left lights on, killed batt. Charge or replace?
 

Newb mistake, left head lights on in garage, batt fully dead. :(

Do I try to resurrect by charging (need to buy charger), or replace
battery and move on? I've had success charging other vehicles in the past,
but I have zero mechanic type knowledge.

If replace, what is a good one for 2002 Boxster?

I did that to mine just bought a ctek battery maintainer and charged it up again. How old is your battery?

I don't know about the ctek or other trickle charger, but here is my story...

I've had batteries completely drain on more than one occasion. So drained that when I connected my battery charger... it refused to charge because the battery was spent. So...

I would remove the battery... hook up another battery.. start the car... remove that battery (with the car running)... hook up the dead battery... and let it "charge" for about 15 minutes. I'd then shut off the car... hook up the battery charger... and the battery would register just enough juice to allow the charger to do the job. Has worked every single time I've encountered that problem.

You don't have a charger... so after you reinstall your dead battery... go for a long drive. That'll get you back to normal.

Good luck.

If your battery is more than 3 years old, it probably won't live thru another mid-west winter.
If you charge it slowly, it shouldn't have ruined the battery, Charge it too fast (as in jumping) and you could warp the plates and ruin the battery.

I would not feel comfortable disconnecting the battery while the engine running as you may damage their sensitive electronic systems and may be more expensive than a new battery..

I had a dead battery a year ago after leaving the lights on. It was only 2 years old at the time. I connected my Schumacher maintainer and it charged after a few hours. Fired right up and I haven't had an issue since. BTW, if I'm not going to drive for a few days, I connect the maintainer. And of course it is always connected when the car hibernates over the winter.

thanks, all, MUCH appreciate the advice. I found a decent slow charger to borrow, so I might as well give that a shot.

Unsure how old it is - bought car used - so I shall check on that as well, and replace if needed. :)

There should be a sticker on your battery that shows when the battery was manufacturer. It can say the month and year (April 2014) or some will have digit code like tires (example: 4018) which means it was manufactured during 40th week of 2018. If your battery is more than 5 years old, it might be time to replace it after this incident.

Ditto, that doesn't sound like a very good idea. Maybe try hooking the batteries up in parallel?

When the car is running... it's all alternator. When the car is running there is a slight charge delivered to the battery (preparing it for the next "start"). Remove the battery when the car is running and... voila. Car keeps running (assuming a properly functioning alternator).

What? A Porsche is the only car with sensative electronics? I've done it on my Edge, and the electronics on it are FAR more sensitive than a 98 Porsche.

Has worked for me since, um, the 70's.

Cheers!

I wouldn't do it. Think of the battery as a capacitor that absorbs electrical spikes, if there are any. Absent the battery you run the rick of frying something. Not that it will necessarily happen, but the risk is there. It's a foolish risk, IMO, with no reward.

From:

https://mechanics.stackexchange.com/questions/38926/what-happens-if-i-disconnect-the-battery-while-the-car-is-running

"Your battery does more than just provide electricity. It also shorts AC spikes and transients to ground. Removing the battery from the circuit allows those spikes and transients to travel around, endangering every semiconductor circuit in your car. The ECU, the speed sensitive steering, the memory seat adjustments, the cruise control, and even the car's stereo.

Even if your computers and stereo remain intact, in a great many cases removing the battery burns out the diodes in the alternator, necessitating a new alternator. If disconnecting the battery interferes with the voltage regulator's control voltage input, it's possible for the alternator voltage to go way over the top (I've heard some say hundreds of volts), frying everything.

Even the initial premise was wrong. If you disconnect the battery and the car conks out, you don't know if it conked out due to insufficient alternator current, or whether the resulting transients caused your ECU (the car's computer, which controls fuel mixture, timing, and much more) to spit out bad data, shutting down the car.

Nobody should EVER run your engine without a battery.

And yet when you tell them not to, they'll roll their eyes. "I'm a professional. I do this every day. It's fine!" They'll sound so authoritative. So commanding. So in charge. So intimidating. But they're wrong.

The problem, of course, is that disconnecting the battery doesn't always damage something. It does it only sometimes. Less experienced jump start professionals and automotive technicians figure if they got away with it a few times, it must be OK."

