I have just removed the left side positive terminal battery assembly, and a 150 Amp Little Fuse fell out. I assume that it runs between the two bolt terminals underneath the top of the assembly. Is this correct?

 

Also, when the battery was removed, I discovered a black cable which terminated with a purple connector with many prong receptacles. Does anyone know its purpose?

 

What are the size and AMP HR specs for the starter battery? Original battery is wet but is AGM a viable replacement?

 

A little revival of this thread. Changed the battery on my 10 GTC Series 51 today (only specifying sub model in the case it makes a difference) a few pointers to save your sanity as I almost lost mine:
To modify the OP's instructions to replace the left main battery for a GTC; Sorry I did not take pictures
1. You MUST MUST MUST move the fuse box above the battery in order to remove the plastic piece (with the four main wires attached) over the positive channel. the OP's guide says you don't have to but on the GTC, the fuse box is much closer to the plastic piece. Without removing the fuse box, you cannot loosen the farthest screw (again as mentioned in OPs guide) and the plastic piece will not be able to lift over the positive channel.
2. To remove the fuse box there is a star key on the very top of the opening to access the battery. There was a fat wad of wires in front of it that must be taken out of the plastic zip tie like holder (best description sorry). There are smaller star keys in the actual fise box, but unscrewing those does not help, ONLY the one main star at the top will allow the fuse box to be taken out and pulled to the side.
3. I also got away with not removing the black piece on the side, (thank god because it seemed brittle).
4. Once you move the fuse box it is smooth sailing as you can actually see what yo are doing. For the GT owners who were able to lift the battery out, with the fuse box in there, that takes skill and I salute you.

As mentioned above numerous times, getting the battery out is SUCH A PAIN IN THE A$$. It is incredible how easy it is to remove the battery on my 2010 panamera turbo compared to this (being that it is the same year and same parent company).
Hope this helps

 

Looks like a OBD code reader socket .To plug a diagnostic instrument into .

 

Having some of these issues after having both batteries changed because rear window wouldn’t raise fully. Now car won’t start with normal cw turn. Will crank with ccw turn can be driven 30 minutes and car seems to have lost all power. Unlock manually and car will only start with ccw turn. Windows still won’t stay programmed after each start either. HELP!!!!
GT 2004

 

Sounds like the big LHS batt is not passing on it’s charge .
So check it all out ...connections and fuses .For the fuses don’t rely on the Mk1 eyeball use a multimeter.

 

Hello Mike,
Who replaced the batteries, as what you are describing make no sense as to a normal battery change, are you sure all connections are correct, did any of the mega fuses blow ?
Please post wide shot and close up shots of each battery area for us to check out.

Johnny

 

Hi
I just wondered how much of a fight was it to remove the battery because my one will not come out because the fuse box is so close to the top of the battery. I have tilted it at all angles but the fuse box is in the way every time.

Thank for ant help

 

​​​​​​Hello @Alan Stockdale ,
I gave instructions at post number 39, and again starting at post number 78 for the removal of the fuse box, 3 T-20 screws need to be removed to swing the fusebox out of the way.

Johnny

 

@Alan Stockdale ,
How did you make out with the battery change out ?

 

Never heard back from @Mike Brown ,
Any updates @Mike Brown?

 

After I replaced both batteries of my Bentley Flying Spur, I checked the charge. My conclusion is, against what was said sometimes, that the right Battery is NOT the starter Batter. The right battery is more like a backup battery. At cranking it uses the left Battery to start and for the housing in off and idle. The right battery seems only to be used under very specific circumstances, e.g. left battery drops under 10V and CCW procedure is used. That would also explain, why the left is the first battery that wears out.

CCW Procedure: (Counter Clock Wise Key Switch)key 1 time left - enables emergency procedure to use the right battery. Not sure what hapoens, for sure right battery is now charged but it is still not used to crank. At least in my situation where the left battery is good and does not drop below 10V.Following voltage measurements:Sequence was turned off, normal start (crank), turn off, ccw switch and start again. Nothing changed except the right battery was now charged.


The whole procedure before entering the car, open the car, start, during crank, after start in idle, stoping and after closing the car.
Right battery started charging but no signs of voltage drop during crank.

 

I know for a fact that this is not true. The car uses the right side battery to start. I know this because my car wouldn't start so I went out and bought a brand new left side battery (because it was bad). Got back and everything turned on normal with the regular CW turn and the car still wouldn't start...like it wasn't even cranking. I was scared that I was going to need a starter because it was acting like a dead starter. So as a last ditch effort, I put my jump box on the right side battery and it fired right up. I then went out and bought a right side battery and it has cranked everytime without the need for CCW turn. All the CCW turn does is activate a relay that puts the two batteries in parallel so that the right side battery can run electronics AND crank the car up. After starting up and a short delay, it disconnects the two batteries and that's why if your left side battery is missing or has ZERO charge, the car will die immediately.

And the reason why the left side battery wears out, is because it is running the electronics when the car is off, and it is susceptible to running down low on voltage if the car sits, as well as constantly cycling since its always running electronics. The right side battery cranks the car for 5 secs, then disconnects shortly after, so it gets very little use and lasts a lot longer.

 

Surely like a boat the CCA size would indicate if its a Cranking battery......