Hello

Did not find that here with a quick search so perhaps it can help some of you .

Had my car in the garage and on the original charger vor few days, did not use the car much over the last week. Batteries are from 2015. Today, no start possible. Light, Radio etc. all fine but no Start, just a "CLICK". Tried the emergency start with the key 2x left, then start, nothing.

Servicemobile from a friend came and we tried to jump start it from the engine bay (left cable of you are in front of the engine and you have removed the left filter-box). --> No change, also not while trying to to the emergency start. So removed some parts and got to the starter battery in the trunk, put the booster there, tadaaaaa, it worked.
So I get a new starter battery now and while then use the original charger AND the ctek that goes directy on the starter battery. I always thought the original charger does something for both batteries but I think that is a bad thought...

Have a good day

Richard

 

Yes, these two batteries are on separate circuits. The jump terminal under the hood is main battery and not the starter battery. When you're completely flat, use the jump terminal under the hood just to open the trunk as you came to find out.

I keep my batteries on Cteks when the car is standing still. So, I'm either driving it or parked. When parked at home, it looks like this:



The 7002 goes directly to the AGM main battery (not through the cigar socket); the MXS 5.0 goes directly to the starter battery. 7002 is set to AGM setting, the 5.0 to the lead acid setting

 

Cool, learned something new! Didn't realize the factory Bentley CTEK wasn't charging the starter battery.

 

Hello Sam,

The batteries stay on separate circuits. The starter battery is used solely for starting. The main as it's called runs all of the car's systems. The under hood access point is a direct back to the main battery and why it had no impact when, in the first post they tried jump starting the car that way.

There is one condition when the two batteries find themselves in a momentary parallel state, and that is through the ignition circuit when a certain sequence is exercised with the key. What that does is activates a relay (J581) in the trunk that puts the batteries in parallel connection so that you can use the main battery temporarily as a "jump" in the case of a dead starter battery. As soon as the engine starts, that relay is de-energized.



I cannot answer what Bentley was thinking even selling a (CTEK wrapped in a Bentley logo) battery maintainer for the main battery. I guess they thought it would be too complicated using two maintainers in a battery maintenance kit. Then when the starter battery dies, and it probably always will if the main is maintained and starter is not, the crossover jump feature solves it.

AGM and lead acid batteries charge differently. AGMs need a lower voltage deeper charge than lead acid.

 

Thanks again Bwings, Great info on the relay!

Yep, I knew about the 2 batteries and one being AGM. (similar to my boat setup, with a starter and 'house' battery, but that has a manual selector that allows switching and a 'both' selection for emergencies or charging both/equalizing them)

What I didn't know is that the only time the continental's batteries were in the same circuit was during the emergency key turn maneuver and was always under the mistaken impression that the supplied CTEK maintained both. Never dawned on me about the different charging needs, even though I specifically bought an AGM specific digital charger one of my other cars (optima red) and the boat's house battery (optima blue). I'm wondering if the blue top might be a hybrid though like some of the renogy batteries, but not sure.

Between not having a maintainer hookup for the AGM battery in the trunk and those little 'incendiary' mega fuses over the main battery terminals, it is indeed a funky setup.

'Typical' VAG group engineering though, lol. My long gone '86 Audi 5000s had the battery under the rear bench seat and my Q7, under the driver's seat, both requiring the seats to be removed. (not unlike the emergency trunk latch on the conti's)

 

Interesting discussion. I had the no start condition twice today. Kept pushing the starter button and it eventually started and I got a low battery warning.

Opened the left side battery cover and found a VW Start/Stop battery installed when owned by previous owner. So I thought that was the starter battery - even though I know the car does not have the start/Stop feature. Your diagram straightened me out before I could open the Owners Manual. Starter battery is on the other side. I'll take a look.

 

So I did a load test on the starter battery and it has 12V but won't carry a load. It needs to be replaced. What size and type do I need? AGM I assume.

 

I have Bosch batteries in mine. An S6 AGM on the main (leftside) and an S5 lead acid on the right. These are the typical sizes and types for the car requirements.

Others have made different brand choices.

 

Great. Thanks a ton.

 

My pleasure....We'll have to talk Vettes someday. My list:

59 283 Vette
81 350 Vette
09 C6 Vette A&A V3 Si-Trim

The 09. I did the build and the tune

 

Looks powerful! I've got my C6 for sale to make room for a C8. But waiting until 2021 model to give Chevy a year to get the bugs out.

BTW on the starter battery any reason not to use a AGM on that side?

 

No reason not to use an AGM as far as I know. Will probably do the same if I own this one long enough to replace it.

At the time of this pic I was 620hp, eventually went to 800 with meth and pulleys and other stuff then got bored and sold it. Everything with me was about mastering HP Tuners. But alas, we wound be doing that too much with the C8 and the E99 ECU.

The C8 is a winner. I attended the road reveal tour here in Phoenix.

I've posted here in the American Muscle forum. It is a very slow forum, but wish I could fins some tuners out there.

 

Just ordered my battery for pick up today. One more thing to confirm though - If I'm just changing the starter battery is it necessary to disconnect the ground on the other battery?

 

I do not have experience deviating batteries outside of the factory process, so sorry, I cannot answer that. There have been a number of others who didn't even know the process and just went for it and disconnected terminals in no special order. Most seem to have made it w/o issues, but because of the pyro device on the starter side, I am unwilling to risk even guessing. Remember if you remove all power the steering angle realignment needs to be reset...unless you position the steering wheel precisely straight forward before battery disconnect. Then it seems to wake back up in the correct place.

Frankly, one of these days I am going to figure out how to rid my car of the pyro device and do a disconnect workaround.

 

I kept my Ctek in "supply" mode throughout the entire battery replacement process and did not have to do any resets at the end. Otherwise typically followed the instructions. But I just removed the negative cable from the main battery and for some reason the instructions seem to say to remove both. I used an Advance Auto Gold size 47H5. Had excellent ratings and is a bit more powerful than the Bosch. Only 3 year warranty though. Bosch is 4.

Learned a few things that were not totally covered in the battery replacement instructions. Like there is a black metal bar holding the bottom of the battery in place. Also I believe the battery I took out is the original battery installed in 2008.

Finishing up I found a cylindrical black plastic sensor of some sort next to the starter battery negative cable. It was just hanging loose. There is a round hole in an extension to the negative cable and I assume it is supposed to be fitted in there. I couldn't get in in that hole though. Any idea where it goes or what it does?