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Not a lot of need for a backup battery for the alarm since the primary battery is located inside the cabin of the vehicle. By the time a thief got to it to disconnect it - they're already in the vehicle and the alarm has proven worthless (as most do.. anyone here EVER call the cops about an alarm going off in a public place if it wasn't really annoying you?)
As v10rick says - it's a case of needing an automotive ELECTRICIAN. They're rather scarce on the ground. Mechanics are rarely good with electrical troubleshooting. The usual technique they use is to replace things until the problem goes away. That can get rather expensive quickly.
What needs to happen is someone who knows how to put the car in sleep mode, and correctly connect a good ammeter in series with the battery has to troubleshoot the system. Once they confirm there is an excessive standing draw - they'd narrow it down by pulling fuses to disconnect circuits. Once they find the circuit drawing current it shouldn't be - they'd further troubleshoot it by disconnecting modules and components from that circuit.
Doing this sort of work isn't cheap - but it's way cheaper then throwing money at unneeded replacement modules (that can't be returned since companies don't want people troubleshooting with their parts by ordering them - not fixing the problem - and returning them.)
You may want to ask the members of your local Porsche owners club (PCA in the US) who is good. If you were in NJ I have someone I could suggest - but since you haven't shared that information with us..
My issue with battery charge is that if I drive the car a significant distance every day (like 30 minutes or so with just 1 or 2 stops/re-starts) without skipping more than 24 hours or so, the battery stays charged and everything is fine. If the car sits undriven for 4-5 days, the battery discharges enough that the electric lift gate stops working... and the owner's manual says that's the first thing that stops working when the battery charge is low. I do not see the battery discharging when measuring current through the negative battery lead. When I lock the car, the drain on the battery drops to 10.7 milliAmps in just a few seconds. If I don't lock the car, the load starts at a bit over 10 Amps and drops in steps over 10 minutes until it finally reaches 10.7 mA. And the drain on the battery through the negative battery cable never goes above 10.7 mA. I've been waiting for a period of time when I won't need to drive the Cayenne for 4-5 days in order to recheck drain on the battery, but this time through the positive battery cable to see if some other system in the car that has a ground of its own (so the load draining the main battery would not be seen through the main battery's ground lead) is causing a drain on the battery that I can see through the positive battery lead. My intention with the first measurement using the negative battery cable was (negative being the safer option for testing this) was to find that I had a 1 or 2 amp drain after 24 hours or so, then pull fuses 1 at a time to find out which circuit in the car the load was coming from and take the troubleshooting from there. I'm not leaving this level of troubleshooting to a mechanic... it's too time consuming. I want to know where the problem is before I decide whether I need a shop to help with this or not. I am qualified... trained as an automotive engineer but American car manufactuers in the late 1960s and early 1970s completely killed my desire to be an automotive engineer (their sense of what was important and what was inconsenqential was horrible... I was reported to my boss for being seen walking down the hall of of the GM Design Center with my hands in my pocket! My boss said it made me look like I had nothing to do. I told him that, indeed, I had nothing to do until I got to the blue print room to get a copy of the blueprint I needed, and that as long as I was walking, I was doing everything required of me and asked who reported me and who his boss was so I could report to his boss that he was wasting my time, my boss's time, and the "reporters" time by being concerned about something so trivial. They didn't like that "attitude." And I didn't like their attitude so after getting my "dream job" working in the design center, they ruined the whole thing for me.) I did other engineering work for 34 years before retiring.
So there's no backup battery for the alarm system? If you kill power from the main battery, the alarm stops working immediately? Not like that on my motorcycle (I installed that alarm system myself) or 2 older cars... in fact one of them would set off the alarm when you removed either main battery leads if you didn't do something else first (I forget what that was at this point, it was quite a while ago). Also, the Ungo Box I had on my 911SC Targa stopped working after 15 years or so and I had to replace a secondary battery that was part of that system for the Ungo Box to start working again... including the alarm siren/whistle. I disconnected the battery to work on the Ungo Box and after replacing the secondary battery and arming the Ungo Box all hell broke loose because the main battery was still disconnected.
Just noticed Deilenberger's post (hadn't seen it before I posted my long reply above).
There is an independent Porsche shop in the next town (I'm in the suburbs 30 miles east of San Francisco) that has been there since the 1970s... they have a tech there who works on Cayennes a lot. I've spoken to him on the phone and he actually understands everything I told him about the problem without me having to repeat things ad infinitum and without having to explain the troubleshooting logic--he already understands the troubleshooting logic. I have had to figure out a number of things on my own, like how to put the car into sleep mode with the doors open so I can have the battery test going without having to close and lock the car which puts the car in sleep mode in 10 seconds or less. There is no visible interlock "door closed" switch, but I figured out if your jigger the door latch mechanism in the door by lifting the front-most "hook" then pushing it into the closed/latched position, it apparently makes an interlock switch inside the door latch mechanism. That allowed me to "lock" the Cayenne with the front doors open... which they need to be in order to get at the fuse blocks in each end of the dashboard. That's the easiest way to get the Cayenne into "sleep" mode for diagnosing where the load is coming from. As mentioned in he previous post. I don't see the load measuring through the negative battery cable so checking to see if there's a load through the positive battery lead could be more definitive. The same problem has happend with 2 batteries... #1 manufactured December 2015 was a wet H8 battery (databases for the Cayenne are often wrong specifying H8 as the replacement battery when the correct battery is actually an H9... H8 and H9 have the same battery post orientation, same width and height, only the length is different... H8 is 13.5 inches long. H9 is 15 or 15.5 inches long (can't remember which off the top of my head), the 13.5" H8 does not fit under the front-left-corner battery retaining bracket properly. So if you have a problem with your battery appearing to be too short for the left front retaining bracket, the only problem is all the wrong battery fitment databases are wrong... the H9 is really the battery you need. The second battery was made in May 2016 and is an AGM H9 battery. I replaced it only because of the size issue and because I wanted to see if a second battery behanved the same way in case the first battery had a problem, though a load test on the first battery indicated it was OK.
