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Cubby USB not working on battery (Tab 400)

TomCanadaTomCanada Member Posts: 290
edited April 2021 in Battery/Electrical & Solar
I just learned that the USB receptacles in the bed cubby do not work unless the inverter is on.  I'd like to charge my phone here overnight but I don't want to run the inverter while boondocking since it's such a power hog.  Has anyone rewired the USB part of this outlet to run straight off the battery rather than via the inverter (or installed an extra battery-powered USB here?).  I'm confused why this would be wired up via the inverter - there doesn't seem to be a logical reason for it..

Edit: seems that the combo AC/USB outlet itself takes 120V from the inverter (or shore power) as its input - I'd need to wire up a separate USB receptacle, probably tapping into the 12V coming into the light switch in the cubby. Which brings up the next question - anyone know how to remove that switch? :)
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Comments

  • Michigan_MikeMichigan_Mike Member Posts: 2,861
    Tom,  

    You state that your bedside cubby USB receptacles do not work unless the inverter is on.  Are you really referring to the electric converter on the trailer, the dark colored box that contains the trailer fuses?   I’m guessing you found this out (the USB port wasn’t working) while the trailer was on shore power too.  Make sure the battery shutoff switch is on too so the trailer is powered up.  The USB ports run off the battery and if you do have an inverter (that provides 110 volts) that wouldn’t provide power to the USB ports anyway.  Hopefully things get restored but I’m guessing your trailer “on/off” switch at the battery is in the off position.  
    Mike - Elmira, Mi / 2019 T@B 400 / 2021 Chevy Silverado LTZ
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  • pthomas745pthomas745 Moderator Posts: 3,989
    Does the "power hogging" inverter overwhelm the convenience of using the plug?  The inverter would use some power, of course.....but not nearly as much as the "thing" you might be charging.  If you have a big battery, installed solar, and a phone that might take an hour to charge, why go through all the gyrations to rewire the outlet.  (I realize that charging "all night" would then just be running the inverter needlessly).
    2017 Outback
    Towed by 2014 Touareg TDi
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  • TomCanadaTomCanada Member Posts: 290
    @Michigan_Mike the USB port works fine on shore power - after some digging I learned that the combo 120v/USB receptacle in the bedside cubby runs off a single 120V input and then internally generates the USB 5V for those plugs.  This particular socket is powered off the inverter, and the inverter passes through shore power if present as well (even with inverter 'off').  However, without either shore power or an 'on' inverter, it turns out these USB's have no source voltage, and therefore are unusable.  A shame, but that's how it is.  I found another RV forum where people were looking for a combo 120V/12V input receptacle for a similar reason and read that apparently it's against electrical codes to run both a 120V AC and a 12V(or 5V) DC source to the same receptacle. The prevailing suggestion seems to be to install a dedicated 12V outlet off the battery and use a USB dongle (like what you'd use in your car).  I think that's my plan..

    @pthomas745 my phone has a honkin' battery and can take 3-4 hours at standard USB currents to charge (faster if using a fast charger, but again that requires either 120V+adapter or a 12V+adapter). The BMV tells me the phone sucks 0.5A when charging while the inverter itself is using 1.2A even when idle (1.7V if charging the phone).  That long charge time is why I like to leave it charging overnight - but if I do that I'll use a good 10Ah due to the inverter inefficiencies!  That's tough to swallow when boondocking for an extended period.  I get why the inverter outlet is where it is (CPAP machines), but I personally would find more utility in a 12V socket in that area, which I'll probably install at some point.  I also wish the inverter powered the kitchen counter outlet, so I might reroute that outlet from the converter to the inverter instead. But it's GFCI so I'm not sure what ramifications there are there (haven't researched that yet)

