Help with Solar system

interspec
interspec Registered Users Posts: 8 ✭
in Solar Beginners Corner #1
Hi all new to this and was hopping i can get info on the best solutions

Senario, currently have 1 x 245 watt Canadian solar mono panel, NomV=30.2V, OC=37, Current 8.43Amp and this panel is in place on 30 Amp morning-star MPPT solar charge controller with 2 x 12VDC deep cycle battery in series and system voltage of 24VDC, 205AH capacity

Query,

I just bought 2 x 125watt panels, NomV=24.76, OC= 30.2, Current 5.23Amp, and would like to incorporate these PVs my system the most efficient method ? can you advise the best option for this im a newbe so your ideas would be most greatfull
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #2
    Re: Help with Solar system
    interspec wrote: »
    Senario, currently have 1 x 245 watt Canadian solar mono panel, NomV=30.2V, OC=37, Current 8.43Amp and this panel is in place on 30 Amp morning-star MPPT solar charge controller with 2 x 12VDC deep cycle battery in series and system voltage of 24VDC, 205AH capacity

    Does MorningStar make a 30 amp MPPT charge controller?
    I just bought 2 x 125watt panels, NomV=24.76, OC= 30.2, Current 5.23Amp, and would like to incorporate these PVs my system the most efficient method ? can you advise the best option for this im a newbe so your ideas would be most greatfull

    Next, a Vmp(nominal) 24-30 volt panel cannot charge a 24 volt battery bank. You need ~35-40 volts Vmp(std) with a PWM charge controller... Or Vmp as high as ~100 VDC with a higher end MPPT charge controller.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • interspec
    interspec Registered Users Posts: 8 ✭
    #3
    Re: Help with Solar system

    Not sure how this helps me yes morning star have a 30amp controller cos i have one ??? purchased from HEPV in Canada

    can you give me a wiring method to resolve this issue ? can i do parallel in the 125watt and series with the 250 watt ???
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Help with Solar system

    Welcome to the forum.

    Well to start with that one panel won't properly charge a 24 Volt system. Maybe you've already noticed that. Its Vmp of 30 is too low; after V-drop from the panels heating up and wiring losses the amount of Voltage that gets to the battery will be lower than what is needed charge it. An MPPT controller will not make up the difference.

    Your new panels if put in series would provide enough Voltage, but not enough current on their own. There is no way for all three panels to be used on one controller and produce acceptable charging.

    My advice would be to ditch the 125 Watt panels and buy a match to the 245 you already have. Put the two of them in series on the MPPT controller. That should give you 15 Amps peak current (7% rate) and high enough Voltage to achieve 28.8 Absorb and even 31 Equalize if needed.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: Help with Solar system
    BB. wrote: »
    Does MorningStar make a 30 amp MPPT charge controller?

    Yes they do, Bill: http://www.solar-electric.com/morningstar-tristar-ts-mppt-30.html
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  • interspec
    interspec Registered Users Posts: 8 ✭
    #6
    Re: Help with Solar system

    please note that the system has been running with 250Watt panel with the voltage as previous described and fitted buy and installer this has charged and ran the exterior lighting for 8 months without issues ? and its not at 30-40VDC the installer would know this right ? only looking to add panels for additional capacity to use water heating element.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: Help with Solar system
    interspec wrote: »
    can you give me a wiring method to resolve this issue ? can i do parallel in the 125watt and series with the 250 watt ???

    You do not want to do this (put the panels in series) due to the Imp difference: the 245 Watt panel will be limited to the current of the 125 Watt ones. In other words it will drop to (30.2 * 5.23) 158 Watts equivalent.
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  • interspec
    interspec Registered Users Posts: 8 ✭
    #8
    Re: Help with Solar system

    its already been running with one panel with acceptable charging ? 8 months no we cant ditch 125watt panels this is a non proft project for a school, your comments are totally opposite from installers and suppliers in Canada so now i have no idea whats true ?
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  • interspec
    interspec Registered Users Posts: 8 ✭
    #9
    Re: Help with Solar system

    why cant i put the 2 x 125watt in parallel and the 250 watt in series ?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: Help with Solar system
    interspec wrote: »
    please note that the system has been running with 250Watt panel with the voltage as previous described and fitted buy and installer this has charged and ran the exterior lighting for 8 months without issues ? and its not at 30-40VDC the installer would know this right ? only looking to add panels for additional capacity to use water heating element.

