Disregarding Murphy, the Mio will always be connected to external power, so
no low battery.

I hooked it up yesterday and spent a half hour or so sitting in the cockpit
making glider noises. Everything looks good. I appreciate the advice about
the 302 acting up and, should I see that sort of behavior, will simply
switch batteries or shut off the Mio and see if there's any change.

It's hard to imagine the Mio using much more than 300 mA.


"Martin Gregorie" wrote in message
...
On Wed, 02 Nov 2011 13:18:20 -0500, Paul Remde wrote:

I suspect that the iPAQ's battery was low. The hx4700 draws only about
300 to 400 mA when the battery is fully charged. But it can draw well
over 1 A when the battery is low. The 302 would probably work fine if
you connected the hx4700 to it when the battery was fully or nearly
fully charged.

I'd agree. I have an ancient iPAQ 3630 which specifies that its 5v
connection can draw up to 1.4 amps from a charger or whatever. As it is
supposed to run for 3 hours from a full charge and has an 800 mAh
battery, that implies that it uses around 270 mA during normal operation.

Its also worth remembering that the USB 2.0 spec says a connection should
be rated for 800 mA - and there are some devices that will try to draw
more than that. However, it would be wise to size the Mio power supply
for at least 1.5 amps[1] rather than 0.4 amps because at some point
Murphy guarantees you *will* connect the Mio with with an almost fully
discharged battery.

For what its worth, I bought a cheap 12v charging cable off eBay for my
iPAQ and took it apart. The cigar-lighter end contains a very small
12v - 5v converter rated at 1.5 amps. I installed it in a small metal
box (these small switch-mode voltage converters may stick out a lot of RF
hash) and permanently wired its 12v side to the glider battery. I have
lots of bad experiences with those cigar lighter plugs leaping out of the
socket for no apparent reason, so wasn't going to risk using one: besides
they are very bulky. The iPAQ is long retired, but I'm still using the
voltage adapter, which has to date powered the iPAQ 3630, a Garmin GPSII+
and, currently, my Binatone B.350 PNA.

[1] or the Mio's rated max input current, whichever is largest.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |