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986 Forum - The Community for Porsche Boxster & Cayman Owners (http://986forum.com/forums/index.php)
-   Boxster General Discussions (http://986forum.com/forums/forumdisplay.php?f=5)
-   -   left lights on, killed batt. Charge or replace? (http://986forum.com/forums/showthread.php?t=75984)

Allegro 08-19-2019 04:08 PM
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.

dghii 08-19-2019 06:30 PM
Quote:
Originally Posted by Allegro (Post 601305)
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%.

piper6909 08-19-2019 06:56 PM
Quote:
Originally Posted by dghii (Post 601315)
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.

wwjd 08-20-2019 04:44 PM
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!

1PorscheBoxster986 08-20-2019 06:55 PM
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.

wwjd 08-22-2019 02:06 PM
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.

Paul 08-30-2019 06:31 PM
Quote:
Originally Posted by paul (Post 601182)
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.
Everything will work except the radio, but do the above.


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