Kevin,

I'm probably jinxing myself by saying this, but oh well.

My battery is older than 4 years and it isn't unusual for my car to sit for 2-3 weeks at a time without being touched. Thus far I haven't had any issues with the battery and I've never used a trickle charger.

If you get a new, fully charged battery it should be fine sitting unattended for a week or two based on my experience. Of course there is a chance that you have an alternator issue or something draining the battery that is causing your problem.

Best of luck and enjoy the new garage.

Derek

On the subject of battery disconnection does doing so change the ignition key in any way? Just the radio codes to contend with and the lapse in DME acquisition of driving data, is that correct?

Yes, disconnecting the battery does not harm the car. Mine is disconnected 5-6 mos. every year for the past 10 yrs. with no ill effects. I remove it from the car and sit it on my bench on a tender (garage is semi-heated but above freezing and stays 35-40 degrees all winter). Spring startup takes the DME 1 drive cycle to re-adapt.

Replace the battery
 

Get a new battery ... from where ever, will cost you $100. When in doubt, change the battery. You own a Boxster, its probably the cheapest thing you'll put into the car.

I'd be more worried about
 

what was happening that drained the battery enough in 2 weeks that there wasn't enough juice to start the car.

It seems to me that there can be 3 things happening, either you put the car away with a battery that wasn't fully up to charge, the battery itself will not hold a charge or there is something in the car draining the battery.

I regularly don't use my car for 2 weeks at a time and it starts right up. And my battery is at least 4 years old. I only maintain the battery if I know I have (or will) not use the car for more than 2 weeks.

And if you have to replace the battery, there is no reason to spend $200 at the dealers when there are a dozen batteries just as good that fit perfectly. I don't go to the Honda dealer for a Honda labeled battery, I go to a discount store and buy a well regarded name brand battery. For a list of batteries known to work/fit in a Boxster, go here .

So lets deal with the "drain" causes one at a time:

1. Your driving right before you parked the car was such that there were multiple starts or you played the radio for 2 hours by washing it or something else that caused the battery to be already at low voltage when you parked it. It then further discharged.
2. The battery electrolyte had "burned" off so the battery wouldn't fully charge. You have a not fully sealed battery. And then the normal drain drained the rest of the juice.
3. You have something in the car like a broken switch that is keeping something on or an after-market GPS or cell phone adapter or radar detector or ?? that is on even when the car is parked and is draining the battery of its juice.

If #1, don't do that...in fact make sure you've driven the car 20 miles with the lights and a/c off just before you park it so it gets parked fully charged. If you think this is it, just jump the battery for at least 10 minutes with the donor car running at 3000RPM to get the battery back up to charge, don't start the Boxster, disconnect the battery now and prepare to reconnect and jump the battery in the spring.

If #2, then take the caps off and fill with distilled water to the mark or over the top of the plates. Then jump start the car after leaving the jumpers connected for about 10 minutes. Then drive it those 20 miles. If the temperatures or conditions don't allow that, then take the battery out of the front trunk and to an auto service place and have them test and charge the battery (make sure you have your radio code handy when you go to reinstall the battery if your model year requires a code).

if#3, then once the battery is fully changed, measure the voltage and come back a day later and measure again. And in a week. See a significant downward trend over a day or week and you have something draining more than a normal Boxster and are going to have to either solve the problem or maintainer the battery if you ever leave the car for more than a few days. You can either take the car to a mechanic and expect a big bill for the diagnosis or figure it out yourself by measuring the current draw and pulling fuses one at a time to see what circuit the draw is coming from.

One little thing I do to every battery I put in a car is write (use a Sharpie) on the top of the battery when you installed the battery. I could dig throught files to find the receipt / date, but this is quick. We've done this on boats for years.. rather handy when you talking about multiple batteries and you have no idea which is older/newer.