MPPT Controller-Panel Power Question

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System
System Posts: 2,511 admin
in Solar Beginners Corner #1
I just ordered a Xantrex XW-SCC 60Amp controller from solar-electric.com and am awaiting delivery of four solar panels from another place. The panel are rated at 295watts (Vmp=36.4,Imp=8.11) and I plan on wiring pairs in series to make 72volts and paralleling the two strings to get 16.2Amps. My battery bank is for 12volts, so I'm limited to about 864watts output from the controller (14.4v x 60amps). Now my question is: will it be a problem if the solar panels are able to supply more than the 864watts the controller is limited to outputting into my 12volt battery bank? That is...can they damage the controller by being able to supply more power than the controller is rated for at my battery voltage? Or will the controller just tap whatever amperage it needs to output and ignore any excess available? Thanks...
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
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    Re: MPPT Controller-Panel Power Question

    Generally, MPPT controllers will throttle themselves to stay within their safe limits (watts, heat, etc.) so you are only wasteing your excess PV for an hour each day. However, after the peak period, you will harvest more power the rest of the day.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • System2
    System2 Posts: 6,290 admin
    #3
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    Re: MPPT Controller-Panel Power Question

    Thank you for relieving my concern on overpowering the input to the controller. Now, if you please a second question. I currently have a 12Kw propane generator that feeds an IOTA DLS-75 marine battery charger that feeds my battery bank of six golf-cart batteries wired in series-parallel to yield 12.7volts. The inverter input is also in parallel with the battery bank. I'd like to feed the same battery bank with my soon to be received Xantrex XW-SCC 60Amp controller. Can both chargers' outputs be left connected to the same battery bank (they'd be in parallel) at the same time without problems? How would either react to the other if both were active at the same time? If needed, an SPDT switch or relay would have to be rated for at least 75amps DC to survive the switchover, so is either routinely available online? Thanks...
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
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    Re: MPPT Controller-Panel Power Question

    Generally, parallel battery chargers are OK. Hopefuly, you have some other loads on the genset besides the little charger ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • silvertop
    silvertop Solar Expert Posts: 155 ✭✭✭✭✭
    #5
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    Re: MPPT Controller-Panel Power Question

    I just looked in the XW owner's manual and on pg2-2 it states "CAUTION: EQUIPMINT DAMAGE . The PV array voltage must never exceed150 V OC under any conditions. The array I sc must not exceed the 60 A input current rating of the XW SCC at any time ." I know the XW has over-voltage / current protection prompting a warning and fault message and shuts down as a protective measure.
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