Newbie here- Question about Sharp 80w PV panel

System
System Posts: 2,511 admin
in General Solar Power Topics #1
Hi all. Nice forum here.

I was on a hunting trip this past Monday, and my buddy's truck battery went dead. Well we got the truck jump started. He was going to let it run for a bit, but I offered/decided to use my 80w Sharp PV panel to try to charge the battery while we went hunting that afternoon.

Big mistake. :(

The instant I hooked up the panel to his battery, it sparked, and my panel started smoking from the junction box. I was careful to hook it up with the correct polarity, so i'm not sure why it did that, but anyway it happened. After that, my panel wouldn't charge anything. Luckily, we were leaving on Tuesday, so the batteries in my trailer got us through the rest of the trip without needing any more juice.

When I got the panel home, I took it apart and noticed the diode on the negative side was melted. I saw a place where you could order new diodes, but are they really necessary? I use the panel with an ICP CC20 charge controller to charge my GC-2 batteries that power my tent trailer. I only use the one panel.

Any harm in just leaving the diodes out of the junction box? I cut them out and snipped the bridging wire and the panel currently puts out 4.3 amps (tested it on the trailer today).

Thanks for any advice/help.

Matt
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Comments

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #2
    Re: Newbie here- Question about Sharp 80w PV panel

    With just the one panel, and the charger has reverse current protection in it, I don't see why you need the diode. (I'm sure someone will tell us if I'm wrong however!)

    The bigger question is why did it fry when you attached it to the truck battery?

    Was the truck running when you connected it to the battery?

    Hmmm?

    Tony
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: Newbie here- Question about Sharp 80w PV panel

    Ole,

    There are typically two types of diodes... One to block reverse current (if directly connected to a battery, a solar panel will slowly discharge the battery at night--if there was no solar charge controller connected in series).

    The others are bypass diodes--these allow a shaded panel (or a partially shaded panel) to be bypassed the current from other series connected panels in a string... Such as 4x12 volt panels in series charging a 12 volt battery with an MPPT solar charge controller... If one panel is shaded, the other three will still generate the same amount of current, but at 36 volts (instead of 48 volts).

    It sounds like you fried the bypass diode(s) if you could just cut them out of the circuit and the panel works OK (normally, I would guess this is because the solar panel was connected "backwards" to the battery, and there was enough charge left to over-current the diode).

    If so--then you really do not need the bypass diodes on a single panel setup (assuming "12 volt" panel and 12 volt battery bank). Just clean up any residue from the area using alcohol.

    If the blocking diode fried (and failed shorted), you probably would need to replace it with a length of copper wire (in case the diode fails open later). If you have a charge controller between your panel and your battery (and checking the charge controller spec. says that it does not need a blocking), then the wire jumper replacing the blocking diode should be fine.

    Use Rosin Core solder and/or soldering paste (not acid) if you do any soldering... And clean with solvent (like alcohol) to limit corrosion later.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #4
    Re: Newbie here- Question about Sharp 80w PV panel
    BB. wrote: »
    Ole,

    There are typically two types of diodes... One to block reverse current (if directly connected to a battery, a solar panel will slowly discharge the battery at night--if there was no solar charge controller connected in series).

    The others are bypass diodes--these allow a shaded panel (or a partially shaded panel) to be bypassed the current from other series connected panels in a string... Such as 4x12 volt panels in series charging a 12 volt battery with an MPPT solar charge controller... If one panel is shaded, the other three will still generate the same amount of current, but at 36 volts (instead of 48 volts).

    It sounds like you fried the bypass diode(s) if you could just cut them out of the circuit and the panel works OK (normally, I would guess this is because the solar panel was connected "backwards" to the battery, and there was enough charge left to over-current the diode).

    If so--then you really do not need the bypass diodes on a single panel setup (assuming "12 volt" panel and 12 volt battery bank). Just clean up any residue from the area using alcohol.

    If the blocking diode fried (and failed shorted), you probably would need to replace it with a length of copper wire (in case the diode fails open later). If you have a charge controller between your panel and your battery (and checking the charge controller spec. says that it does not need a blocking), then the wire jumper replacing the blocking diode should be fine.

    Use Rosin Core solder and/or soldering paste (not acid) if you do any soldering... And clean with solvent (like alcohol) to limit corrosion later.

    -Bill

    That's what I figured happened. (accidentally hooked it up backwards) Even though I hooked (according to the notes on the wires) the negative to the negative post on the battery, and positive to positive, I'm thinking perhaps the wires were mis-marked. :confused: I didn't have my voltmeter with me on the trip, so who knows for sure what happened.

    I'll probably end up putting some kind of an inline 7.5A fuse in one of the wires, just in case something stupid like this happens again.

    Next time i'll just have my buddy let his truck run for a while. :p
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: Newbie here- Question about Sharp 80w PV panel

    yes, fusing is a very good idea. i'm going with it being a blown blocking diode as the bypass diode if blown wouldn't stop the operation of the pv. if a controller stops reverse current at night then forget about the diode, but if reverse leakage current occurs then replace the diode.
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