controllers: one or two?

baja1
baja1 Registered Users Posts: 13 ✭
in Solar Beginners Corner #1
I started out with 8 sp75 panels then got a 110 watt panel. to use the 110 watt panel I bought a morningstar sun saver mppt and stacked it on my original mx60. now I have an identical 110 watt panel so should I ditch the sunsaver controller and put the two 110 watt panels on the outback controller?and should each 110watt panel be paralled with the four 75watt panels in series. both the 75watt and the 110watt panels have the same voltage.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: controllers: one or two?

    If all the panels have the same Vmp you can parallel them up to the limit of the controller's capacity.
    Your eight 75 Watt panels total 600 Watts. The two 110 Watt units added in would be 820 Watts.
    An MX60 can handle 60 Amps on any system Voltage. For 12 Volts that would be about 864 Watts (60 Amps * 14.4 Volts charging). Unless I'm misreading something, it looks like you could parallel all on the MX. Just remember that with more than two parallel connections, each panel must have its own fuse. But the MX60 is an MPPT controller, and can take higher input Voltage than system Voltage so some serial connections between panels may be possible - providing the Imp of the various panels is not too far different. And be sure that the Voc of any such string does not exceed the Vmax in of the controller.

    Some precise panel specs might result in a more precise answer. :roll:

    It's been a long and arduous day here.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
    Re: controllers: one or two?

    i have to correct coot on the wattage as it goes by the nominal voltage unless some of the solar cc engineers here would say otherwise. at 12v and 60a it's 720w. there is a modification that allows the mx-60 to go to 70a and that equates to a 840w capability for 12v. it also does not matter if the pvs are in series or paralleled either because it goes by what the controller can output. now if the battery bank being utilized is a higher voltage then this output capacity will rise proportionally. for instance, at 24v and 60a it will be 1440w and if the modification to 70a is made then it becomes 1680w. the mx-60 can certainly handle the wattage in pvs you have if the cc is modified. i do not know what is involved with the mod or how to do it, but i believe it is a software type mod. maybe somebody else can chime in with either the instructions on how to do it or point you in the right direction.

    of course you can still use the other cc too if you choose not to modify the mx-60.
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  • rplarry
    rplarry Solar Expert Posts: 203 ✭✭
    #4
    Re: controllers: one or two?

    Baja1
    the mx60 can be set to a max of 70 amps by the user. Just go to the set up program and choose the 70 amp option. My mx60 is hooked to 6-190watt evergreen panels (for a total of 1140 watts stc into the the mx60) and will top out at 72.8 amps. The panels can make a few more amps than that but the mx60 blocks the extra amps and limits itself to 70. At 72 amps the mx60 shows that it is making 1012 watts, ofcourse that is determined by the battery voltage at the time, but that is the highest I have seen. Thats 88% of STC, not too bad. Your mx60 should handle your 820 watts no problem.
    Hope this helps
    Larry
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