. in figuring for a single kc130 going that 20ft run it is 2.75% loss with #10. knowing this means 4 seperate runs from each of the pvs using #10 going to the controller works. now for having 2 runs with 2 paralleled pvs on each run you will need #7 to keep the losses the same 2.75%. now paralleling all 4 will need a wire gage of #4 to keep with the percentages. now the question is how are they combined and where? you could use combiner boxes or some other cheaper arrangement with short runs of wire, but that adds to the total wire run and the total losses. to account for this if the extra wire is under 5ft you could take the gage we figured it to work on above and just add a gage to account for the extra length. that #7 wire would become #6 so that you'd have 2 pvs paralleled by 5ft lengths of #6 to be combined and run another length of 20ft with that same #6. there are lots of options and combinations to use and if you wish to do so you could play with the loss calculator here http://www.wind-sun.com/smf/index.php?topic=1477.0
    if you want to have me calculate for a specfic arrangement i can do it for you. just tell me of how you wish to go about it (with combinations of what if any?) and reaffirm wire lengths to be used.
  • BB.BB. Super Moderators, Administrators Posts: 30,494 admin
    Re: new solar setup aboard

    1. There may be a little confusion in the question (at least as I read it). Daisy chain, usually, means that each panel is connected in series. So, 17 vdc and 7.3 amps would be 68 vdc and 7.3 amps. (like batteries stacked in a flashlight).

    For a standard controller, connecting the four panels in parallel would give you 17.6 vdc and 29.56 amps.

    I don't know the Tri-Star 45/60, but from a quick scan of the data sheet it appears to not be MPPT controller. So, even though it appears a person could run four KC-130 panels in series--daisy chain--(125 VDC max input), that it would just waste power (PWM regulated)... The most efficient use of the panels (on a 12 volt battery bank) would be the 4 130 watt panels in parallel.

    Using an MPPT Controller (like the OutBack MX60) would seem to be a good choice here. It can take of 4-6 KC-130 watt panels in series (daisy chain). So only one pair of wires rated to carry ~7.5 amps are required. Max input 125 vdc, can charge battery banks at 12, 14, 36, 48, or 60 vdc at 60 amps max output (or even a little higher than 60 amp--if I recall correctly--read manual?). Will convert the ~4x17.6volts @ 7.39ams into 520watts -10w (overhead) = 14 volts @ 36.4 amps... (vs 14 volts @ 29.56 amps)...

    Of course this is a bit high at STC (standard test conditions--520 watts would be very cool day). Grand Caymans are warm and the actual 4x130 watt power from the panels will proably be closer to 410 watts on a 95 F day...

    Don't need to use MPPT to get the most power of the panels, but can use MPPT to allow series connections of panels to reduce current on wire from solar panels ( ~88 volts DC-open circuit around 7.4 amps). However, this is probably a much more expensive (and larger than needed for 4 130 watt panels) controller than needed.

    Is there another, smaller MPPT controller, that would meet their needs?

    If you already have the Tri-Star, parallel connections of the 130 watt panels with lots of heavy gauge wire (per Niel) are the only
    solution that I see.

    2. You want fuse/breaker as close to the source as possible (battery bank in this case) to protect down stream wiring from shorts. Properly rated DC fuse or breaker is your choice--which holds up better in your environment and if you will carry spare fuses for emergency. If you place the fuse/breaker too far from the battery, it is possible for something to short the wire between the fuse and the battery--causing a dead short with no protection.

    3. We talked a bit about lightning here:

    http://www.wind-sun.com/smf/index.php?topic=1585

    It has been a long time since I looked at boats and their grounding systems... Depending if you have a steel or non-conductive hull, etc. are issues where to connect your ground. Assuming you have a good "sea" ground already defined for your boat, following the recommendations here would be a good start on how to ground your solar PV system:

    http://www.windsun.com/Lightning_Protection.htm

    4. Unless I am missing something, there should be no problems with leaving your solar charge controller connected while motoring. You may have a dropout of your 12 vdc loads (connected to the charge controller) if you are using your charge controller's Low Voltage Load Cut-Off function (loads turned off when batteries are at 10.5 vdc or lower) when you start your engine.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: new solar setup aboard

    The TriStar is indeed a PWM controller and not a DC-to-DC step-down / MPPT controller. Accordingly, the PV array’s nominal voltage must match the battery bank’s nominal voltage (see: http://www.morningstarcorp.com/products/FAQ/#12 ).  Assuming your three AGM batteries are wired in parallel for 12 V x 495 Ah total, you’ll need to wire the four KC-130’s in parallel (17.6 Vmp x 29.56 A Imp) for their connection to the controller.

