mixing different panel types/wattages

opticalmike
opticalmike Registered Users Posts: 20 ✭✭
in Solar Beginners Corner #1
I currently have 4- 85 watt LDK 085 P panels (36 CELL) on my fiver charging 4 T-105s 6 volt golf cart batteries. The charge controller is a Chinese WPM 30 amp.
Specs of the LDK (36 cell) Specs of the grape solar 160 watt panels (36 cell)
Vmp 17.3v .......................... 18.5v
Imp 4.93a ........................... 8.65a
Voc 21.6v .......................... 22.2v
fuse 10a ............................fuse 15a
Id like to put 2 of the 85's together in series, so two strings of 85's in series
and run the 160s each by themselves. all terminating in a combiner box on breakers.
add a Midnite kidd charge controller in place of the wpm chinese controller.

How compatible are the above two panels ie are they close enough in voltages??
OR run both charge controllers
Thanx in advance.
mike
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Comments

  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #2
    Re: mixing different panel types/wattages

    Your voltage difference is about 7%, which is outside the conservative 5% band but within the more liberal 10% figure.
    The 85W are the lower voltage, so the effect on the total power output will be minimized.

    But I think you are going it the wrong way by trying to put two 85s in series to get 34.6 volts and then paralleling those strings directly with 18.5V 160 panels.
    You will have to make two panel strings for all of your panels before you can put them in parallel unless you use a CC with two separate MPPT inputs.
    If you have two MPPT inputs available, then you can do just about any combination you want.

    Are you planning to make a 12V or a 24V battery bank from your four 6V units?
    For 24V you will have to put at least two panels in series for any charging at all. The Kidd will not boost voltage.
    SMA SB 3000, old BP panels.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: mixing different panel types/wattages

    Your 30 Amp PWM type charge controller will not handle the additional panels on a 12 Volt system:
    (4 * 4.9) = 19.6 + (2 * 8.6) 17.2 = 36.8
    Otherwise the panel Vmp's are close enough that they could all work in parallel.

    If you go up to a 24 Volts system you would wire the 85's as two strings @ 35 Vmp and the 160's as one string @ 37 Vmp. The Vmp difference as a percentage is even lower then.

    The Kid could use that array either for a 12 or a 24 Volt system.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #4
    Re: mixing different panel types/wattages
    Cariboocoot wrote: »
    If you go up to a 24 Volts system you would wire the 85's as two strings @ 35 Vmp and the 160's as one string @ 37 Vmp. The Vmp difference as a percentage is even lower then.
    Just to be clear... Cariboocoot is saying that if you upgrade your system voltage to 24 volts, you could continue to use your present controller
    Cariboocoot wrote: »
    The Kid could use that array either for a 12 or a 24 Volt system.

    I think Cariboocoot's suggestion to put the panels in strings of two panels in series is good. If I recall correctly, when you asked about this on the Midnite forum, you were only planning to buy one of the larger panels... do you have room for two of them on your fiver?

    One detail that Cariboocoot left out: you will need to put fuses or breakers in each of the strings with the 85 watt panels.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: mixing different panel types/wattages
    vtmaps wrote: »
    Just to be clear... Cariboocoot is saying that if you upgrade your system voltage to 24 volts, you could continue to use your present controller

    Providing it can operate as a 24 Volt controller. Not all of them can.
    I think Cariboocoot's suggestion to put the panels in strings of two panels in series is good. If I recall correctly, when you asked about this on the Midnite forum, you were only planning to buy one of the larger panels... do you have room for two of them on your fiver?

    One detail that Cariboocoot left out: you will need to put fuses or breakers in each of the strings with the 85 watt panels.

    --vtMaps

    Actually the OP mentions two panels and a combiner box with breakers.

    One thing that should be pointed out is that the Kid handling 660 Watts on 12 Volts will be 'clipping' more than is good for it as it is a 30 Amp controller and that much panel could kick out 42 Amps on 12 Volts. This is not desirable.
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  • TucsonAZ
    TucsonAZ Solar Expert Posts: 139 ✭✭
    #6
    Re: mixing different panel types/wattages

    If you have the panels to run them at 24v and a MPPT CC I can see no viable reason not to do so no matter if you have a 12v or a 24v battery bank.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: mixing different panel types/wattages
    TucsonAZ wrote: »
    If you have the panels to run them at 24v and a MPPT CC I can see no viable reason not to do so no matter if you have a 12v or a 24v battery bank.

