Seems like a lot of work and hassle when you can buy a battery charger for
$20 to $50.
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it could be but for those of us that like to keep stuff out of the waste
stream and have ready access to boxes of power supplies it start sound
like fun. :)  then again it seems like with these instructions you could
pop one out every 15 minute and say do 10 if you had the power supplies
and stuff ready.  then you would be set for a while and perhaps some of
your friends might be as well.  it all about the economies of scale.

$20 * 10 = $200

10 * 15min = 150min  => 150 min / 60 min = 2.5 hours

$200 / 2.5 hours = $95 per hour

sounds like a fun rainy day project to me :).  at a good way to justify me
hoarding all those power supplies.

jonathan