Have a 2005 Bentley GT and have been putting two trickle chargers on during winter, for each battery; however in looking under Maintenance in the Owner Manual it instructs you to connect the negative post of a donor battery to the negative post to the accessory battery (driver's side) and the positive post of the donor battery to the positive post of the engine battery. This is Fig 1-13 "Emergency starting battery connections".
So, is this how should connect the trickle charger and not use two?

 

Do you not have a battery charging point already built into the car? I thought it was standard fitment - on the side of vertical carpet in the boot (or trunk as I understand you like to call it in the colonies).

From that you simply need a single charger - most people use the standard Bentley branded C-Tek.

 

Not aware of connection will check out. so, if found, this keeps both batteries charged? Didn't see any reference in Owners Manual.

 

My GT has only been sitting in the garage for about 3 weeks now and it's already giving me low battery warnings when I start it. I tried to charge the battery on the driver's side in the trunk, but it says that it is full (it is 2 months old). What's the next step? I'm curious about this "battery charging point" and how it works.

 

Yeah you should have a cigarette lighter-ish connector that pops out of the side wall on the left side of the trunk. I keep my 2005 charged that way with the Ctek charger and everything's been fine for the two years I've owned it.

 

I have an 05 GT. I see from another response there should be a cigarette-type socket to plug into. I have not been able to find that. In talking to a Bentley service manager in Scottsdale AZ, USA he said that I could put the Ctek chargers on both batteries. that seems to be working.

 

The charging connection I mentioned is about halfway back on the left side wall of the trunk, about halfway up. When it's closed it's flush with the side wall, a little press will cause it to pop out and present the charging socket.

 

Thank you for the charging station location, don't know why I have never found.
Two questions: do you use a generic cigarette type plug in or is there a special Bentley adapter? Also, does this charge both batteries?

 

Hi - I use these products - Ctek charger and cig lighter adapter:

(unavail but there should be something similar) and


I *think* it charges both batteries. But the right-side battery hardly ever fails on people. It's almost always the left-side battery. In my 2 years with a Continental and 13 with a VW Phaeton (same electrical system) I've never had to replace a right-side battery. I've replaced a half-dozen left-side batteries. I don't use the charger on my Phaeton as that's my daily driver.

 

Unless the rear boot (trunk) connector uses some sort of an isolation circuit then I do not see how it can charge both batteries as one is a house battery and the other is a starter battery. You would not want to tie them together unless there is an isolation circuit that protects each battery.

 

You are of course technically correct about not connecting the batteries in parallel long term, but I suspect partially correct in this case:

The charger socket is wired without interruption to what VW calls the "Main Systems Battery" which is in parallel with the alternator.

The "Starter Battery" can be connected to the Main Systems Battery by means of a "Battery Parallel Circuit Relay" and a 300 Ampere fuse. That relay is pulled in by the Battery Management Control Module.

There is information about the relay switching strategy here: http://www.procarmanuals.com/vag-ssp...d-power-supply

Unfortunately it doesn't mention what happens during long term charging...

Finally, for anyone who wants to know what the charger socket looks like, just Google the connector part number JNV998131A.

 

Dark Green,

This is a fantastic explanation to say the least. My first take on the detailed explanation is that I still do not fully understand exactly how both batteries get charged by the plug but the "mystery circuit" that they describe apparently will charge both if the starter battery is below 11vdc. This circuit is not a long-term solution as it is temperature controlled but it would appear to work for the short term.

Thanks soooooo much for the information!

 

Deltran 1.5A Battery tender not good enough for this car? I have them on 5 other cars and they all charge to green light 100%. But the Bentley will only get to the 80% or higher charge state. Newish battery.

 

Strange, as like you I have them on all of my cars and they work very well. I have one on the Bentley and it works perfectly. I am using the 4 amp models on all of the cars. No problems.

 

I have all 1.5A models of Battery Tender, that might be the difference then