    Thanks for the responses guys!
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  • Michigan_MikeMichigan_Mike Member Posts: 2,861
    edited April 2021
    Sounds like you have things figured out and under control.  It just sounded peculiar is all, but once you start backtracking on these circuits things do make more sense.  I had heard that nuCamp had started wiring the inverters to the other 110V receptacles but in my 2019 400 there is only the one dedicated 110V receptacle.  I’ve never used, nor needed the inverter as it consumes considerable energy and it depletes the battery.  And I agree, the12V cigarette style outlet is a better choice in the corner for CPAP users as it’s much more efficient for a CPAP machine than an inverter.  
    Mike - Elmira, Mi / 2019 T@B 400 / 2021 Chevy Silverado LTZ
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  • pthomas745pthomas745 Moderator Posts: 3,989
    @TomCanada I didn't entirely catch the "all night" part.  So, yes, no matter how much nicer the batteries are these days..that would be a waste.  The good news is you have a large inverter.  The bad news is the inverter is too large for small jobs!  There are no other 12V ports in the 400?
    2017 Outback
    Towed by 2014 Touareg TDi
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  • TomCanadaTomCanada Member Posts: 290
    There are, but I get too lazy to go plug them in, and in the morning I like to use my phone to check the time.  First world problems!
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  • Denny16Denny16 Member Posts: 5,431
    Yes, there is a regular 12VDC auto style port in the Galley on the left side Wharton wall between the door and the sink area (backside of the main light switch and tank monitors).  There is also a battery powered USB (at least on the 2018/2019 models) up in the dinette under the table.  On newer TaB400s this has been moved to under the pax side dinette seat. Not sure this one is battery powered?  But on the 2018/19 models, thenUSPminmteh dinette works off the battery.

    It is easy to add RV style,12VDC/USB outlets, you just need a 12VDC source pulled to the area you want the outlet.  
    Cheers
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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  • TomCanadaTomCanada Member Posts: 290
    Fyi the pax side dinette on the 2021 400 has two receptacles:

    - combo 120V/USB - shore power only
    - combo 12V/USB - battery

    The other receptacles are:

    - Kitchen counter, microwave 120V: shore power only
    - Cubby: combo 120V/USB - shore power or inverter only
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  • berggerbergger Moderator Posts: 1,078
    If I need to charge overnight I just turn the phone off and use the 12v usb by the dinette.  Gets me away from the phone anyway while camping.  If you simply can't get away from your phone easiest way is to get very long cable and still use the dinette usb.  
    2021 T@b 400 BD  "Vixen Gail" 
    2018 Nissan Titan Pro 4X "Big Bird"
    Leadville Colorado
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  • Denny16Denny16 Member Posts: 5,431
    A long ext USB cord would be a trip hazard and will have voltage drop.  Not a great idea.
    cheers
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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  • NorCalMikeNorCalMike Member Posts: 52
    Since you guys seem like the electrical experts, does the inverter only drive the 110v plug in the cubby on 21 model 400?  Seems odd they don't have one in kitchen area if you want to run a coffee maker or small blender?
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  • Denny16Denny16 Member Posts: 5,431
    edited April 2021
    On the 2018/2019 TaB400 models, the Inverter only powered a receptacle by the galley, at the foot of the bed, which could be used by a coffee maker setup.  In 2020 they moved it and added an outlet in the dine area also.  Seems there are two variations with the 2021 TaB400, one which was similar to 2020, and one with only the bunk cubby AC power receptacle connected.  Some have an auto transfer wired with the trailer shore power, so the AC inverter outlets also work with shore power.  The AIMS inverter can be wired up in several ways, and it has two AC outlets on it

    That said, the inverter is only 1200 watts, giving around 800-900 useable watts, and eats battery power when in standby, and more when a AC load is applied.  It is too small to run a small microwave, and too large to use for a small appliance using 300-600 watts.

     So it really has limited use for short period applications whilst camping off grid.  For a small AC appliance, you are better off getting a small portable inverter that is matched to the small galley appliance you want to use.  Normal load on an inverter is 80% of its max normal watt rating.  There is a 12VDC power point in the galley you can plug a small inverter into, then plug your coffee maker into the small inverter.
    cheers
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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  • berggerbergger Moderator Posts: 1,078
    Denny16 said:
    A long ext USB cord would be a trip hazard and will have voltage drop.  Not a great idea.
    cheers
    I can't see a human tripping over a usb cord and it being an issue.  It would pull out of the socket before you cell down. Also just tuck it out of the way like any cord. And who cares about a negligible voltage drop on a long cell cable charging a cell phone over night. It will be 100%  in the morning when you wake up.  It's a simple, cheap option if you need you cell phone next to you and don't want to use the inverter. I like to not over think and complicate things. K.I.S.S principal. 
    2021 T@b 400 BD  "Vixen Gail" 
    2018 Nissan Titan Pro 4X "Big Bird"
    Leadville Colorado
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  • Denny16Denny16 Member Posts: 5,431
    Glad you are so stable Berger, but I have tripped on small cables like a USB or Eathernet cables.  
    Cheers
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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