    Nope.
    Installers can be, frankly, morons.
    You think it has operated without issues but in reality the issues just haven't shown up yet. The battery is only being brought up to whatever Voltage the panel can manage, which will not be 100%. What's more the mere 8 Amps current is not sufficient for 200+ Amp hours of battery; that's a 3.4% charge rate at most, which is maintenance level. What you are doing is running on the capacity of the battery, which is slowly going lower due to the chronic deficit charge. One day this will show up as no power capacity.
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  • interspec
    interspec Registered Users Posts: 8 ✭
    #11
    Re: Help with Solar system

    its only being loaded with 3 amp its led lighting at present, ok points taken thnx
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  • interspec
    interspec Registered Users Posts: 8 ✭
    #12
    Re: Help with Solar system

    sorry i made an error its 105AH capacity
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #13
    Re: Help with Solar system
    interspec wrote: »
    why cant i put the 2 x 125watt in parallel and the 250 watt in series ?

    I explained that: you will lose a significant amount of power from the 245 Watt panel due to current limiting. Essential with all three in series you'd get (125 + 125 + 158 ) 408 Watts and about 13 Amps current maximum (6% rate).

    Why should you listen to me? Because I fix systems that are wrong. Lots and lots of them. Too few panels, too many batteries, wrong Voltages, incorrect wiring ... got to be hundreds of systems by now. Maybe thousands.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #14
    Re: Help with Solar system
    interspec wrote: »
    sorry i made an error its 105AH capacity

    Wow. That's a BIG difference. Changes the current demands and peak charge rates by a factor of 2.
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  • interspec
    interspec Registered Users Posts: 8 ✭
    #15
    Re: Help with Solar system

    so basically best idea is to setup the 2 125wat on there own system, and cant use them with current system correct ?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #16
    Re: Help with Solar system
    interspec wrote: »
    so basically best idea is to setup the 2 125wat on there own system, and cant use them with current system correct ?

    Not without considerable loss of power from the 245 Watt panel.
    However, that will not correct the low Voltage of the large panel. What you would have in effect is all panels contributing current up to the Voltage where the 245 Watt passes its at-battery Vmp, then the two 125 Watt panels would be left to finish the charging to the appropriate Absorb level. They may not be sufficient for that. And since the Vmp on the smaller panels appears to be 24 they would need to be in series and again on an MPPT controller to make best use of them (otherwise you'd only get the Imp rating of a single panel).

    When you look at the need for spending another $225 to get a Morningstar 15 Amp MPPT in order to realize an additional 8 Amps charging ... My original suggestion of buying a matching 245 Watt Canadian solar and putting it in series with the one you already have on the controller you already have looks much better, doesn't it?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #17
    Re: Help with Solar system

    Ah:
    NOTE: This brand new model will be available for order by the middle of April, 2014. If you have any questions, please give us a call or [EMAIL="sales@wind-sun.com?subject=TS-MPPT-30%20Inquiry"]email us[/EMAIL].

    This controller comes with a battery temperature sensor included.

    If you have the panels--I would probably try the 245 panel in-series with the two 125 watt panels (125 watt panels in parallel).

    Measure the voltage across each set of panels, and the operating current (in full sun, with less than full charge battery bank) and see hot it performs.

    But, as Marc types, you would be better off getting a second 245 panel and placing it in series with the original panel (assuming Vmp/Imp are same/very similar).

    It is a big problem trying to mix/match panels, controllers, and battery banks. It is not usual to see somebody gets a handful of panels cheap, and then find out they need to spend $300-=$500+ for a second MPPT controller to make it all work.

    In this case, if you get the second 245 watt panel, you would still need a second new MPPT controller for the pair of 125 Watt panels in series.

    You could put the pair of 125 panels behind a C40 Xantrex PWM controller, but you would only get around ~73% of the "available" 250 watts from those panels--But a "less expensive" PWM controller may at least not hurt your wallet as much and you still get a fair amount of power from those "extra panels".

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #18
    Re: Help with Solar system

    Flog the 125 Watt panels.
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