I keep my 08 FS on a tender, as I do not drive it every day. I noticed oneday when i did not put it on the tender for about 3 days when I went to openthe car, the auto un-lock would not work. I used the key and tried the push tostart. No juice. I performed the emergency start by using the key and turningit to the left. Car started right up, dash said low battery. I just had both batteriesreplaced less than a year ago. I also notice intermittently that the cruiselight comes on orange, and will not allow cruise control to work. This issue intermittent,sometime is works fine. I also noticed maybe twice that the infotainment systemwould restart. I noticed because I turned the heat off, and noticed the systemrestart while the car was running and turn the heat back on. I have not seenthis issue as of late. Has anyone else seen any of these issues? anything I cancheck? Car is going in for service Saturday, so hopefully these issues arerecorded and my tech can easily resolve. 98% of the time the car is fine. Anythoughts?

Thanks

Andre

 

Hi Andre,
The best battery maintainer to use for The AGM battery in your Bentley is Made by Ctek.
Low voltage affects the electrical system in many ways and will show low voltage faults in many modules. If your Mechanic has the Ross tech VAG-COM system to diagnose your car, he will be able to read every module and check all the fault codes stored. Witch battery maintainer are you using now?

 

Purchased battery maintainer directly from Bentley. Has bentley logo on front, and custom plug that attaches inside the trunk.

 

I would have your mechanic check the connections at the plug and test the operation of the charger.

 

If possible get it on a proper Bentley diagnostic computer. I have had one or two similar issues and when interrogated the car terminal 30 had a fault. Intermittent. ie bad connection. As it happened Bentley dealers fixed the issue for me.
Frank

 

Fully charge the batt first and see if the prob goes away. The car is so power hungry and gives off many codes if volts ain't high enough.

 

Just to clarify -- I don't think any of the Bentley branded CTEK chargers are specifically made for AGM batteries unfortunately (please correct me if wrong). I have only seen ones that say "lead-acid" on the side (both for older screw and newer magnetic connection ends). That said, the non-Bentley branded CTEK chargers (ie 7002) can be set for AGM battery charging and are the best.

Doesn't matter an awful lot, but frustrating none the less.

 

Looks like the Ctek multi US 7002 has the same label on the side of it
(Battery charger for 12V lead acid batteries)
if you are correct,then there are a lot of Bentley dealers selling the Bentley brand Ctek for all Gt,Gtc,Flying spur models across the USA. Like item # 251485213532 from Miller motor cars. (Bentley dealer CT)

 

Great point-- the regular ctek ones (not bentley branded) say it too, even those that let you select an AGM battery charge mode. (text is clear on 23124841729) I wonder if the bentley branded one defaults to AGM when charging then? If so, I'm getting a CTEK one to replace the "big box" bentley charger I currently use. Without being able to select agm like i do on the regular 7002 ctek connected to my corniche (didn't come with a charger port), I always figured that without the option, the bentley branded ctek defaulted to regular battery charging not AGM charging.

In the end, I suppose even an AGM battery is lead acid...

 

if you have a couple of cars and don't mind connecting the charger clamps to the battery of each car. The Schumacher ship n shore battery charger is a great deal for the money.
Real simple to use,fully automatic with all the mode switches on the front panel. I have used them in my shop for years and they have never failed yet. Ebay has them listed for 65.00

 

Aren't the two batteries different? I always thought the starter battery was the regular (i.e. lead acid) and the "house" or main battery was AGM? If I am correct, does this suggest you should use a different charger/tender for each battery? My lead acid CTEK is plugged in via the appropriate male plug into the socket in the trunk, which in turn deals with both batteries. I don't drive my car over the winter and have not had any battery issues using a standard CTEK in the described manner.

 

Yes, you are correct. The starter battery is a lead acid battery(passenger side USA cars) and the Main system battery is an AGM battery (drivers side USA cars) but when you connect your Ctek charger to the car it is only charging the Main system battery. The starter battery is isolated and charged through the Battery management control module witch has an internal converter that charges at a higher rate. The Main system battery is charged directly from the alternator.

 

Since my CTEK is only charging the AGM (main) battery, is there any problem with using the Lead Acid type CTEK? Also, when I use the diagnostic (e.g. VAS 5054) computer, is it drawing current from the main battery or the starter battery? I have had starting problems after a couple of hours on the diagnostic computer (even with the CTEK plugged in). I really appreciate your expertise and your willingness to share info.

 

The Ctek charger works well as a battery maintainer but when using a diagnostic computer, it is best to use a charger at a 6-10 amp rating. The Ctek is good up to 3.3 amps. When performing a flash on a module with the Diagnostic tester like the infotainment screen update,or parking brake module update,it's best to use the Snap on charger model # EEBC500 witch will keep the voltage at a constant rate and is recommended for all module programming. The starter battery is always isolated and its only used to start the engine only.

 

Thanks for the update. From your info I conclude CTEK lead acid charger is OK for maintenance charging of the AGM battery (house battery) AND the starter battery (indirectly).

If the house battery was weak, would it draw any currrent from the starter battery or, as you say, is the starter battery isolated both ways? I'm trying to understand how a computer diag session would cause the car not to start off the starter battery. This has happened more than once. Eventually, I replaced the starter battery as it wasn't holding a charge. A year prior, I had replaced the main battery. Both batteries that I replaced were about 5 years old (from what I could ascertain from the dates on the batteries that were in the car when I purchased it in 2011)