OK, so I am on a steep learning curve with my 09 GT, which I have had for 2 days so far!

I had an issue with the window shuffling up and down on its own yesterday. I reset the windows and I think that sorted it. Today I put VCDS on and saw a load of errors (and no response from the transmission) but most importantly noticed the battery was at 11.5v!

Its odd as I drove a good 2.5 hours after buying the car so would have thought the battery should have been charged. I can only assume that maybe the window shuffling has drained it... or maybe the low battery voltage caused the windows to go loopy. Chicken and egg!

I have put a charger on and it's been sucking up current for a few hours, 15A initially now down to 6A at 12.8v.

I will see how it behaves overnight BUT if the battery is dying, I will get an new one.

It's got a Varta AGM 000 915 105 CE. I checked Varta's site and they are suggesting a 595 901 085 G14 Silver Dynamic AGM. Does that sound right? It's 95Ah 850 CCA so slightly higher capacity.

Any other AGM batteries I should look at?

Cheers!

(Sorry for all the posts but there are a few things that need sorting out on this car! Nothing serious but I want to get it 100%)

 

I don't think you have Walmart over by you but I get the cheapest H8 sized (Group 49) that I can, usually around $110 US dollars for the house battery. H6 IIRC for the secondary. They last 1-2 years and I get a new one under warranty. My car seems to eat through whatever battery I put in, AGM or standard lead acid.

They're so easy to replace, that this is completely worth it..and the Everstart at Walmart is the same as an ACDelco Professional.

 

Hi Rob,

Was wondering if putting a wet battery was OK?

The AGM Varta is £190 here. (240 bucks)

I use AGM batteries in my military vehicles and they last years and years, even with very little use. (You can sit one in a vehicle for 2 years with no charger and it will still crank when you need it to)

Not sue if our battery size coding is same as yours, but a cheap wet battery size 019 is £95 (120 bucks), with a 3 year warranty.

I don't know why Bentley would have one AGM and one Wet battery in the GT?

I'll see if I can find the date code on the AGM I have in the car at the moment. I suspect it has a shorted cell as its still sucking current and self discharges quite fast.

 

You will learn that the Bentley will need to be either driven daily or kept on a battery tender.

Group sizing must be different. I use wet batteries as they seem to last the same as an AGM style. I like the warranty.

 

After a look through the service history on mine, it appears to be ready for it's 4th 'home' battery! So one every 2.75 years... Just inside the 3 year warranty.

I wonder what its doing to them?

 

I'll suggest this is a strong possibility: "You will learn that the Bentley will need to be either driven daily or kept on a battery tender."

 

My Phaeton is my daily driver and it eats left-side batteries the same way. I've replaced 2 in 3 years.

 

Good topic for discussion. I'll offer that I own 4ea. Bentley Continentals: '04GT, '05GT, '07GT, and an '08GTC. I'm my own wrench/ a do it yourselfer and I only take a vehicle to a shop for the stuff that I'm not set-up to do... which is very rarely (ie: last resort). All 4 of my Bentleys I purchased used, and all 4 had dead or low left-side batteries at the time that I received them. I believe 3 out of the 4 have the original AMG batteries. To date I have not replaced a single one of those left-hand batteries; however, all 4 vehicles' LH batteries responded well after a long-slow smart charger charging. All 4 also had electrical glitches that cleared-up after the AMG batteries were topped off. Daily driving: My understanding is that a vehicle type battery typically requires "quite awhile" (hours) to fully charge... so a "daily driver" vehicle who's operation time vs. starts and other heavy draws while it's not running (adjustments of the seats routinely before starting for example) might routinely have a less than "fully charged" /full voltage battery.

eh?

 

I have a “ Banner “ brand AGM always on the trickle charger .Don't know the age I in my 4 th year with this car ,
How ever there is a tell tail when the V drops below a certain level if I have done a few high demand trips - short , music on , heated seats , lights etc .The pink “ seat back not locked “ symbol comes up ....no alarm just the graphics .
If we turn off the ancillaries it’s goes out ,
It obviously goes out after a long run etc ,

So my seat back module / memory / back latch etc is the first to squeal if the “ house bat “ gets low ,


Anybody else got a “ tell “


And yes before anyone asks I did inspect and replace the seat back micro switches .......before figuring it’s voltage related .

 

Yes John: The power trunk lid on our '07 GT gets irrational with a low house battery. This happens when I fart-off plugging in the maintenance charger and the car sits longer than I expected... like a week or 10 days goes by. And the "trip to town" (45 - 50 minutes drive time) doesn't seem to do the trick for charging the house battery back up to snuff enough for the power trunk lid to play nicely... it takes a "couple days" on the battery tender to get things back in the pink after a bout of a week or more unattended house battery.

 

I hoped that the drivers window shuffling up and down (car unlocked, key nearby) for no reason might be battery related... Not sure it is now.

Also had the seatback unlocked warning, but that is a hard fault I think as it only happens under braking with nobody in the passenger seat.

 

But does the window shuffle when you get in and are sitting in the driver's seat? And if so, does it continue to shuffle after starting the vehicle? Depending on the answer, I wouldn't rule-out the battery. I'd say try plugging in your battery charger when the window starts shuffling and see if it stops with the input from the charger. It could be that the house battery is snuffed (or at least is getting tired)... you might have one weak cell and the voltage of that house battery is dropping back down to 11.5v basically as-soon as you shut the engine off. I'm of the understanding a fully charged "good" battery should test-meter about 12.6v unloaded.

 

This is a good point .
As my “ tell “ disappears in about 1 min after the trickle charger is connected .
Been getting 12.6/12.7 V so my house batts edging towards the end of its useful life I think .Its not a binary thing .There's no clear indicator without a Voltage drop / load test .

So if forget to plug in the charger for a few days or as said do a few multiple short ( most accessories running ) trips the “seat back unlocked” warning symbol pops up ,Disappears once the charger is plugged in or a long run ,
Hence I figured out a Voltage issue .

With the charger in the V goes up to 13.2 on the house .

 

I haven't done too much testing on this yet... Mainly due to weather... But AFAICT the window shuffling happens only with the car off, doors shut, not locked and key nearby. It's occasional and may even happen ages after I've closed the doors.

The drivers side window drops to the 'opening door' position then goes back up again. I wondered if it thinks the door is opening when its not. Obviously the window motor is pulling current which will cane the battery.

Yesterday I put a new battery in. If the rain holds off for more than 10 mins I will do some experiments to see whats going on.

 

Still very mysterious. Sometimes the windows (drivers side) go crazy shuffling up and down. Other times not at all. VCDS is showing the window regulator values changing but not the door lock status so its not that.

Also measured the current draw on the house battery with the car unlocked and boot open, not switched on. 1A! so it's not surprising the battery gets drained without a tender...