I think Sparra's point is still a valid reminder - particularly for those readers who may be looking here and may think that they can fully charge their battery in an hour and be set to go again. At best the alternator will charge a battery to 75% or so and we all need to remember that if we're depending on the power. If it's just for a few more hours then of course it'll be cool - but some readers might be wanting power for longer.
I'm not sure that the alternator can put out 60A at idle. The service manual's chart for the D40 alternator looks like this:
More than 33A @ 1,300rpm
More than 105A @ 2,500rpm
More than 122A @ 5,000rpm
That would imply that the output at idle (approx 750rpm, mine idles between 742-748rpm at the moment) would be much lower, so if you're depending on getting 60A from it, you might find it coming up short.
Still, even at idle, it is going to pump something out - so for anyone that wants to rely on their alternator to charge a battery, don't be too concerned if it takes a little longer for the battery to charge. It's a handy technique to use - so thanks for pointing it out!