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I don't use my car very often, and it often ends up sitting for around two weeks at a time. Over the past month, I only drove it about 5 blocks to repark it. Today when I reparked, it took considerably longer to find a parking space, so I'm confident the battery got fully charged, but it made me wonder if the battery would be at risk of getting drained if I had only driven a few blocks like last time.

Does anyone know how long the engine has to run to replace battery charge lost over a few weeks of sitting? Can I use the voltmeter on my ScanGauge to assess the state of charge and determine if I ever need to idle the engine to recharge the battery (as much as I would hate to do that)?

You could maybe look into a small solar panel to put on your dash/rear deck that can act as a trickle charger... otherwise, I would drive the car somewhere to charge it because the battery won't really charge at idle...it charges faster/more efficiently when the engine is around 1500-2000 rpm I believe... If your battery steady state is 12.4V or higher, I am guessing you should be alright.

Here is an inexpensive solar panel charger that plugs into the 12V port in your vehicle (only works if it remains HOT when key is off).

Wagan 2107 Solar Power Battery Charger (http://www.google.com/products/catalog?q=solar+panel+battery+charger&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&cid=6491180813522287951&ei=Q8dNTZL2DM-dgQflhpkL&sa=X&oi=product_catalog_result&ct=image&resnum=4&ved=0CEAQ8gIwAw#) .... I would call it more of a maintainer really...

Harbor Freight sells a small charger for about $8. and sometimes on sale for $4-$5 that you can plug in and leave it indefinetly. It will charge the battery when it gets low and automatically cuts itself off when no charge is needed. I've got a few of them that I use for lawn mower and motorcycle batteries during the winter. I've had them for about 3 years and they're still working. I'm not sure of the amp rating, but it's probably either .5 or 1 amp.

I had a battery go bad prematurely because I didn't use it for 4 months straight, and multiple times a couple of months non-use. I now charge the twice a month when it isn't being used. That seems to be sufficient, based on the amount of time before the "fully charged" light comes on. However, newer and fancier cars tend to have a lot higher parasitic loads. It sounds like running a power cord to the car could be a problem, so the small solar cell sounds like a great idea (wouldn't work so well in my garage!). I'm sure it could be direct-wired if the 12V port doesn't stay powered.