eTrex Vista 'randomly' switching itself off - suggestions?

[Greenbank]

Another method is to solder a capacitor across the terminals in the battery compartment, that way if the batteries are rattled and stop providing power the capacitor has enough charge to prevent it turning off.

Can't find the page with the best instructions but googling for "Garmin battery capacitor" gives some examples...

[hazeii]

To add to that, if the capacitor is soldered into the battery compartment it only helps if the issue is loose batteries (doesn't fix the PCB contact problem) - it needs to be soldered inside the unit for best effect. Even then, offroad it isn't 100% - the full-spectrum approach works for me though (stretch battery clips,fit  capacitor, use external batteries).

[Greenbank]

FWIW I haven't had a single unwanted power-off since I've used a zip-tie to lash it more securely.

[Sergeant Pluck]

That's interesting. Prior to the weekend I had the HCx mounted on an Acor bar extender tightly mounted to the bar. The bracket was an oversize one padded out to fit on the normal size Acor. So a little bit of give, but not much. Never switched itself off due to road shock despite some hard hits.

Prior to Saturday's Swindon ride I thought I'd fix somthing that wasn't broke, and refitted the Acor with a couple of strips of rubber at the bar clamp. So there was a bit of give there and some movement when going over bumps, which I hoped would have a shock absorbing effect.

Not so. For the first time, on Saturday, it switched itself off 3 times, twice over cattle grids at a fair speed. Over bumpy sections the device appearred to be vibrating quite a lot.

It seems it is better, unless you have some way of damping the vibration, that a more solid mounting is better, which ties in with your experience.

I shall update in due course.

[The Mechanic]

I have a Vista HCX and have never had this problem.  I have come across another issue to do with Lithium batteries.  I have been using them because they give much longer run time than the duracels I was using.  However, I have discovered that, when the low battery warning comes on on the Garmin, you have about 10 seconds before the unit shuts down.  With duracels this can be several hours.  This must be a feature of the lithiums.  I guess that they have a very flat power curve that frops like a stone at the end.  Bit of a bummer when you are half way up the Cabrach and don't want to stop for fear of not getting started again.

[Sergeant Pluck]

Is the battery type set correctly?

[The Mechanic]

Errr... No!  It is still set to Alkaline.  I read somewhere that this was a good idea as it made the batteries last even longer.  I will check out the instructions.

[frankly frankie]

If you're using Energizer Lithiums then 'alkaline' is the best setting, IMO. 
I have seen them give up to 50 hours (in a Legend Cx) but it is true that you don't get much time after the 'low' warning - 5-10 minutes at most.  Carry a spare pair - they don't weigh much after all.

Regarding the vibration problem - it does seem unclear whether the best fix is a more compliant mounting (oversize mount with layers of rubber), or a more rigid mounting (eg http://www.gpsw.co.uk/details/prod2394.html ) - both have been tried with some success.  I prefer a compliant mount but I think eliminating the 'rattle' using layers of PVC tape as described earlier, has helped a lot too. 
Just completed a week of touring on very rough roads where three of us all using the simple anti-rattle PVC tape didn't have a single power-down between us.

[JJ]

FWIW, my Legend Cx was doing this off periodically ever since PBP.  The other week it suddenly got really bad.  Now sorted by replacing the clip on the back plate which had a hairline fracture, and putting duct tape on the handlebar bracket.

Lithium batteries last for ages PROVIDED you don't inadvertently leave the backlight on all day.  If you tend to do that, I recommend a cheaper option!

[Sergeant Pluck]

Regarding the vibration problem - it does seem unclear whether the best fix is a more compliant mounting (oversize mount with layers of rubber), or a more rigid mounting

The only time I had this problem was when I tried a more compliant mount. If the shock-absorbing motion cannot be effectively damped then it is better to have a firmer mount. IME.

[Dave]

Regarding the vibration problem - it does seem unclear whether the best fix is a more compliant mounting (oversize mount with layers of rubber), or a more rigid mounting

The only time I had this problem was when I tried a more compliant mount. If the shock-absorbing motion cannot be effectively damped then it is better to have a firmer mount. IME.

Using the Vista on my MTB and Moulton, both of which have some sort full suspension causes the unit no problems at all. It's only on my Roubaix that it happens. IME, a more compliant mount and lighter batteries has significantly reduced the problem on the Spesh (cattle grids are still an Achilles heel, as Pluck knows ).

It definitely seems to be particular combinations of amplitude and frequency that cause the problem.