Help with array configuration

solarsquirralsolarsquirral Solar Expert Posts: 54
Hi guys thanks in advance for any pointers. I have 17 she'll sp75. 75 watt panels And a trace c60 controller. How would you recommend the configuration of array strings. I was thinking two strings of 8 and but the controller says max 55vdc. So with a open circuit voltage of 21.7 does that mean I can only have two panels on a string? Another question was breaker size and fuses. Thanks
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  • solarsquirralsolarsquirral Solar Expert Posts: 54
    Specs for panels are. Rated current 4.4/ short c 4.8. 15 amp series fuse
  • Raj174Raj174 Solar Expert Posts: 795 ✭✭✭✭
    Hi solarsquirral,
    What is the battery voltage
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
  • solarsquirralsolarsquirral Solar Expert Posts: 54
    12 volt.
  • VicVic Solar Expert Posts: 3,112 ✭✭✭✭
    edited February 2016 #5

    HI solarsquirral,

    The C-60 is a PWM controller.   For the best efficiency,  the PV Vmp voltage needs to be just a bit above battery voltage.

    SO,  strings of eight will result in far too high of an input voltage to the CC,  and it would FRY.

    You would probably want "strings" of one PV,  ie,  all in parallel,  and there is a limit in the output current that the CC can handle.

    This is the Data Sheet for those PVs,  I believe
    http://www.physics.arizona.edu/~cronin/Solar/TEP module spec sheets/shell installation.pdf

    More Later,   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.
  • solarsquirralsolarsquirral Solar Expert Posts: 54
    So are you saying I should have 17 single strings
  • Raj174Raj174 Solar Expert Posts: 795 ✭✭✭✭
    If the battery were 24 volt you could run 8 strings of 2 panels. You could also do that with an MPPT change controller. However with a PWM controller and 12 volt battery the only way to go without wasting power is wiring the panels in parallel. A lot of wiring I know. An MPPT controller would help that but for that much amperage your looking at several hundred dollars. I believe 6 to 8  amp breaker or fuse should do for parallel connections 
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
  • solarsquirralsolarsquirral Solar Expert Posts: 54
    How many to a string in parallel ?
  • Raj174Raj174 Solar Expert Posts: 795 ✭✭✭✭
    1 to a string, so no strings. Their amps add up and the voltage stays the same. So 60\4.4= 13 panels max
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
  • solarsquirralsolarsquirral Solar Expert Posts: 54
    13 panels max in parallel or 13 panels max for controller
  • Raj174Raj174 Solar Expert Posts: 795 ✭✭✭✭
    edited February 2016 #11
    13 panels max for controller, however read the controller manual, It might be able to shave off the over current. I have not encountered that many panels in parallel and am not 100% sure the controller can't dissipate the extra amps above it's designated amount. The reason more panels would be better is better production in morning, evening and cloudy days, i. e. lower light conditions. 

    One other thing, the array output needs to match the battery bank capacity 
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
  • Raj174Raj174 Solar Expert Posts: 795 ✭✭✭✭
    For example, if the controller is outputting 60 amps then a lead acid battery bank would need to be no smaller than 500AH.
    If it's an AGM bank then something around 300 to 350AH.
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
  • solarsquirralsolarsquirral Solar Expert Posts: 54
    Thanks for the info. The bank is made of four 6v 550ah Wired in series parallel. The cc can Handel 85 amps intermediatly I'm trying to set it up so I get a solid 60 amps flowing during absorb charge.
  • Raj174Raj174 Solar Expert Posts: 795 ✭✭✭✭
    That's great, sounds like that will do the job, good luck
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
  • vtmapsvtmaps Solar Expert Posts: 3,739 ✭✭✭✭
    edited February 2016 #15
    The bank is made of four 6v 550ah Wired in series parallel.
    You could configure those batteries to be 24 volts.  Then you could have 2 panels to a string, and you would have a more efficient and more stable system.  Maybe.

    The reason for the 'maybe' is that your panels have a Voc of 21.7 and two in series would have Voc of 43.4.  That may be too close to the controller max input voltage of 55.  When the panels are cold, before the sun warms them up, they will have a Voc that could get up above 55 volts (depending on your climate).

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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