Help sourcing diodes

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stereoman405
stereoman405 Solar Expert Posts: 56 ✭✭✭✭
in Advanced Solar Electric Technical Forum #1
Having trouble finding a source for spare diodes for my REC 210's. They look similar to the one pictured here:

http://ep.yimg.com/ca/I/wind-sun_2100_42540140

They have 'W9' and 'SB 1240' written on them. Anybody have an idea what these are rated for and what could be a comparable replacement?
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  • lorelec
    lorelec Solar Expert Posts: 200 ✭✭
    #2
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    Re: Help sourcing diodes

    They're a 12A, 40V Schottky diode. The SBR12A45SD1 is a suitable replacement -- $1.22ea from Mouser.

    Marc
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    #3
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    Re: Help sourcing diodes

    For a 210 watt panel the max current is about 11.7 amps.

    You will cook these diodes at max panel current. At about 0.40 vdc forward drop, that will be 4.7 watts of heat generated within diode. The axle leaded diodes just don't have much heat transfer sinking.

    I prefer TO220 package diodes that you can get mounted to something for heat sinking.

    http://www.alliedelec.com/search/productdetail.aspx?SKU=2480840
    http://www.alliedelec.com/search/productdetail.aspx?SKU=5680793
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  • lorelec
    lorelec Solar Expert Posts: 200 ✭✭
    #4
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    Re: Help sourcing diodes

    Depends on what the diodes are being used for and how they're mounted. If replacing the original bypass diodes in the PV, then they should be fine. The panel in question appears to be 27.6v@7.6A with three bypass diodes...so ~2.5A max per diode at 0.40v drop would only be one watt -- which the DO-201 package would have no problem dissipating in free air. To get the full 12A out of the diode, you'd have to heatsink the leads. The data sheet says it's good for a 200degC junction temp, which is pretty darn hot.

    If you're looking for a diode for blocking or some other application, then you would be better off with a tabbed package. Diodes Inc makes their SBR diodes (which tend to have a pretty low Vf compared with other diodes) in TO-220 as well.

    Marc
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  • stereoman405
    stereoman405 Solar Expert Posts: 56 ✭✭✭✭
    #5
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    Re: Help sourcing diodes

    This is just to replace the 3 OEM bypass ones. Switching diodes from manufacturer specs starts getting me a little into uncomfortable territory. :confused:

    If the SBR12A45SD1's are close to that spec I'll just go that route.

    Thanks!
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