    If you wire all four modules together at the array and then connect a single cable air from the array to the controller, you’ll need at least #4 wire (TriStar manual, page #16)

    A wiring option that you have would be to connect each PV module separately using #10 AWG THHN wire. The four wire pairs could be connected to a power distribution fuse block used “backwards” as a combiner. Locate this combiner near the controller and run #6 between the combiner and the controller, and use a 10 A fuse for each module (~125% x 8.02 A Isc).

    Check the battery manufacturer’s specs for the correct absorption- and float voltages, and then make the appropriate battery settings (see manual pgs. 12 and 27). Unless the manufacturer specifies otherwise, I’d recommend starting with Battery Type 3 (PWM = 14.35 V, Float = 13.4 V) and EQ set to manual. Make sure to connect the battery sense lines (improves charging voltage accuracy), and, if the battery temperature varies outside of a 75 F to 80 F range, you should also hook up the optional remote battery temperature sensor (provides temperature compensation for battery charging voltage).

    Ample Power may be able to help with grounding recommendations. 

    In general, Morningstar chargers can be wired to batteries connected to other charging sources.

    HTH,
    Jim / crewzer
  • System2System2 Posts: 6,290 admin
    Re: new solar setup aboard

    Many thanks for all the answers.
    It seems I need a combiner/buss sustem to accommodate the wiring from each panel - or, as Neil suggested parallel 2pvs to have 2 runs of 15A each ( using #6 for good measure) and then a #4 from the controller to battery ?
    I will need to read and digest the info a little more so will refer back to the suggestions .
    Are there splashproof combiners available as one never knows when a wave will find its way in.
    Also would you install a battery on/off switch between the controller and battery to isolate when needed?

    Thanks
    Jon
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: new solar setup aboard

    i was searching around for a picture of a terminal block for you before and low and behold patman3 had one in his pics he posted for his ev down in energy use and conservation. hope this link is copied right so you can go there direct. it's the 4th pic from the top i believe. http://www.citlink.net/~pata/solar.html
    with 2 of those terminal blocks in an insulated plastic electrical box you may be able to have a homemade combiner. if you like and if it is convenient you could put fuses there too when the combiner is readily accessible. the ones you need won't be as big as you don't need to combine more than 4 pvs and the main lead to the controller. good luck on the wiring as prices are up.
  • BB.BB. Super Moderators, Administrators Posts: 30,494 admin
    Re: new solar setup aboard

    Regarding switches... There are many poorly designed switches out there and adding more moving parts/connections to a system (especially exposed to salt) is just asking for trouble. Assuming everything is installed correctly, there should be no reason to disconnect the solar charger/controller in normal use--just for maintenance.

    Since you should be fusing everything, I would first look for a good insulated fuse holder (marine grade). And, if you want a quick disconnect, loop some fabric around the fuse body to use as a pull strap (hmm, something non-melting, high temp, long lasting--Kevlar or eq.???). And/or have a fuse puller mounted nearby (with extra fuses) so that you can pull the fuse(s) quickly--if needed.

    The Ample Power link from Jim provided some warnings on rotary type battery bank switches.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: new solar setup aboard

    Water tight / resistant boxes are available, and you might consider other combiners and fuses.

    http://store.solar-electric.com/j606w.html
    http://store.solar-electric.com/16220-2.html
    http://www.bluesea.com/dept.asp?d_id=7463&l1=7463

    The old Perko switch mentioned in Ample Power obviously had a problem. Reading the article suggests to me that Mr. Smead blames the switch’s rotary contacts and not the rotary action. Blue Seas marine battery switches appear to be well-built and certified, especially their heavy duty model.

    http://www.bluesea.com/
    http://www.bluesea.com/dept.asp?d_id=7459&l1=7459
    http://www.bluesea.com/dept.asp?d_id=18015&l1=7459&l2=7492

    I can't think of a reason for putting a switch between the controller and the battery. But, I'm not familiar with your configuration or operational needs. So, if you do, I recommend the wiring sequence be controller - switch - fuse/breaker - battery. This way, the fuse will protect the switch and the controller. Note that the battery voltage sense line, if used, would need its own switch and fuse.

    HTH,
    Jim / crewzer
Sign In or Register to comment.