Garmin eTrex external charging

[zigzag]

etrex'es use aa, which is very convenient, but let's say i'd like to have a device running from an external power bank (to eliminate the faff of changing batteries). i've tried it with the screen backlight off and the unit draws so little power that the power bank "thinks" nothing is connected and switches itself off after half an hour (tecknet 9000mah). with the backlight on it carries on charging, but i'd rather save power and use backlight only at night. are there any tricks to keep garmin running from the powerbank with the backlight off?

[mcshroom]

How about setting the back light to come on for 30 seconds when you press the power button, and then do that every 20 mins or so?

[Kim]

This is why cache batteries that turn themselves off when there's no load are a work of Stan.  (See also the plug phone into battery and go to sleep use-case, where you wake up in the morning to find the battery has turned itself off after the phone finished charging, and it's been running on internal power for several hours.)

[thing1]

On occasion we've resorted to plugging both a phone and a garmin into a tecknet or Anker similar, as their combined trickle charge currents seems just enough to keep the lights on.
 

[PloddinPedro]

Zigzag, are you using the eTrex with the rolling map showing? If not, might that draw sufficient to keep the power pack alive?

[zigzag]

thanks for the replies. the ideal option would be plug in and forget for few days.

Zigzag, are you using the eTrex with the rolling map showing? If not, might that draw sufficient to keep the power pack alive?

yes, rolling map doesn't seem to draw enough power; only when the backlight is turned on (even if on lowest setting) the power bank keeps charging.

[frankly frankie]

The power drain is around 60-70 mA
with backlight
20% add 25ma, 30% 33ma, 50% 53ma, 100% 103ma

(from an ancient internet source)

so I would guess your power source needs about 100mA drain to keep running.

[zigzag]

i still keep on experimenting. two days in and the external battery is showing half the charge remaining. on a side note, gps clocked 40km in two days while sitting still

[Ningishzidda]

As an extension to your experiment.

Every three hours, or the equivalent of 50 km, toss a coin to make a random selection whether there is a 3 pin wall socket at the imaginary control.
If heads-up, disconnect the USB batt pack and put it on charge for 45 minutes.

Chances are that 45 mins will regain most of the spent charge.

This, of course, will require getting up from slumber at three hour intervals during the night. 

With friendly coin tosses, the experiment might go on for quite a time. 

[Ningishzidda]

Thinking further. Carrying the 3 pin charger for the USB batt pack, rest stops during rides of  600 km and longer will give opportunity to fully charge the USB batt pack.

Worry negated.

[zigzag]

if anyone's interested, etrex vista hcx with backlight on (the dimmest setting) was running for almost four days (93h43). if a typical day during long events is ~15hrs of riding, this arrangement would last for seven days.