Can I Combine These Trackers?

doubledipsoon
doubledipsoon Registered Users Posts: 7 ✭✭
in Off Grid Solar & Battery Systems #1
I have two separate manual trackers with two different brands of solar panels. Tracker #1 has eight [8] Arco 16-2000s (remember those?)- these are rated at 33 watts, open ckt of 21.6v, and rated at 16v. Tracker #2 has four (4) Siemens SR-90 rated at 90 watts, open ckt of 20v, and rated at 17v. They are 30 feet apart, are both wired in parallel for 12v with USE solar cable AWG10. Now, they will ultimately enter into a Xantrex C-60 charge controller, the battery bank, and finally a Exeltech XP1100. There are no fuses between any of the panels, but there are the appropriate breakers between the panels and the charge controller, breakers between the charge controller and the battery bank, and breakers between the battery and the inverter. I've read that you can combine different solar panels IF THEIR VOLTAGES ARE SIMILAR. So, what's the real story?
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    Re: Can I Combine These Trackers?

    With the C60 you just need to be sure you don't have too much voltage drop to be able to charge a 12 volt battery bank, with 16v VMP(I'm assuming that's what your saying) I would wan them very close to the battery bank, even with the small wattage of the array. The voltage will drop some during the heat of the day so you have very little 'head' room.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: Can I Combine These Trackers?
    doubledipsoon wrote: »
    There are no fuses between any of the panels, but there are the appropriate breakers between the panels and the charge controller

    Welcome to the forum.

    I have to say first of all that this is backwards. No fuse/breaker is required between an array and charge controller as no over-current condition can exist there. It can exist in the array when you have more than two panels in parallel, which is the case here.

    What is worse is that just as Photowhit suspects the Vmp of both arrays is too low for a 12 Volt system. By the time you get through the V-drop in the wiring and from increased panel temperature it is doubtful that there will be enough left to reach Absorb much less EQ.

    As for the 16 Vmp being compatible with the 17 Vmp, that technically is not a problem. One Volt difference will not be noticed.

    My advice would be to rewire the arrays for double their Voltage by putting the panels in strings of two. The first one would have four parallel strings (each with its own fuse/breaker) of two in series and a Vmp of 32. The second one would have two parallel strings of two in series (no string fuse/breakers needed if on its own but per-string would be needed if in parallel with the first array) and a Vmp of 34. The difference would then be 2 Volts; higher, but still not a significant power loss.
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