AW

Well it happened today. While driving back from the airport after picking up some family my Cayenne front left tires suffered a major flat.

First the car felt out of alignment. Soon it felt like it was experiencing some power steering failure. I pulled over on the right side, to discover an almost flat tire...

I tried to fill it with some air, then tried the glue thing which did not work. I have finally called my wife to help with my passengers and a tow truck. I ended up home 5h later with some brand new tires.

I don't think I'll buy an SUV without spare wheel again.

AW

Gert

The spare tire is now an option and it is also something one can retrofit.

JFScheck

I wouldn't either, that's why I ordered one with mine. I would consider the retrofit...

AW

Is the retrofit placing the wheel outside of the car or somehow inside?

Thanks.

AW

philg3

The problem with the retrofit, as I understand, is that you lose the second battery. In addition, if you have the large Bose sub that was in the early 03/04 production vehicle, don't you have to replace it with the smaller one. Of course, you can get the external one, but it gets in the way, looks bad IMO, and reduces rear visiblity. I wish I had a spare, but I prefer having the second battery. Of course I haven't gotten a flat yet.

thecleaner

AAA !!

jamy85

The Bose sub is relatively small around 5 by 4

356driver

I had the collapsible spare added to my 04 CTT when I bought the car. It fits nicely in the spare tire compartment. The wheel goes on top of and around the sub-woofer. I don't know about the second battery - newer Cayennes don't have it so I'm not sure it's that important.

pdxjim

Having put 20K miles on 03 S (with two batteries) and 15k miles on 05TT with spare tire, I can report that I have not had any flats (touch wood) and the single battery has performed flawlessly (even in -4F weather, parked outside for a week). So, IMHO, I feel more comfortable with the blow-up spare than a spare battery. What I do like is the TPM which alerted me to a slow leak caused by a nail.

PS. just filled out a survey on the Cayenne, and they asked questions about extending the truck for a 3rd row, hybrid engines and other ideas.

996FLT6

AW-I think I saw your car. Was it on Highway 280 heading south?Mike

Cay-ute

Gert, I have an early 03, with second battery and large Bose, how does one retrofit the spare. I bought the spare and am a little tired of hauling it around in the back compartment

bullbear

Sorry for the ignorance but what's the 2nd battery for?

ltc

From a previous post (rennlist search function is a wonderful thing), compliments of rennlist user "Difference Engine":

Now for some reason, Porsche doesn't supply a manual to techs that explain vehicle systems. Short of going to the actual shop manuals, there is no concise explanation of how things work. Volkswagen does however provide a Self-study Program. In talking with our techs, who have been on training for both Cayenne and Touareg, the electrical systems of both vehicles are identical. The following info is taken from the "Touareg Electrical System Design And Function" portion of the "Self Study Program Course #89J303."



In this electrical system, one battery, the starter battery, ahs the role of supplying the starter with power and, if neccessary, also the electrical consumers required for the starting procedure (start-up consumers). The second battery, the on-board power supply battery, provides the rest of the electrical consumers with power.

The batteries are connected in parallel.

To prevent the starter battery from becoming discharged by too many electrical consumers, the consumers are split into two categories: start-up consumers & on-board consumers.

The start-up consumers and the remaining electrical consumers are supplied from the on-board power supply battery. If neccessary, these consumers can be supplied from the starter battery via the Power Supply Relay 1. Consumers that require a large amount of energy are always supplied from the starter battery.

In addition, both batteries can be connected via the Second Battery Charge Relay to charge the starter battery.

The actuation of the relays comes from the Vehicle Electrical Systems Control Module. It monitors the voltage of both batteries whenever the ignition is on and can thus detect when the starter battery needs recharging.

Standby

The system is on standby when the Vehicle Electrical System Control Module is in sleep mode. If on standby, Power Supply Relay 1 and Second Battery Charge Relay are open. Power Supply Relay 2 is closed.

Starting Procedures

When the ignition is turned on, the Vehicle Electrical System Control Module is activated (wake-up mode) and evaluates the state of charge of the batteries. If the voltage reading of the on-board power supply battery is below 10.5 volts, it is deemed to be discharged.

The starter battery is considered discharged if the voltage reading is below 11.5 volts.

There are four different conditions that can be detected before the engine is started depending on the state of charge of the batteries:
-On-board power supply and starter battery both charged
-On-board power supply battery discharged, starter battery charged
-On-board power supply battery charged, starter battery discharged
-on-board power supply battery and starter battery discharged.


Over the next few pages, it describes the starting procedure for each of the four above conditions. Long story short, the Power Supply Relays 1 &2, Second Battery Charge Relay, Access/Start Control Module, and Vehicle Electrical System Control Module are constantly measuring voltage in the two batteries and are switching and transferring power as needed.


Now for charging:

Two-Battery System Charging

Charging

The on-board power supply derives its power from both batteries which are connected in parallel and protected against overload by Power Supply Relay 1.

Charging of the on-board power supply battery

The on-board power supply battery is charged continuously.

Charging of the starter battery

Charging of the starter battery is controlled bythe Second Battery Charge Relay which is activated by the Vehicle Electrical System Control Module. The normal charging time is 20 minutes. After this period the Second Battery Charge Relay will open.

if the starter battery voltage drops below 12.8 volts, a new charging cycle of 20 minutes maximum is started.


Not sure if that answers any of your questons, but it may help in understanding how the system works.

One of my customers with a dual-battery Cayenne S left his vehicle for 3 weeks while on vacation, and upon hs return, it started with no problems. I have no idea how long it would take to completely drain the system.

AW

Yes that was me. I noticed your car because we have the same color... small world!

AW

Cay-ute

Bullbear, ITC did a great job of explaining the dual battery system, while it is a tremendous inconvenience for storing the spare tire, it is absoutely wonderful for ensuring that your Cayenne has power should something go goofy with the starting battery. For example, when I first added XM to my Cayenne, the installer did not understand the power system and installed it on a circuit that required a switch to cut off power to the XM unit. When I failed to pay attentiion to turing the circuit off, the primary starting battery would run out of charge. When the primary battery failed to start the Cayenne, I would turn the ignition switch via the key all the way to the left, that brought the second battery on line to start the Cayenne. I have had this happen about 20 times and each time the second battery would get me going. Subsequently, I have had the XM power changed to a switched circuit and the issue of draining the primary battery has gone away. However, I have learned to love the second battery despite the fact that my spare (collapsible variety) sits in the rear cargo compartment. The best of all worlds would be to have the spare in the spare area, the second battery and the Bose subwoofer/amplifier. Not sure if I can get there, but I am looking to see if it is possible.