Why not jump start it? Hook it up to another car's battery (donor car not running) let it sit a few minutes, then start the donor car, then you car.

ha! Why didn't I even think of that. Got a fully working car right next to it, WITH cables . I guess I though when it is DEAD it is somehow different? I'll give it a shot, then maybe take a day trip to recharge it. :D

Great advice all!

Will any electronics came back messed up? like key lock or any of that? The top is down so I can get in to it. I know the radio will be DOINKED...

I bought a 987 with a dead Porsche battery that had been sitting for months. It was as dead as Abe Lincoln - it showed NOTHING, it had the same electrical capabilities as a tree stump . Charged it up overnight on my old 1970's era battery charger, and it's been working perfectly for over a year now.

You will need your radio code.

You will need to roll the windows up (with the top closed). Then push and hold each window switch for a few seconds to allow the closed position to be relearned.

To relearn the idle position of the gas pedal, turn the key to the run position (do not start or touch the gas pedal) until you hear the throttle click (about a minute). Then turn the key off for about 20 seconds and then start the car.

Hard to get TO the battery with a dead battery. Nice. Still learnin...... I'll try a SEARCH here

Gotcha. I won't be pulling that stunt again. :o

Last time I got locked out of the frunk because of a dead battery, I used the little connector on the fuse box for the positive lead and grounded the negative lead to the chassis, Push the frunk button and it popped. I used a motorcycle battery to power the operation. It worked quite well. Now if I'm going to not drive for more than a couple of days, I leave the frunk unlocked.

on my 987CS I was never able to open the front trunk following the factory recommended steps (through the fuse box) when I needed it.

but I read HERE :-) that applying 12VDC to the cigarette lighter, you would be able to open the trunk using the trunk button...

The first time I wrapped a Phillips screwdriver with electrical tape (to avoid possible contact with the sides of the lighter (grounded to the chassis) and only touched the center of the lighter and clamped the + side of the jumping cables to the top of the screwdriver and the negative side to the door hinge.

It worked so well, that I found an old 12VDC light assembly (with a connector for the cigarette lighter) cut off the light portion and used only the connector side and whenever in need you can connect a jumping cable to the open wires and open your trunk.. I keep this gizmo on the passenger arm rest compartment just in case..
.

Lead acid batteries are not meant to go below about a 50% state of discharge. At least not often. And in cars that very seldom happens. But once? Your battery should be fine if you charge it fully, i.e. more than just running it in the car for a bit. Put in on a good charger for 24 hrs or more.

Its not that the batteries are not meant to go below 50%, its just that deep cycling LA batteries reduces lifespan.
IIRC, LA batteries will last for 5-7 thousand charge cycles when batteries are only slightly discharged (~80% charged). Same battery good for 5-7 HUNDRED cycles when discharged over 50%.

You and Allegro are essentially saying the same thing.

Regardless it's good to know. I may have known that about LE batteries, it just hasn't occurred to me the way you both described it. Now it's more clear to me.

Just used a cig lighter cable and got the frunk open. It wasn't enough to start it though and wire started getting warm. Off to buy a slow charger. Batt looks very clean but no date I could find. Guessing I take both wires off while charging overnight, right? Get the self monitoring Battery Tender one.

I think I will replace battery. This Duralast 48-DL looks clean but that model was discontinued in 2013! I know this car was driven very little last 4 years, so, might as well upgrade to new battery. Thanks gang!

It sounds like you should replace the battery so good call. The battery is at least 6 years old and will fail over time. If you're using the cigarette battery adapter plug, you do not remove the positive and negative terminal cables off the battery. If you are pulling the battery out of the frunk and charging it out the battery tender via ring terminal harness or alligator clips then yes. You should remove the negative terminal first then remove the positive terminal. Vice versa when installing the new battery. You can always test the battery with a reliable voltmeter to see if it discharges a 14V range but I would just replace the old battery.

Hoping this AutoCraft AGM 850 CCA fits and does the trick! :D

Any other "recovery" I need to look out for?
Will everything work without the radio code that I have yet to chase down.

Everything will work except the radio, but do the above.