Garmin Oregon and external power

[Whitestone]

I've had a quick search of these forums (and elsewhere) but can't find a definitive answer.

I've an Oregon 600. Currently I use a set of Duracell rechargeables along with a couple of bits of beer can to press the nipple down and fool the unit into thinking it's got the Garmin powerpack.

With that setup how does the Oregon handle an external power supply, i.e. a typical powerbank type battery? Does it run directly from the external supply or recharge the internal batteries and then use power from those? Does the unit handle internal rechargeables different from non-rechargeables so if I removed the bits of beer can then power would go directly to the unit?

I'm doing a long trip, circa two weeks, I have a dynamo hub and I'm intending to have two powerbanks, charge one and use the other to charge devices. There are two ways of doing this (as far as I can tell), both have pros and cons:
1. At night plug in the powerbank and let it recharge the internal batteries.
2. Run the unit directly from the powerbank not being charged. I've an "up angle" USB cable so it can be used whilst the unit is in the bike mount - hopefully not stressing the board connector.

Obviously I can try myself but typically I've only thought of this at the last minute as we are heading off tomorrow

[Ham]

I would not use oregon internal recharge - it doesn't seem to work very well.

[Whitestone]

OK. Some observations.

When you run the Oregon from an external power supply it ignores the power saving settings So the screen is on all the time, consequently you use a lot of power, certainly more than I could recharge via the dynamo in the same time. Garmin must assume that an external power source has infinite capacity.

External power seems to both charge the batteries as well as running the unit. This then exposed another problem: the Oregon drained the external battery at which point it determined that the external power source had been removed so displayed the "External power source removed - turn off/stay on?" screen. Of course this happened when I wasn't on the bike so the unit turned itself off!

My wife has the Oregon 700 and this has the same problems.

This is something that is relatively easy to fix by Garmin, there needs to be menu options to set the type of external power supply - battery/AC/vehicle or similar and to be able to disable the "power lost" screen or at least default it to staying on. The power saving options should be used if external battery is selected.

[Kim]

Garmin must assume that an external power source has infinite capacity.

They've probably only considered that it would be used with a vehicle supply.

[Ham]

Can I point out that the backlight is very easily switched on and off? (power button/swipe if you haven't reconfigured the button) but I'm not sure that was the entire cause of your woes, that without it your dynamo would have provided power for a significantly longer.

[Whitestone]

@Kim - that's sort of what I meant - lighter socket to USB. Then again they don't sell the Etrex/Dakota/Oregon/Montana models as biking units, there's the Edge series for that.

@Ham - It's still different behaviour from when running from internal power, why override user settings? I know that when using the internal batteries then a quick press of the power button brings the screen on/turns it off. Didn't realise (or indeed try) to do so when I was running the unit from external power. I'll have a play tonight.