ADias

Yes, stock 997.2s have steady debit of about 45mA while sitting - about 1Ah/day.

Regarding battery maintainers we should use current designs like the CTek. These have proper charging safeguards, older designs do not have.

911andchips

I had a battery with similar symptoms. Turned out it was low electrolyte.
In fact one cell was nearly empty. I didnt bother to refill as it was OEM just replaced it.

CAVU

For the sort term, your trickle charger is probably fine. I have a number of quality battery chargers for different purposes (Odyssey, Battery Tender and Schumacher) . One of my Battery Tenders would have been perfect but they stay occupied so I pulled the trigger on a C-Tek (OEM for the Porsche branded chargers), hardwired it direct to the battery and have had no issues with my wet cell battery.

It might read 12.7 right after disconnect, but 15 minutes later...? Part of the health of a battery is its voltage, not total health. The voltage can be used to tell you approx capacity remaining.

henkinc

So I got 12.7 V after the trickle charger turned green (overnight); I fired up the car and at the initial (somewhat faster) idle it read 14.4 V; after I tuned the car off it read 12.7. 40 minutes later it read 12.68. I suspect it may drop to 12.3-.4 in a day or so. All electrolyte levels are the same and cover the cell material. Radio works with USB port. All systems go.

One of the web sites you folks referred me to suggests a battery holding at 12.4 V is something like 80% effective.

My only base untouched is how the voltage holds under full AC load at 2k rpm, a test I can do anytime at the local Advance Auto. I suspect this battery will pass withy flying colors.

Thanks for all your help, guys. I should have done these tests weeks ago and never thought about it until OI thought the USB port issue might have a battery root cause.
Charlie

henkinc

I lost the thread now where the subject line was recommended by one of you on this thread. As it turns out, if I lock the car, even after 3 days not driven it stays at 12.5+ Volt with a drop maybe 0.01 V per day. (Yes, 0.01, hardly measurable - 12.52 to 12.51.) Clearly within margin of error for temp whatever. If I do not lock the car I previously found it dropping to 12.3 after a few days. Thanks for the tip, whoever you are!
Charlie

SDPorschelover

So bought a 2017 CPO 911 in October. The PASM and steering responsiveness did not seem up to par - I was concerned. Last week my battery died, replaced it under warranty from Porsche and low and behold the car handles better, PASM is more responsive and the electronic steeing is tighter and more responsive. Crazy how much these cars are dependent on electronics. Moral of the story - replace the battery even before it dies!

sandwedge

All I can say on this subject is that the batteries on the 997's I've owned have behaved different compared to any other car I've owned. Car cranks strong as if the battery is brand new. Then the next time you turn the key you get that sickening clicking sound indicative of a dead battery. Have had the same exact thing happen three times now. No slow cranking or anything else. Just went from what seemed like a perfectly healthy battery to a dead one with absolutely no warning.

So if you're down to having to charge the battery and limiting the use of your radio, my guess is that your battery is on borrowed time and based on my battery experiences with these cars I'm surprised you've gotten to the point you're at.

MarkinMD

Thanks for the insight, Sandwedge. The Porsche battery installed new when I picked up my CPO 2010 Coupe will be 7 years old in March. Even though I keep it on maintainer when it is parked for more than a week, I think I'll replace it real soon...

Another 911 battery story...I test drove a 3-year old 996 many years ago. The car started fine, but after driving for a few miles on the freeway, the instrument panel lit up like a Christmas tree. Every warning light came on. I happened to have the Porsche dealer's service manager in the passenger seat. He said, "Oh, that's just the battery...they always do this after sitting on the lot for more than a few weeks. We don't have enough battery maintainers for every car on the lot, so we replace a lot of batteries."

bheit1

A couple guys on YouTube swear by the Topdon Artibattery 101. It's a small box that works on nearly any modern car battery and does a bunch of tests, including CCAs, shorted cells, voltage, alternator, even a starter test. $50 at Amazon. Mine was supposed to arrive today, but we haven't gotten mail in two days. Before running out and buying anything I'd clean the battery connections, especially the ground to the frame.

Antigravity

Hey everyone, we have another little helpful tool in our Battery Tracker if you're looking for something to monitor your battery's performance. It has the cranking/charging tests and a nice feature for a scenario like this in the data storage where you can see how the battery is holding it's charge over the course of 30 days so you can see if voltage is dropping quickly or if there is an existing parasitic draw as well as the charging system profile as a whole over the course of each day. Pairs up and displays the info on your phone via Bluetooth so it is extremely easy to use! Feel free to check them out below and as always let us know if you have any questions.
Battery Tracker Lead/Acid
Battery Tracker Lithium

GTSpure

Hello friends,

Like many of us, I also use my Porsche mostly on the weekends.
Given this, my Porsche is often parked in the parking lot for over a week - without starting.

Unfortunately, my parking lot does not have a power source so I cannot charge the battery using the CTEK charger.

Can standing for a week / two without starting cause damage to the vehicle / PDK assemblies, etc., or is the main damage that my battery will die and I will have to replace it?

What are my alternatives in a situation where I do not have a power source to charge?

1. Is there a battery charger on the market (such as CETK) that runs on a battery (rechargeable)?
2. Can a one / two week parking without starting start to drain my battery?
The battery I have in the car is VARTA blue dynamic Year of manufacture 3/2020 Specification:
12V 80Ah/630A (EN) / 650A (SAE)/440A(IES) VR2-080R-0D1 12V

Have any of you experienced a product called "CTX BATTERY SENSE" or Antigravity.
It seems to me can be a wonderful solution to monitor the condition of the battery - and once the charge goes down it is a great opportunity to drive in the mountains and charge the battery

Thanks

sandwedge

The short answer is yes. But one week without starting it shouldn't be a problem with a healthy battery. Same for two weeks. I've done it. Where you run into problems is with an older battery nearing its last leg. As I said in a previous post, my experience has been that they give no warning they're near death. Strong cranking one day. Next day nothing.

Sounds like you're not parking in a garage so the solution I'm using may not appeal to you. I just disconnect the right battery cable, stuff a rag or whatever over the frunk locking mechanism where it can't be locked. This way you won't have any drain when the car just sits and you'll have assured access to the battery. I assume you don't keep valuables in the frunk when you leave it sitting outside for weeks . When you're ready to drive it again, just reconnect the battery cable and you should be good to go. Takes about 2 minutes...if that.

Only concern here as I see it would be with an old battery about to croak. No matter what you do, if it sits for a week or two even with the battery disconnected it also doesn't get charged so you could still have issues, again with no advance warning.

Joan Alcover

For those who wonder how long the car battery can sit without being recharged ......
..... and still have enough juice to start the car ......
..... Here is an interesting and useful post:
https://www.themechanicdoctor.com/ho...ry-sit-unused/

GTSpure

Thanks bro for your answer. As for the first part it's a slightly stressful solution I would say
Luckily I drove yesterday with my Porsche after about two weeks (an unusual situation for me) and it started smoothly.
It reinforces what you say. Like you I also think that as soon as the battery starts to show signs of weakening immediately replace.
The question - whether there is a product that connects to the vehicle's lighter / battery that can be used to check data on the condition (life) of the battery (other than charging).

GTSpure

Thanks. Interesting article