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2024 Tab 400 solar controller fuse location

benpcbenpc Member Posts: 6
in Battery/Electrical & Solar
Hi all, new owner looking to disconnect my lithium battery for the winter by following Nucamps instructions to turn off the batt disconnect and pull the solar controller fuse (https://m.youtube.com/watch?v=UrtTgBBQOK8)

What I’m wondering is… where can I find the solar controller fuse on my 2024 Tab 400 BD? I don’t see anything relevant on the panel. Should I look for it under the bed somewhere? 

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Comments

  • HoriganHorigan Member Posts: 805
    It's usually an inline fuse in the wires going to the solar controller under the bed.  The controller looks like this.
    Victron Energy SmartSolar MPPT 7515 Retail image number 0
    Inline fuses look like this.
    Sponsored Ad - MulWark 2 Pack 10 Gauge Tinned Copper Marine Wire Waterproof IP67 Inline Fuse Holder Pigtail Blade Fuse Blo
    Rich
    2019 T@b 400
    2013 Toyota Highlander 3.5L V6
    2025 Toyota Highlander 2.4L Turbo
    Bellingham WA
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  • benpcbenpc Member Posts: 6
    Right on, thanks! I’m inferring that between the disconnect switch and this fuse, all the parasitic drains on the battery should be eliminated and it can just hang out for the winter. 
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  • pthomas745pthomas745 Administrator, Moderator Posts: 4,347
    Turning off the battery disconnect stops the "parasitic" drains of the trailer. There is little need to pull the fuse on the solar controller, since the "drain" from the controller is down in the millivolts.  Why NuCamp says to do this is a mystery. The battery itself, even with every possible "parasitic drain" turned off, will still "self-discharge at about 3-5 percent a month. 
    But, if you must: there are three fuses that are connected to the solar: one is on the positive cable in from the solar panels on the roof.  You can find that one very close to the controller.  There is another fuse on the line between the solar controller positive cable that goes to the battery switch.  You just have to sort out which fuse is which: there is another battery fuse for the trailer wiring near there, also.
    The third fuse is on the bottom of the Victron, which is a "reverse polarity fuse".  It is a real pain to get out of the unit, and usually will require removing the unit from the wall and using some gentle force with some pliers to get it out.  
    The 400 solar controller locations are mentioned in this thread, so hopefully this thread will help  you find it.
    And, last: if you start pulling all these fuses, remember that the fuse "replacement" order for the Victron controller has to be: connect the fuse between the battery and the solar controller first, and then connect the fuse between the controller and the solar panel positive.  The Victron has to sense the battery state of charge for a few moments before the solar kicks in.


    2017 Outback
    Towed by 2014 Touareg TDi
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  • benpcbenpc Member Posts: 6
    Oh interesting! It’s probably worth staring that my objective here is to store the unit during the New England winter (read: below freezing for days / weeks at a time). And while the solar panel will have a clear view of the sky, it’s right up against a building to the south so it will never get direct sun. 

    I talked to my rep at NuCamp, and his advice was to just turn the battery heater on (single 100ah battery) and let the solar keep things topped off. I think I’m piecing together that the heater only kicks as the battery temp approaches freezing, and keeps the battery in an optimal state to charge. Given that Battleborn says that you can just completely disconnect the battery and let it sit in cold temperatures, I think I’m picking up that the battery heater over the winter is so that the battery can charge from the solar, and the solar is so that the battery can run its heater, so that it can charge from the solar, so that it can run its heater… and so on :-)

    Anyway pthomas745, I noticed that with the battery disconnect switch to “off” I can still login to the smart shunt on my phone, so I assume it’s still drawing power from the battery (unless it’s pulling directly from the panel?). From the wiring diagram on another forum post it looked like the solar controller fuse would also take the smart shunt out of the equation and truly disconnect the battery, so that’s why that was my first thought. Happy to be corrected though! 

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  • pthomas745pthomas745 Administrator, Moderator Posts: 4,347
    The battery heater, if it kicks on, uses 1.6 amps for each hour it is on. That would be "per battery".  The battery heater would only be a factor if: the battery actually requires charging.  Since most all of the lithium batteries have "low temp charging protection", the battery would not charge if the battery (the interior of the battery itself...not the outside air temperature) was below freezing, or close to it.  It would be just as simple to insulate the battery with a blanket, leave the battery switch and the solar fuses alone, and simply let the solar put back the very very low "self discharge" of the battery.  It might take a few weeks for the voltage to drop low enough for the solar to have to kick in to replace the small voltage loss over time.
    The "draw" of the Victron devices is very very small.  
    Don't take my word for it: you have some time before the entire NE becomes buried in snow!  Turn the battery switch off, and leave all the fuses in place.  Take a screen shot of your Victron status pages.  In the Smart Solar app, turn the "Charging off" on the battery settings page.  Watch the state of charge of the battery for a week or so with the Solar controller app and the Shunt app.  See how long it might for the battery to "self discharge" even 1 percent.  Test this for  yourself.  
    2017 Outback
    Towed by 2014 Touareg TDi
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  • benpcbenpc Member Posts: 6
    Ah okay! That’s super useful, and I will run that test. 

    So I think wthis means the only time I would ever use the battery heater switch would be dry camping in the winter; in other words, significant discharging AND charging in freezing conditions. It sounds like discharging the battery a little bit in the cold is no issue when it’s in storage, and when the temps rise the solar will top it back off. 
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  • pthomas745pthomas745 Administrator, Moderator Posts: 4,347
    The only thing in the "cold" scenario is if the inside of the battery (the actual battery cells...inside the battery) are below freezing...and  you try to charge that freezing battery.  Instant damage will result to a lithium battery when trying to charge it when the battery is below freezing.  (Fill in several caveats here....)  Mentioned above is the circuit in the battery called the "low temperature charging protection" circuit that prevents any charging when the battery is below freezing.  
    You can discharge a battery all you want under those conditions, and...the battery itself will "release" heat as the battery provides power.
    Think about where your battery is inside the 400, and try to imagine temperatures inside the trailer that are so cold that the areas under the bed are below freezing. 

    2017 Outback
    Towed by 2014 Touareg TDi
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  • BillCBBillCB Member Posts: 50
    FWIW last winter I simple disconnected the positive battery terminal and left a 25 watt bulb  (with an extension cord to my house) in the battery compartment. Everything worked fine in the spring as long as I followed the advice above re the order of reconnecting.
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