On Sat, 17 May 2014 16:15:53 +0100, TonyL
wrote:

On 14/05/2014 16:54, Johny B Good wrote:
Pure use. But credit where it's due . . .
It still seems a 'half assed' fix to me. All they've done is used a
larger case to accommodate a much bigger battery compartment rather
than use a technique of reducing power consumption similar to that
which was used to create small MP3 players that could run for 6 hours
off a single AAA alkaline cell.


And some more. I'm painting some railings today with a Sony MP3 player
for musical entertainment. This player behaves and looks like a USB
memory stick and is also charged via USB. I've been out there for some 6
hours and there is still about 70% charge in it (according to the
display). Haven't a clue what cells are used. I do know that they can be
fully charged from a PC USB socket in less than 60 mins.

Most likely a LiPO cell (3.7v or so - just like a mobile phone
'battery' except far smaller). At that voltage, it can probably
directly power the cmos logic directly with no danger of 'reverse
charge' (probably just needs a low voltage cut out added to the switch
on/off logic to avoid 'bricking' the 'battery'.

At that voltage, you'd only need half the AH capacity of an alkaline
AAA cell to get a 6 hour endurance assuming a similar power
consumption by the logic and headphone amp. AA alkaline cells have
1.2AH nominal capacity so a 600mA LiPo would do the job.

If you can recharge a 3.7v LiPo from the usb port in just one hour,
that implies a 500mA capacity. The extra endurance suggests yet even
greater improvement in battery consumption than the earlier "6 hours
on a single AAA cell" example.

Here's a link to a wiki article:

http://en.wikipedia.org/wiki/Lithium_polymer_battery#Personal_electronics


--
Regards, J B Good