    The array Voltage is not the issue: charge controller's current ratings are based on their output. As I said, that much panel on 12 Volts could be over 40 Amps and so not suitable for a 30 Amp controller.

    It would be best not to use a 12 Volt system if at all possible.
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  • opticalmike
    opticalmike Registered Users Posts: 20 ✭✭
    #8
    Re: mixing different panel types/wattages

    How about adding one or two of these panels.... 100 watt chinese panels ?? Surely these are close enough to the 85 watt panels I have now.
    Could I run 3 strings of 2 panels per string in series to the combiner box on 3 breakers, then to the kidd. I want to keep my trailer as a 12 volt system as I have a 3000 watt inverter thats 12 volt and
    a trailer full of 12 volt LED'S. What is the ideal wattage of an array to properly charge the 4 T105's or is it more a function of loads.
    100 watt panels
    Vmp 17.5v
    Imp 5.72a
    Voc21.6
    Isc 6.4a
    This would bring me up to 440 watts or 540 watts. I do have a kidd controller on order to replace the chinese PWM controller.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: mixing different panel types/wattages

    A Vmp of 17.5 is close enough to 17.3 to make no difference.

    Then it's a matter of adding up Amps. You've got (4 * 4.93) 19 now, giving you 'room' for 11 more Amps. These panels have an Imp of 5.72 so two more would bring the total to just under 32 Amps. The Kid would still 'clip' occasionally but nothing major.
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  • opticalmike
    opticalmike Registered Users Posts: 20 ✭✭
    #10
    Re: mixing different panel types/wattages
    Cariboocoot wrote: »
    A Vmp of 17.5 is close enough to 17.3 to make no difference.

    Then it's a matter of adding up Amps. You've got (4 * 4.93) 19 now, giving you 'room' for 11 more Amps. These panels have an Imp of 5.72 so two more would bring the total to just under 32 Amps. The Kid would still 'clip' occasionally but nothing major.

    I can get those 100 watt panels in poly or monocrystal which is better?
    thank you for your patience,
    mike
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #11
    Re: mixing different panel types/wattages
    opticalmike wrote: »
    I can get those 100 watt panels in poly or monocrystal which is better?
    thank you for your patience,
    mike

    The difference between the two types is Watts per square area and price; monocrystaline panels take up a smaller amount of space for the same Watts but at a premium. If space isn't an issue go with the lower per Watt cost.
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  • opticalmike
    opticalmike Registered Users Posts: 20 ✭✭
    #12
    Re: mixing different panel types/wattages

    I just got 2 more 85 watt LDK panels, so does this change anything? Would the ultimate way to wire these be in the 3 strings of two panels on 12 volt ? I have the trailer full of 12 volt LEDs and a 3 kW 12 volt inverter. If everything was wired to 24 volt would it require a different inverter? Can I still draw 12 volts off of the battery bank if it we're rejigged as 24 volt?

    Just trying to get the most efficiency.
    Thanx in advance,
    Opticalmike
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  • ILFE
    ILFE Solar Expert Posts: 364 ✭✭
    #13
    Re: mixing different panel types/wattages
    opticalmike wrote: »
    If everything was wired to 24 volt would it require a different inverter? Can I still draw 12 volts off of the battery bank if it we're rejigged as 24 volt?

    Just trying to get the most efficiency.

    If the battery bank is wired as a 24vdc bank, you need to draw off the entire bank, not 1/2 of it, with the inverter.

    I would consider selling the 12vdc, 3,000 watts inverter and buying a 24vdc inverter in its place.

    Now you are talking about more efficiency.
    Paul
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  • opticalmike
    opticalmike Registered Users Posts: 20 ✭✭
    #14
    Re: mixing different panel types/wattages
    ILFE wrote: »
    If the battery bank is wired as a 24vdc bank, you need to draw off the entire bank, not 1/2 of it, with the inverter.

    I would consider selling the 12vdc, 3,000 watts inverter and buying a 24vdc inverter in its place.

