External vs internal Battery Geko 201

I use my Geko 201 essentially to record tracks . I may trek for
several weeks without access to a wall socket, car power or battery
supplies. The internal AAAs tend to burn out quickly: one day is OK
but will fade out in the middle of the second day: so good for a day
only, imagine the number of AAAs to carry!. So I have fitted a combo
of two external D batteries to my Geko 201 and they are good for 8
days or more. However, I find that the internal batteries are still
depleted, they run longer than before but still do burn. How so?

1 Are they just busy checking that the external batteries still supply
enough power, or do they still supply power to part of the device
(screen, memory, controller, ...)

2 The signal "weak battery" comes out. When there is an external
supply does this mean in priority that the msg concerns the external
supply or only the internal battery or what?

3 I contemplate inserting directly the external battery supply through
the backcover to the plates where the AAA connect. Any advice to the
contrary? I know I will lose waterproofing but this is not an issue
here, and I am way beyond the garantee period.

4 I suspect the LCD screen is the largest power user in the device and
I do not need to watch the screen all the time, just when starting and
turning off. Is there an easy access to the cables driving the screen
and would it be too daring to cut this off and reconnect through a
switch (external naturally) so as to minimize drain.

5 Finally I have fitted a 12V battery (2*6V) with carplug to supply
power and that lasts all I need, but this is a bit heavy to carry and
it does not prevent the AAA to run out. However, it will recharge any
battery that needs it (e.g.camera). Any source for light weight 12V
battery?

Thanks,

Pierre

PierreL wrote:

I doubt that it's anything that sophisticated. Probably the internal
and external power sources are providing power in parallel with the
relative voltages having some influence on which provides more
current.
On my older GPS12 with 4 AA cells (nom. 6 VDC), the external power
input spec. was for anywhere from 6 - 8 VDC but I found that supplying
6VDC still had the internal batteries running down whereas they stayed
charged much longer with external power of almost 8 VDC.


Sounds ok to me with the caveats you already mention.

Seems like a rather risky procedure and I doubt that you'd get a
dramatic gain in battery life. I notice that my Garmins run much
longer when in demo mode with the radio receiver circuits turned off
than they do in nomal operation. So I think these circuits (and
associated processing) consume almost half of the power used by the
device. It'd be nice if Garmin provided a 'super-battery-saver' mode
of operation where the unit would only wake up momentarily every
minute or so just to get a quick position fix. That would frequently
be good enough for a decent tracklog and would greatly extend battery
life.

Hi, Pierre

:I use my Geko 201 essentially to record tracks . I may trek for
: several weeks without access to a wall socket, car power or battery
: supplies. The internal AAAs tend to burn out quickly: one day is OK
: but will fade out in the middle of the second day: so good for a day
: only, imagine the number of AAAs to carry!. So I have fitted a combo
: of two external D batteries to my Geko 201 and they are good for 8
: days or more. However, I find that the internal batteries are still
: depleted, they run longer than before but still do burn. How so?

The two batteries you are using as an external power supply will loose their
voltage as they get used and they are on the edge of what is needed for an
external supply.
Whilst the internal batteries can have a voltage as low as about 2.1 V before
the unit switches off, the externals must have a voltage of about 2.8 V at
least otherwise the internals will take over.
Amongs other things, battery voltage is depending upon temperature.
So once they get low, there will be times the internal batteries will take
over for some time.
Then, when the voltage of the aux batteries rises, *they* will take over
again.
Better option here would be to use a power pack that has a higher voltage, for
example 6V and use a low drop voltage regulator to bring the voltage back to
3.3 as defined for your Geko 201.
Disadvantage is that you will lose some current due to the conversion.
Latest option is to use an integrated circuit that is a switching regulator.
Effeciency is about 95%, but they are not yet widely available. (R783.3 ?)

:
: 1 Are they just busy checking that the external batteries still supply
: enough power, or do they still supply power to part of the device
: (screen, memory, controller, ...)
:
Nope, See above

: 2 The signal "weak battery" comes out. When there is an external
: supply does this mean in priority that the msg concerns the external
: supply or only the internal battery or what?

Just the internal. The only way you can see the externals are providing
current is that there is a little square drawn around the battery-indicator on
the screen ( the four small blocks left bottom)
This line is not present when there is no (sufficient) external power.

:
: 3 I contemplate inserting directly the external battery supply through
: the backcover to the plates where the AAA connect. Any advice to the
: contrary? I know I will lose waterproofing but this is not an issue
: here, and I am way beyond the garantee period.

No objection at all. However the way it is now is that you have a "spare"
power supply that takes over automatically when the external power supply is
depleted.

Regarding the waterproofing: If you would drill a little hole in the cover,
put the leads through and seal it again with some glue or whatever, your
problem would be solved.
:
: 4 I suspect the LCD screen is the largest power user in the device and
: I do not need to watch the screen all the time, just when starting and
: turning off. Is there an easy access to the cables driving the screen
: and would it be too daring to cut this off and reconnect through a
: switch (external naturally) so as to minimize drain.

Never opened a unit but I bet the display is 'glued' to the printed board
circuit or connected by a 'plastic' connector with very fine copper leads on
it. No way you can fiddle with that.

:
: 5 Finally I have fitted a 12V battery (2*6V) with carplug to supply
: power and that lasts all I need, but this is a bit heavy to carry and
: it does not prevent the AAA to run out. However, it will recharge any
: battery that needs it (e.g.camera). Any source for light weight 12V
: battery?
:
no no lightweigt but you can think about buying a small solar charger, capable
of charging AA and/or AAA nicads or Li-ions. Put it on top of your backpack
and you can recharge them while walking.
---It's my understanding you're walking otherwise you would have a option to
recharge your batteries from you vehicle's power source ever if it is a
push-bike (bicycle).

: Thanks,
:
: Pierre
:

Regards, Pocileh