blowing fuse on external panels

Trailpixie
Trailpixie Member Posts: 191
in Battery/Electrical & Solar
i am using a victron MPPT 75|15 and. keep blowing it's 30 amp fuse. I'm not sure what to look at. I have a 30 foot 10 gauge cable, but the fuse is blowing before I even connect to the solar panels. As soon as I plug it into the connector, the fuse blows.
T@B 360 Black Canyon, 2021 Jeep Grand Cherokee V6, Maryland
(previous 2018, T@B 320 Outback)
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  • AnOldUR
    AnOldUR Member Posts: 1,728
    edited August 2025
    Polarity? SAE ports can be tricky.
    Stockton, New Jersey
    2020 nuCamp T@B 320S * Jeep Wrangler
    60,865 camping miles through the end of 2025

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  • MuttonChops
    MuttonChops Member Posts: 1,939
    Trailpixie said:
    . . . have a 30 foot 10 gauge cable,
    . . .  the fuse is blowing before I even connect to the solar panels.
           As soon as I plug it into the connector, the fuse blows.
    You are saying you have the SAE Port <> a 30-foot extension cable <> a solar panel.
    And the Controller fuse is blowing when the 30-foot extension cable ONLY is plugged in, Yes?

    That sounds like a 30-foot extension cable short.  Even if your SAE Port and solar panel polarity are wrong the Controller fuse would not fail when a fully open extension cable was attached.
    '18 320 S,  pitched axle, 3020HE; PNW based
    TV: '17 Colorado V6 Z71 4x4, Tow Package, GM Brake Controller
    TV: '25 Canyon AT4
    Adventures:  58   Nights:  405  Towing Miles 50,180
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  • Marceline
    Marceline Member Posts: 1,747
    Trailpixie said:
    i am using a victron MPPT 75|15 and. keep blowing it's 30 amp fuse. I'm not sure what to look at. I have a 30 foot 10 gauge cable, but the fuse is blowing before I even connect to the solar panels. As soon as I plug it into the connector, the fuse blows.
    I'm not sure if it will make a difference but when I plug my portable panel into my Victron controller I keep the panel face down or folded when I plug it in, then turn it to the sun afterwards.
    San Francisco Bay Area
    2013 CS-S us@gi
    2015 Toyota Tacoma PreRunner Double Cab
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  • Trailpixie
    Trailpixie Member Posts: 191
    It was reversed polarity. 

     :s [embarassed] 

    Now I have spent two days trying to get their performance up to par. At first I was getting 50 or 60 watts, so I made sure to set the controller with all the key settings from the Battleborn site that match those on the camper's onboard controller. After doing that, my performance went down to 30 watts. I returned the panels to default and they spiked back up to 135 watts. I used the LifePO preset which are nearly the same as Battleborn and the performance went back down to 100 watts. 

    Inconceivable!

    200 watt panels. Clear blue sky. full southern sun exposure. Battery at 73%. That's further off theoretical 200 watt spec than I would have expected. settings in the controller seem impenetrably complex, fussy, and difficult to find. Battleborn site is simplistic and vague. every time I try to manually configure settings, performance drops to 30 watts and stays there. (full sunny day at 2:00 in the afternoon.)

    Any suggestions?
    T@B 360 Black Canyon, 2021 Jeep Grand Cherokee V6, Maryland
    (previous 2018, T@B 320 Outback)
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  • Bayliss
    Bayliss Member Posts: 1,496
    @Trailpixie, what brand/design panels are you using?  Have you tried adjusting the angle of the panels in relation to the sun.  Often, when I do that, it increases/decreases the wattage being sent to the solar controller.
    2019 T@B 320 S Boondock Lite; 2025 Toyota Tundra CrewMax 4x4
    (Alde: 3020; Refrig: Isotherm Cruise 65 Eleg; Battery: BB 100Ah LiFePO4; Solar: Renogy 220W Portable Suitcase w/ Victron SmartSolar MPPT 75/15 Controller; Victron BMV-712 Battery Monitor w/ Shunt; Pwr Cntr: PD-4135KW2B; EMS: PI-HW30C)
    Greg & Marlene (Tucson, AZ)


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  • Grumpy_G
    Grumpy_G Member Posts: 712
    The ratings for solar panels are done with very favorable parameters that are kinda unrealistic. I recently came across a data sheet that listed STC (standard test conditions) and NOC (nominal operating conditions). Differences: 25C vs 46C temperature, 1000W/m2 vs 800 W/m2 solar irradiance resulting in 128W vs 100W output. Solar cells are semiconductors and as all semiconductors perform worse as they get hotter. I've never seen more ~130W from my 200W rated panel either. 
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  • donmontalvo
    donmontalvo Member Posts: 187
    It gets stranger with curved solar panels, like those mounted on T@B rooftops.
    Don Montalvo | Retired Veteran | Full time boondocker
    Camper: nuCamp T@B 320S BBC | 12V 2x100Ah LiFePO4 | 600W Solar
    Tow Vehicle: Jeep JLU Rubicon | 12V 100Ah LiFePO4 | 200W Solar
    https://revkit.com/donmontalvo/ | https://donmontalvo.com
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  • AnOldUR
    AnOldUR Member Posts: 1,728
    edited August 2025
    The most our 310W panel will get us is into the mid to low two hundreds with good sun. But it was still worth the upgrade. The most I saw from the factory panel was maybe 80W. An upcoming project is to move the controller from the factory wheel well position to the front box close to the batteries. I'm hoping that will improve performance.  
    Stockton, New Jersey
    2020 nuCamp T@B 320S * Jeep Wrangler
    60,865 camping miles through the end of 2025

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  • donmontalvo
    donmontalvo Member Posts: 187
    A buddy told me to Google "Lambert's Cosine Law and solar panels":


    Don Montalvo | Retired Veteran | Full time boondocker
    Camper: nuCamp T@B 320S BBC | 12V 2x100Ah LiFePO4 | 600W Solar
    Tow Vehicle: Jeep JLU Rubicon | 12V 100Ah LiFePO4 | 200W Solar
    https://revkit.com/donmontalvo/ | https://donmontalvo.com
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  • elbolillo
    elbolillo Member Posts: 549
    Please post the settings you are using. I have a 220w suitcase panel that I use with a 30' cable and have always had very good charging numbers.
    _____________________________________________________
    Ken / 2023 Tab 400 “La Bolita” (31,000+ miles) / 2024 Toyota Sequoia
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