The process you figured out to put the car into sleep mode is exactly what Porsche describes doing in their diagnostics manual for the 958 cars - trick the car into thinking the door is closed by turning the door lock over (they suggest using a screwdriver to do it.)
I don't see that you'd find anything using the positive terminal vs the negative terminal. In order to drain the battery both are going to see the same current - one coming, one going. The only thing I can think might be different is the grounds you're measuring from.
I assume you're using an in-line ammeter (since you mentioned the 10A reading) and DC clamp on meters are still way expensive. If you're using it between the battery terminal and the clamp for the cables connecting to the battery - it won't matter, negative or positive.
The sleep value you give sounds fine 10.7 mA is low enough that the battery should last for a month or two before being discharged enough to even notice.
I dug through my old 955 manual and found the alarm system wiring diagrams. Three pages - and much of the system is built in as part of other components on the vehicle. It's not a discrete system like we used to install aftermarket years ago.. These diagrams are for a 2003 model 955 - so they may, or may not be applicable to your 2010 model.
Anti-theft diagram, page 1
Anti-theft diagram, page 2
Anti-theft diagram, page 3
One random thought.. the vehicle isn't left parked in a noisy environment, or somewhere that it might get buffeted by strong winds? There are noise detectors inside the vehicle, and motion detectors that might turn the system back on again.
Also - are the keys kept far enough away from the vehicle that they won't try to talk to it and wake it up? Stupid idea probably.. but we're looking for a real needle in a haystack here..
Thanks for the diagrams... have some work to get done tonight and Monday but will dig into the diagrams first chance I get... probably not radically different in the theft alarm from 955>957.
Thinking about a second load on the batter with it's own ground somewhere else... you'd have to see that load through the battery ground cable... If you removed the main battery ground cable, then powered the other circuit from only the positive battery pose, the other circuit would be dead... the other circuit would not have power until you pot the negative battery cable back on the battery... so thanks for getting me off that sidetrack... I just wasn't thinking clearly about it.
No the car is parked in the garage. Pretty quiet suburban neighborhood. I already set off the alarm leaving the dog in the car and not being able to remember where the button was to disable the mition detection in the interior. Had to go get the Thai food leaving the car unlocked (owner's manual was at home where I've been trying to get time to read through it... 300 pages in the general manual and another 300 or so pages in the PSM manual... seems like an excessive amount of documentation. Some day these companies are going to realize that if owners/users can't figure it out without a manual... it's too complicated. And why is the button to disable the motion detection in the inside of the door pillar instead of having 2 lock buttons on the remote fob (1 button locks with motion detection, one button locks without motion detection)? Thanks again for the diagrams.
If there isn't a security system battery, I need to monitor the battery over a longer period of time to see if the discharge rate goes up after 24 hours or 36 hours or something. I did a rough calculation that the 10.7 mA drain would take something like 80 days to drain a fully charged battery. Somewhere I saw something that said the drain on the battery should be 50 mA or less with the car in sleep mode, so 10.7 mA seemed like as good as it could get. But I only watched the drain for maybe 8 hours or so. Maybe that wasn't long enough. But having measured 10.7 amps (yes in series, though I do have a clamp-on meter also, only about $30 on Amazon, but you can't rotate the meter in relation to the clamp and the earth's magnetic field alters the clamped reading so if the meter moves even a little bit (rotationally), the measurement you get changes, I didn't find the clamp-on meter useful for this troubleshooting. My Fluke meter leads got really hot though... if you don't lock the door, the car pulls a little over 10 Amps for a couple of minutes and the leads kept getting hotter and hotter and started releasing a little of that burned electronics smell so I had to find leads with larger gauge wire that would fit the sockets in the Fluke meter... THEN it would pass 10 A without nearly melting the test leads. So I think if I can arrange a few days this week where I don't need to drive, I can just put the meter on it and measure it over time to see if there is a delay before any drain starts on the battery. Wish I could record the voltage over time so I could see what's going on without having to stand and watch the meter all the time. Will have to look for a USB multimeter that can handle up to 12 Amps of current and log to the computer. Then I could get the sort of results I need in order to move to the next troubleshooting step.
Re. key location -- Yeah, the whole family room and a wall with a brick fireplace in it are between the key and the Cayenne on the far side of the garage when the key is inside the house. Nothing happens to the Cayenne in the garage if you press buttons on the key fob in the kitchen where the key usually sits.
09-25-2016, 05:01 PM
