Disconnecting the Battery in an Aston Martin DB9

Battery Compartment Opened on an Aston Martin DB9
Battery Negative Terminal Disconnected

There are MANY service events for your DB9 that say to disconnect the battery as one of the steps.   I am as realistic as anyone in this regard – meaning I usually skip this step if I think I can get away with it.  The safety Nazi’s probably tell you disconnect the battery to vacuum the carpets.   But, there are certainly some circumstances where this should be followed.  Working on your fuel system, working on the electrical system, etc.  Any situation where an accidental spark or short could destroy parts of the car.The DB9 has a bunch of computer modules, and sadly they have ‘memories’ that require the battery to ALWAYS be present (more modern cars have memories that remain even if the power is removed).   If the battery power is interrupted for even a short period of time, they dump their stored memory parameters, and you have to set things up again.  Simple things like the clock and stereo presets, a few more challenging items like the window auto drop and seat calibrations, plus the more difficult misfire correction factors that must be relearned.   I’ve done blog posts on each of those already so I hope those help.

Aston Martin released Service Bulletin SB153 in December 2004 about each of the modules in the car that need reprogramming after losing power for any reason.  You can read SB153 here.

Location of Battery in an Aston Martin DB9To be clear, I am talking about actually disconnecting the ground lead on the actual battery – cutting off all power to the car.   I am NOT talking about the battery disconnect button in the trunk (boot) that you could use when storing the vehicle.

The battery is located under the right hand rear seat.  Yep, it’s gonna be fun reaching this.  Limber up at Yoga class.

Tools Required

Craftsman 8mm 6-point socketYou don’t need many tools at all:

  • 8mm 6-point socket with a simple nut driver to speed up the removal (the screws are plentiful and long)
  • 8mm box end wrench (for the hard to reach spots)
  • 13mm box end wrench to disconnect the negative terminal battery cable

Procedure

The process won’t take long.  You’ll be done in under 10 minutes.

  • Start by moving the right hand seat all the way forward, and then tip the back all the way forward as well to give you as much access as possible to the rear seat area.   Note:  Keep in mind once you’ve disconnected the battery you won’t be able to move the seat again until its reconnected, so if you are servicing something under the dash on the same side, this presents a bit of a conundrum.
  • Right Rear Seat Base of an Aston Martin DB9You’ll need to remove the leather seat squab next.   Freaky as this sounds, its very easy.   The seat is only held in place with 2 patches of Velcro.   Just grip the front lower lip of the seat and lift up.  You should hear the ‘rrrrippppp’ of the Velcro and just remove the seat base and put it someplace safe.   See my video below to watch exactly how it comes out.
  • Right Rear Seat Lower Back of an Aston Martin DB9Next you need to remove the lower panel of the seat back.  Its a small simple piece, also held in place by four small pads of Velcro.  Just grip it carefully and pull it out straight forward.  Put it someplace safe.
  • Now you have access to the aluminum panel that is the seat base and the battery cover.   Aston Martin really didn’t want it to fall out, so it’s held in place by ten (10) 8mm bolts.  Just remove all the bolts.
  • Battery Compartment Cover in an Aston Martin DB9Lift the battery cover out, being careful not to bang it around against the electrical connections or the leather.  Best to remove it without touching anything else.
  • With the battery now exposed you can see the positive battery terminal on the left (under plastic covers) and the negative battery terminal exposed on the right.
  • See my Note below on the Alarm system, and it’s suggestion that you complete the next two steps (loosening and disconnecting the negative battery cable) within 10 seconds of switching off the ignition.
  • Negative Battery Terminal Disconnected on an Aston Martin DB9Using the 13 mm box end wrench, loosen the battery terminal nut about 1 turn, just enough to break the ‘clamp’ it has on the battery post.
  • Wiggle the terminal loose by twisting it slightly on the post, and once loosened just lift it away from the post.
  • Position the battery cable away from the negative terminal so it won’t accidentally move back and accidentally touch the negative battery post.

That’s it for disconnecting the battery.  In another post I will cover connecting it again and the steps necessary to fix all the things that just lost their computer memories.

Here is a short video on the process.


 

A Warning about the Car Alarm

Battery System Section 14.01 in Aston Martin DB9 Workshop Manual CoverIn the official Aston Martin Workshop manual section about the battery system, it has a warning that the cars alarm system will be set off if the battery is disconnected more than 10 seconds after the key is turned off.  Specifically:

“The vehicle is installed with an alarm which will be activated if the battery is disconnected. This alarm is driven by a back up battery within the alarm sounder unit. To prevent the alarm from sounding when the battery is disconnected (for workshop procedures), disconnect the battery within 10 seconds of switching off the ignition.”

When I disconnected my battery it was at least 30 minutes after switching off the ignition, and no alarm sounded.   Perhaps my car doesn’t have this feature, or the referenced back up battery is shot and can’t hold a charge either.   Anyways, you might want to factor this into your process.

2 thoughts on “Disconnecting the Battery in an Aston Martin DB9

  1. Eric Rothenberg

    Steve,
    Thank you so much for your videos. A fantastic job!
    I have a 2005 DB9 here in Houston,Texas. The dealer replaced my battery a couple of years ago for well over $500. Car is not a daily driver. Dealer said to keep a trickle charger on it so it wouldn’t go dead. Well, I guessed it worked for awhile but now even with the trickle charger indicating a full charge, the car needed to be jumped. After watching your videos I went and bought a new Bosch battery and will attempt to change it tomorrow.
    My first question is if I leave the trickle charger attached during the change, will I still have to reset all the modules with a memory?
    Second, since the trickle charger is indicating a full charge, could it be something else besides a weak battery?
    Thanks again,
    Eric

    Like

    1. Hi Eric. Thanks for the kudos! Sorry to hear about the battery. If you’ve read my battery article, I mentioned that the Odyssey smart battery chargers combined with an AGM battery should give you great service, even in trickle mode. They deep cycle the battery to keep it conditioned. If your old battery was a lead acid traditional type, a plain trickle charge could lead to sulfating and poor battery performance even when charged. If the replacement battery starts it effortlessly, I wouldn’t look much farther.

      Will a trickle charger keep the car ‘alive’ when doing the replacement? Probably, but then the ‘risk’ is back that the cables you seem me flopping around while doing the swap will have power from another source, and you are back to having a possibility of shorting something expensive out. If you are super careful and take this into consideration, sure, could save the hassle of relearning the misfire correction factors. The other items just take about 5 mins to fix.

      Good luck!

      Like

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