Eventually you have to service the battery in your DB9. They just don’t last forever – and the typical lifespan of a traditional flooded lead acid battery (like the ones originally fitted) is about 5 years. The good news is that when the time comes to replace your battery you’ll be well equipped to know how and avoid a potentially costly trip to the dealership.
If you are wondering about what battery to get I’ve already completed a detailed article you should check out – Replacement Battery Options for an Aston Martin DB9. You’ll see how I gravitated to purchasing a Bosch 49-850BAGM Absorbed Glass Matt (AGM) battery. Now I’ll share the details of how to install it.
You will only need a few simple tools:
- 8 mm socket
- 8 mm wrench
- 13 mm socket
- 13 mm wrench
- Ratchet for sockets
- Nut driver for sockets
- Torque wrench (suitable for 9 Nm or 7 ft lbs)
- 4 mm Allen wrench
- 12″ of stiff wire like bailing wire, pipe cleaner, coat hanger, etc.
- Micro fiber towels to protect center console, carpets, etc.
You should be able to tackle this easily in under an hour, probably 30 minutes if things go well.
The first steps of accessing the battery compartment and removing the battery cover are well described in my other article and video – Disconnecting the Battery in an Aston Martin DB9. You need the 8mm socket and wrench in that article. Please follow those steps entirely and then carry on with the steps below.
- Use the 13 mm wrench and loosen the top nut on the Negative battery terminal. Wiggle the terminal loose and lift up and away.
- Note: It’s important to do the Negative terminal first to reduce the risk of an accidental short with your tools. If you did the positive terminal first and accidentally touched the wrench to the battery box and positive terminal, you’d have a 900 amp arc welder and likely do very serious damage to the car (like setting it on fire). By disconnecting the negative first, the car is no longer grounded and the risk is removed.
- Use the 13 mm wrench and loosen the top nut on the Positive battery terminal. Wiggle the terminal loose and lift up and away.
- Dismount the electrical octopus from the top of the battery mount by:
- Using your fingers, gently pryse and lift the black plastic safety cover off the assembly. It’s held in place by 3 plastic press in snaps. Check out the video below to see what I mean.
- Use your 4 mm Allen wrench and remove the three bolts that mount the electric bracket to the battery bracket. They are right on top.
- On my car, there was one grey cable that had an electrical connector that was mounted to the battery bracket, but hidden under the octopus on the left side. You can see the black plastic teet from the connector protruding through the mounting hole. Using your pliers, squeeze the teet so that you can ease it back though the mounting hole and dismount the electrical connector. It’s easier than it sounds.
- You should now be able to lift the electrical octopus up and rotate it towards the back of the car to get clear access to the battery bracket and its bolts.
- Remove the battery bracket by:
- Use your 8mm socket and ratchet/nut driver to remove the two 8mm bolts holding the battery bracket down. There is one bolt on either side of the bracket.
- Grab and wiggle the bracket straight up. On my car this was difficult. The bracket slides along a track, and it’s not designed well. Just be patient and wiggle it up and out.
- Lift the battery out by:
- Keep in mind the battery weighs about 53 lbs (24 kgs), and you are leaning in from the doorway with poor access. This is a PITA.
- There is still a vent tube connected to the battery on the door side. There is little access to it, but you should be able to see it. If you can partially lift the battery (just tipping it to get your fingers in) you might try and disconnect the vent tube and leave in place. Me, I went gung ho and pulled it out with the battery.
- Lift the battery up and out of the battery compartment. You should be able to just rest it on the lip of the battery compartment to get a rest.
- Disconnect the vent tube from the battery if you haven’t already.
- Lift the battery up and the rest of the way out of the car (watch your back!)
- Remember to take your old battery to a proper battery recycler to dispose of it. It is hazardous waste and shouldn’t end up in a landfill. My local Pepboys (where I purchased my replacement battery) took the old battery back to recycle.
- Prepare the vent tube to be reconnected
So I ran into a little challenge here. The vent tube is designed to connect to the top of the battery, go through a hole in the bottom of the battery compartment, and then through a 2-3 inch space before it goes through a small hole in a rubber grommet in the bottom of the car. The original vent tube was trimmed to length after install at the factory. Since I pulled it out during the removal, how exactly can I get it connected to the battery, through the hole, and down and through the grommet while I have zero access to it?
What I did was take a 12 inch piece of bendy wire and stick it in the end of the existing hose, essentially extending the hose length for the purpose of the fitment. Afterwards, I will just pull the wire out the bottom of the car.
- I put some gentle wavy kinks in the wire so it stuck itself into the hose better and wouldn’t fall out.
Place the vent tube into position in the battery compartment, fishing the bottom through the hole and down and out of the grommet beneath the car. Even if you didn’t fully remove the vent tube, you might have tugged it out of the grommet and its no longer exiting the bottom of the car, but rather in the gap between the battery box and car floor. Check out the video so see what I mean.
