Another 987 Battery Drain Thread!

I picked up my 2011 Boxster back in August of '24, and I'm generally pleased as punch with it. The car is my fair weather daily - as in, if I can't drive it with the top down, I don't drive it. It gets left in the garage for the winter (4-6 months, depending on the weather). Anyway, it has one issue that seems to be relatively common: the battery will drain to zero in a relatively short time. Last time that it happened to me, it took only 4 days to get to zero volts. I now hook it up to my NOCO Genius any time I think it might sit for more than a day, and when garaged I always leave the front trunk lid popped because getting into it with a dead battery is a pain in the ***, as many of you know. My last discharge incident got me to hook up a multimeter between the battery and the negative cable, just to see what the baseline draw is. Turns out, it isn't much - less than 10 milliamps if I'm reading things correctly. This makes me think that the battery (a conventional Duralast manufactured in 2023) may no longer be holding a charge as it should. But I'm not a battery expert, so I just don't know if it's worth replacing. I did install a battery monitoring gizmo, and it does show that the voltage steadily drops until either the car is started, or the Genius decides that it's time to start doing its thing. Or it just dies completely. I've checked out several of the most recent threads here dealing with this issue, and in one of them a helpful commenter indicated that complete discharge of a lead-acid battery can (and indeed does) lead to irreparable harm to the battery . This leads me to think that my current battery was probably in less than stellar condition when I acquired the car, despite being less than a year old. Have any of you other Boxster - or Porsche -philes been through this kind of thing and had your problems go away after replacing the battery ? That said, as soon as I have more free time I'm gonna start reading up on automotive battery technology, care and maintenance.

I’d replace the battery , continue the use of the NOCO for the quiet periods and then reevaluate whether it has a parasitic battery draw another time. It’s very possible idle time with an already failing battery is all that happened.

Yeah, I'm coming around to that idea. I just wish that I knew what got the battery to that (damaged) state before I had the car.

I installed an AGM H8 size battery on my 981 and leave the car under a seal skincover for more than a month and never have had an issue, true the H8 is the largest battery you can fit (and the heaviest) but the piece of mind is priceless.. BTW Costco sells the Interstate AGM batteries for $180 with 36 month warranty. .

I will check them out, though I'm not a Costco member.

You mentioned you have a NOCO , repair mode is not automatic. You hold the mode button for three seconds it will shift position to the flashing red 12V battery repair indicator, then you let it run, when it concludes it will shut itself off.

Now I don't even have to open the manual! How will I ever learn to do things for myself?!?

RSchwerer said: I seem to remember that our cars have lower parasitic draw when stored locked. I'll second that. I destroyed the battery in my 987.2 by leaving the car unlocked in the garage when it was not being driven for long periods during Covid. Now I lock it whenever I park it, regardless of how long I expect it to be before I use it again. The battery is much happier.

Get a battery tester before you shell out for a new battery . 10ma should not flatten a healthy battery , so it's probably that the battery has had it. Trust...but verify. When I had a 987.2 , I found the car would last MUCH longer when not in use if I locked the car. I guess the car goes into a "deep" sleep after a few days. In order to unlock the car, you MUST first tug on the handle to wake the car, then you can use the fob to get in.

Take your battery to a shop, or Batteries plus and have them do a load test for cold cranking amps. That will tell you if your battery is weakened and needs replacement.

It's handy to have a battery testing tool and is easy to use. This one will report battery remaining as a percentage. Seems to work well for me. Battery Tester

The Battery Tracker app is confirming this. I normally leave the car in the garage, unlocked and with top down - and the app shows a noticeable, steady voltage drop. Yesterday, I cleaned and "conditioned" the soft top, so I just left the car like that (top up but still unlocked). The voltage line has now been nearly flat (little or no voltage drop) for almost 24 hours. I locked it after seeing that, and I'll check it again tomorrow when I go to work. I can only guess at what systems might cause this, because it doesn't make a lot of sense to me. Is it the factory theft deterrent? Edit: After another six hours, the battery voltage hasn't dropped at all. The App will hold data for 30 days, and my only worry now is that the battery voltage does seem to drop when the car is parked at work (top up & locked). I'm going to continue to watch this. I did run the NOCO "repair" cycle since my last day at work. Maybe that changed things? Whatever the case, I won't be buying a new battery just yet.

This is the device that was suggested to me, and is now stuck to my battery . Amazon.com: Antigravity Battery Tracker Bluetooth Monitor System BTR-2 for 12V Lead/Acid Vehicle Batteries, Test Voltage Cranking Charging : Automotive

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I removed the front trunk light bulb so that it wouldn't drain my battery when opened for a length of time.

I wrote: I destroyed the battery in my 987.2 by leaving the car unlocked in the garage when it was not being driven for long periods during Covid. Then bofus wrote: 10ma should not flatten a healthy battery , so it's probably that the battery has had it. I agree. The battery failed after six years. So it was already near its end-of-life, but it was still working well until I parked the car unlocked for four months. That's what pushed the battery over the edge.

To deal with that, leaving the frunk lid popped open, I installed a small rocker switch to control the frunk light. Easier than removing the bulb every time, and it helps to use it even when I’m fussing with the battery or doing some detailing in the frunk area.

What is a NOCO ??? And why do you need one? My 2005 987 has been going strong since new, with a few battery replacements, and recently sitting in the garage for long periods (sometimes 6 months or more). What is a NOCO is the real question.

A brand of battery chargers and maintainers similar to CTEK.