    Now you are talking about more efficiency.
    what about all the 12 volt lights in my fifth wheel....
    Probably better to do 12 volt.
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  • ILFE
    ILFE Solar Expert Posts: 364 ✭✭
    #15
    Re: mixing different panel types/wattages
    opticalmike wrote: »
    what about all the 12 volt lights in my fifth wheel....
    Probably better to do 12 volt.

    Pretty much will have to stay with 12vdc, for a camper.
    Paul
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  • Chris
    Chris Solar Expert Posts: 135 ✭✭
    #16
    Re: mixing different panel types/wattages

    You were planning on installing a MidNite Kid CC? if so.....yes I would still wire the penels in in 3 strings of 2......the kids will convert the extra voltage to amps at 12 volts.

    I have 4 X 100 watt panels wired in 2 strings threw a Kid on my Keystone works fantastic!
    (4X T105's wired at 12 volts)
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  • Chris
    Chris Solar Expert Posts: 135 ✭✭
    #17
    Re: mixing different panel types/wattages

    Oh!....and I'd highly recommend getting the shunt, whiz bang jr and battery temp sensor with the kid.....you won't regret it 8)
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  • opticalmike
    opticalmike Registered Users Posts: 20 ✭✭
    #18
    Re: mixing different panel types/wattages

    yes, I have a kidd and whizbang jr on order to update my system. also adding a few more panels.So id' have 3 strings of 2 (85) watt. just over 30 amps...charging the 4 T105's. Are you running two inverters?
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  • opticalmike
    opticalmike Registered Users Posts: 20 ✭✭
    #19
    Re: mixing different panel types/wattages

    does the temp sensor come with the kid or is it an option?
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  • Chris
    Chris Solar Expert Posts: 135 ✭✭
    #20
    Re: mixing different panel types/wattages
    opticalmike wrote: »
    does the temp sensor come with the kid or is it an option?

    It's an option.....but I think it's like 20 bucks
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  • Chris
    Chris Solar Expert Posts: 135 ✭✭
    #21
    Re: mixing different panel types/wattages
    opticalmike wrote: »
    yes, I have a kidd and whizbang jr on order to update my system. also adding a few more panels.So id' have 3 strings of 2 (85) watt. just over 30 amps...charging the 4 T105's. Are you running two inverters?

    I am....I just use the 3000 watt mod sign for large loads like my saws, compresser, shop vac and such.....but the 1500 watt pure sign runs 24/7 wile were at the trailer.

    PS Just over 30 amp is fine with the kid....any extra amps will just be clipped......but this will be beneficial on cloudy days.
    Where in the camper are you mounting the shunt?
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  • ILFE
    ILFE Solar Expert Posts: 364 ✭✭
    #22
    Re: mixing different panel types/wattages
    Chris wrote: »
    PS Just over 30 amp is fine with the kid....any extra amps will just be clipped......but this will be beneficial on cloudy days.

    I like the fact that Midnite openly states it is fine to seriously over PV the Kid, without any issues. As you stated, it will be a plus for cloudy / rainy days.
    Paul
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  • opticalmike
    opticalmike Registered Users Posts: 20 ✭✭
    #23
    Re: mixing different panel types/wattages

    Do you have any pics of your trailer and where your charge controller shunt and inverters are placed?
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  • opticalmike
    opticalmike Registered Users Posts: 20 ✭✭
    #24
    Re: mixing different panel types/wattages

    Here's a pic of the front storage area of my fifth wheel, if I had a smaller inverter I could have room for more batteries, however there's lots of room to mount the shunt and wbjr as well as the kid. Which kid did you get?A marine white or black or wall mount?..
    Chris wrote: »
    I am....I just use the 3000 watt mod sign for large loads like my saws, compresser, shop vac and such.....but the 1500 watt pure sign runs 24/7 wile were at the trailer.

    PS Just over 30 amp is fine with the kid....any extra amps will just be clipped......but this will be beneficial on cloudy days.
    Where in the camper are you mounting the shunt?
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  • Chris
    Chris Solar Expert Posts: 135 ✭✭
    #25
    Re: mixing different panel types/wattages

    I'll snap a few pic's when we go out next week....but I mounted my bussbars, shunt and inverters in the front cubby and I wall mounted the kid right beside my bed. (directly above them)

    Being a travel trailer I had to get creative and pull all the wires that went to the batteries at the hitch up threw the floor.....I then mounted the batts on the ground directly under that compartment.
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