- Place the new replacement battery in the car:
- The replacement also weighs 52 lbs (24 kgs) , so watch your back and be careful of banging up your leather upholstery
- Lift the battery through the door opening and rest it on the battery compartment lip just as we did while removing it. This will give you time to reposition your body to lower it the rest of the way.
- Lower the battery into the compartment. Keep the vent tube out of the way to the side.
- Once at the bottom, tip the battery over a bit to be able to get your fingers into the gap and connect the vent tube to the vent port on the top of the battery. See my video below on how I did it. Remove the alignment wire out of the tube underneath the car.
- With the vent tube connected make sure the battery is seated flat on the bottom of the compartment (wiggle it around to be sure) and skooch the battery as far forward as possible so the bottom beveled portion of the battery frame wedged under the mount in the compartment.
- Replace the battery bracket by:
- Align the edges of the bracket over the slots, and start to lower the bracket.
- This doesn’t slide smoothly, and you will need to wiggle it down (a.k.a. bang on it with your fist) and keep it going down level on both sides.
- As it bottoms out, wiggle the battery to make sure the bracket and battery are mating up and wedging the battery into place.
- NOTE: I didn’t realize when I was removing the bracket it actually doesn’t sit flush on the surface of the compartment. By design there will be some amount of space beneath the bracket under the bolts. The bracket is a ‘wedge style’ so you don’t actually want it to bottom out.
- Install the battery bracket bolts by:
- Replace the two 8 mm battery bracket hold down bolts.
- Use your 8mm socket and ratchet to tighten down the bolts. I couldn’t find a torque spec, and I would just suggest ‘Snug’. Don’t over tighten since you could bend the bracket flanges over since they don’t sit flush on the compartment underneath.
- Try and move the battery around. It should be unmovable at this point, solidly mounted to the car. If it moves at all, stop and work out why the bracket doesn’t have it pinned in place.
- Remount the electrical octopus
- Lower the electrical octopus loosely into place
- Align the grey cable’s electrical connector and push the plastic teet though the hole in the mounting bracket until it click solidly into place.
- Ensure the grey cable is seated in its slot (see the video)
- Loosely start the three 4 mm screws to mount the bracket and snug them up using the Allen wrench.
- Reinstall the black plastic safety cover by aligning and pressing the three snaps into place.
- Reconnect the positive battery terminal by:
- Remove the disposable plastic safety cover from the battery post if so equipped.
- I applied some Permatex Battery Protector (grease) to the battery post to aide in corrosion protection and lubrication
- Wiggle the positive battery cable down over the post making sure its fully seated.
- Using the 13 mm wrench tighten the battery terminal.
- Set your Torque wrench to 9 Nm (7 ft lbs) as published by Aston Martin in the official workshop manual.
- Use the 13 mm socket to Torque the nut to spec.
- Lower the red rubber safety shroud around the terminal to protect it.
- Reconnect the negative battery terminal by:
- Follow the same procedure as the positive terminal.
- Note: I had to loosen my terminal a bit to get it to fit over the new battery post, I guess the new battery’s post was slightly larger in diameter. I had to use a hammer and tap the terminal down over the post.
- Note: You will start to hear your car come to life as soon as the negative cable touches the post. The CD Changer will index, and you may hear some clicking for a few moments around the car. Not to worry.
The final steps will be to replace the battery cover and seat squab, well described in my other article and video – Reconnecting the Battery in an Aston Martin DB9. Follow those steps to complete the project.
That article also ends with reminding you about the five steps you need to do anytime you’ve disconnected the battery as defined by Aston Martin Service Bulletin SB153. Namely:
Reset the Window Autodrop Calibration – your windows automatically open a tiny amount as you open your door handle, and this will be forgotten by the Door Modules until you recalibrate them. Check out the article here.
Reset your Seat Calibration – your power seats need to learn the extent of their adjustment ranges (up/down and front/back), and this will be forgotten by the Seat Modules until you recalibrate them. Sure symptom they are forgotten is you can’t move your seat any direction but forward. Check out the article here.
Reset your Clock – the beautiful clock in the dash will need to be properly set to the current time again. Check out the article here.
Reset your Radio Presets – I don’t have a video on this, but all the memorized radio channels on buttons 1, 2, 3, etc. will be forgotten. Good luck remembering them all. Simple to reset, but I don’t have a video on this yet.
Relearn the Engine Misfire Correction Factors – this is the biggest PITA to redo, but also the most essential since your engine will be running in a ‘default guess’ mode until completed. The Powertrain Control Modules (PCMs) that monitor and continually adjust the engine to prevent misfires needs to calibrate itself following a specific coast down procedure that has to be done at highway speeds. Check out the article here.
OK, here is my video showing the process above. My apologies in advance that it’s about 20 minutes long but I wanted to make sure I showed all the steps so you’d be successful in your project.
And here is the video on Disconnecting the Battery that shows you how to access it behind the rear seat and remove the cover.
And here is the video on Reconnecting the Battery that shows you how to replace the battery cover and replace the seat.