If you replace the batteries, ensure you get the best that money can buy. These cars are HARD on mediocre or bargain batteries. Be prepared to spend serious money. In Canada, both batteries were about $900.00.

 

Peter, I recently replaced both batteries with properly rated and sized Interstates. Do you consider them to be the best money can buy. The originals were VARTAs apparently from Germany and seemingly not available in the US. I paid about $550 USD including about $100 for installation. The Bentley dealer quote was about $1000 USD and said labor was 2.5 hours. My indie shop removed and installed in less than 1 hour. I watched him do it and the main battery was HEAVY and not easy to handle in and out.

 

As you say, this is not a trivial exercise. Good luck with the Interstates. I am assuming you noted that the two batteries are different types with the house battery being the expensive one. Please let us know if you experience any issues with your new batteries. If you car sits for more than a week at a time, you may wish to consider leaving a trickle charger plugged in. I've had good luck with CTEK.

 

Peter, thanks for your response. I've had the Interstates for about 9 months and they seem perfect -- strong start and no codes thrown. My intent was to buy the best I could for peace of mind. Do you know of higher quality ones of the correct size?
I use a CTEK 7002 maintainer which is higher AMP rated than the CTEK 3000 which I had but it never charged completely. A CTEK engineer said it was not strong enough for that huge house battery

 

My response regarding your choice of batteries was not intended to denigrate Interstate in any way. Their top of the line product is first rate. I am not qualified regarding price as product pricing in Canada was/is significantly higher than in the US. I went OEM as the VARTA product was available in Canada at the time of replacement (almost five years ago).

I have used the lower-rated CTEK 3000 with good results (i.e. fully charged). However, I may be deceiving myself as I certainly would trust the recommendation of a CTEK engineer suggesting a 7002.