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Brightness when plugged in?

I use my Nuvi on my Harley and have it set on 100% brightness in order to see it at all. When the battery dies and I plug it in, the brightness suddenly is reduced and I cannot see it in the sunlight. Can I override this function or am I reduced to plugging it in periodically and then unplug it in order to see it? Any help is greatly appreciated. Thanks


  • Boyd 1985 Points
    What model nuvi do you have, and how are you powering it? That makes a big difference.

    If you have a model that originally used a powered cradle (the 6x0, 7x0, 7x5, 8x0 or 8x5 series), then you MUST use the cradle if you want the screen to run at full brightness. You can plug these into a generic USB power cord and they will work, but the brightness will not reach full even though you set it for 100%. This is a known issue, and Garmin claims that it's intentional (why??).

    Other models which were designed to be powered directly with a USB cable don't have this issue. These would include the 2x0, 2x5, 12x0, 13x0, 14x0 and 37x0 series.
  • I have a 765T and you are correct, the USB cable is how I am powering it because the cradle cord is quite bulking for the motorcycle. I guess I will have to use the big cord if I want to see it. Thanks for the help..
  • wfooshee 91 Points
    Full brightness too much current for USB???? They know their power supply can handle it, but full brightness may be over generic USB specs for current.
  • Boyd 1985 Points
    I have heard people suggest that before, but I don't buy itl. If that is the case, how come models like the 255w, 1390, 1490 and 3790 can run at full brightness with a USB power supply? These screens are comparable, and in the case of the 3790, far brighter than any other Nuvi while the 1490 has a 5" widescreen.

    It appears to be an intentional thing from Garmin, but I don't understand the logic. Why should units that use an active cradle be any different? The 3790 has an active cradle, but the power input is a standard USB mini plug. I have used mine with a 3rd party power supply and it worked fine.
  • It isn't where the power goes into the unit, it's where it comes from. They can use the USB plug on their unit and pump 80 amps through it from their own supply if they built it right. They certainly couldn't draw that from a generic USB cable from a PC.

    None of us knows what's inside the thing drawing power, except by the rating on the label, so comparing blindly to other units means nothing. I still think that it's a measure to protect the USB power source from excessive draw. That's a logical and sensible reason for it to work that way.
  • SergZak 340 Points
    It appears to be an intentional thing from Garmin, but I don't understand the logic. Why should units that use an active cradle be any different?
    I agree with Boyd. Using the exact same power supply (12v standard Garmin car adapter) plugged into the USB mini-B port , the cradle-based nuvis (7x0/7x5/8x0/8x5) all run at reduced brightness compared to non cradle-based nuvis.

    I can understand the reduced brightness being a factor if using a PC's USB port due to the limited current to the USB ports but the non cradle-based nuvis are fully capable of detecting the 12v standard Garmin car adapter and running at full brightness. You would think that the same would be true for the cradle-based nuvis when they're connected to the same power supply plugged into the USB port (rather than the cradle) but they apparently are not and refuse to run at full brightness when powered in this way.
  • Boyd 1985 Points
    Using the exact same power supply (12v standard Garmin car adapter) plugged into the USB mini-B port , the cradle-based nuvis (7x0/7x5/8x0/8x5) all run at reduced brightness compared to non cradle-based nuvis.
    That was exactly my point. I was talking about using THE SAME USB power supply on both units. The unit with the cradle will be dimmer. This has nothing to do with current coming from the USB port. I have tried this with genuine Garmin as well as third party USB cigarette lighter power cords and the result is the same.

    BTW, Garmin has further confused the term "cradle-based" now because the active cradle on the 3700 series uses a standard min-USB cable as well. And as an interesting aside on that topic, the 3700 knows when it's in the cradle, even if power is not being supplied.

    If the 3700 is "asleep" when you wake it up OUTSIDE of the cradle, it requires you to tap a screen button twice to unlock it. If you wake up a sleeping 3700 INSIDE the cradle but with NO EXTERNAL POWER, it does not require you to tap the unlock button.
  • I understand where you guys are coming from, but my point is that if the unit isn't cradled, it makes the assumption that it's not powered by the Garmin supply (which may be stronger than the USB standard) so it reduces maximum consumption to comply with USB standard. The limitation is not the port on the GPS, it's the external device which is supplying the power. A USB port on a PC can only supply x milliamps by standard, and the Garmin supply may be able to do more than that.

    It's not detecting the supply, it's detecting the cradle, or lack of. It can't tell one USB plug from another and then "know" that it's OK to draw more current. It simply makes the assumption that if the cradle is off, then it may be powered by a connection not capable of supplying enough current for full brightness, and limits the brightness to protect the device supplying power.

    If it's in the cradle, it "knows" that it's being powered by a Garmin supply, and allows full brightness.

    Even with Garmin's adapter in the USB port, without the cradle it simply doesn't know where its power is coming from, so it limits its draw, even if it's using the same plug to get the power.
  • SergZak 340 Points
    The cradled nuvis are fully capable of detecting current coming from whatever is being used to supply the power...a USB port on the PC, a Garmin 12v power supply, a Garmin AC power also detects the current coming from the cradle mount. This can clearly be seen in the nuvi diagnostics.

    The non-cradled nuvis also have this ability to detect current.

    The point is that the non-cradled nuvis will run at full brightness, regardless of what is being used to power it via USB while the cradled nuvis will not...which seems pretty silly to me considering that both can detect available current.

    BTW, I see where you're coming from as well.
  • Detecting current does not mean they know how much is available. No device can measure the current capacity of its power supply. If the device uses more milliamps than the supply is rated for, bad things happen to the supply.

    The USB standard is 500mA. The GPS receiver is going to need more than that for full brightness. Without the cradle it limits itself to 500mA to protect what may be (it has no way of knowing, remember) a limited USB power source. With the cradle it knows it has its own higher-capacity power supply (the cradle uses the Garmin-supplied power adapter) and allows full brightness. It really is that simple.

    I think you'll find that the non-cradle units will have a lower power consumption rating, assuming you can even find the spec listed anywhere. (Thus the requirement for having the cradle in the first place.)
  • Boyd 1985 Points
    Methinks you are arguing just for the sake of argument. :)

    It's just (at best) a misguided design choice to limit brightness when not in a cradle. Models with identical (1350) and even larger screens (1450) can maintain full brightness when using the exact same power adaptor. Do you really think the 1490t draws less power than a 755?
  • Don't have any idea how much it draws. Neither do you. :D (Meant in fun, not a personal dig!!!)

    There's lots more stuff in there besides the screen, so screen size alone is no indication of current draw. Measuring it with an ammeter is the only real way to tell. Maybe one device has a more efficient radio receiver than another. That would lower its power requirement.

    I see why folks would wonder why this would happen, but limiting current draw by limiting brightness is a logical process to use when the power supply is an unknown source.
  • Boyd 1985 Points
    Garmin should hire you to coach their customer support reps in what to say when people call to complain about how dim their 755 is on their motorcycle. :lol:
  • Hey, I've said WAY more than I've ever heard from any of them . . . . :lol:
  • Boyd 1985 Points
    Basically all they need to tell the complaining customers is, "it's not a bug, it's a feature". :lol:
  • Thot 0 Points
    Hello Guys,
    I just got a used Garmin Nuvi 680, went through all the trouble to add a 12V outlet to my motorcycle, only to discover the problem discussed here.
    When plugged, the brightness is at 30% (regardless of what the brightness slider says), way too dim to see it when I ride on daytime!
    I tried other power sources (my car, for instance) with the same result.
    My guess of why this is (to protect the source or a bug that Garmin turned into a "feature") is as good as anybody else's.

    My question for those who know more about it:
    Does anybody have come up with a hack to fix the problem?
    Is there any way to make the unit "think" it's connected to a cradle even if it is just connected through the mini USB (and a 12V car adapter)?
    It may be as simple as shortening some pins on the cradle connector, but which ones?

    I don't have a cradle, but even if I did I could not mount it on my motorcycle, too bulky.

    Any help would be appreciated
  • ozarkie 84 Points
    Basically all they need to tell the complaining customers is, "it's not a bug, it's a feature". :lol:
    :lol: :lol: :lol:

    (I hope Microsoft isn't reading this forum...)
  • Billw439 0 Points
    My thoughts are it is dimmed just to extend battery life. If in the cradle it is being powered. If not it is considered on battery. Just like my laptop. If set for energy saving the display is dimmed.
  • Thot 0 Points
    It's actually the other way around.
    When it is UNPLUGGED (and relying entirely on battery) the brightness can go to 100%.
    When you plug in directly (without the cradle) you are stuck to 30%.

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