I recently replaced the battery in my R53 and considering I don't drive the car nearly as often as I'd like and that there seems to be an ever so slight drain, I'd like to install a cut off switch to get the most life out of the new battery. The question is where to install... I ordered a switch that clamps on to the battery post that allows for the lead to clamp on. No cutting or splicing, super simple and what would seemingly be effective. The problem is, with the boot latch being electric it's not going to be so easy to switch it back on. I realized this immediately after I closed the hatch while securing the car prior to leaving it...duh.
Hoping someone can offer some advice as to where the best spot to install this would be. I'd like to be able to cut the power, secure the car and then be able to switch it back on with out having to hop back and fold down the rear bench or hook up a booster to front port to unlock the boot. Ideally somewhere in the front of the car under the hood? Is this possible? Thanks in advance.

 

I think I know what cutoff switch you have...and not sure it would be an easy add-on...but the first place to look, would somewhat obviously be in / on the little black box where the accident cutoff switch is, next to the air filter box. This is...where the the battery cable ties into the rest of the electrical system.

Or...do what I did on an older car that I used to own. I cut the battery cable (the battery was moved to the trunk) as it passed the front seats. I drilled a hole in the floor and put the control part of the switch on the interior of the floor, and continued the cable to the starter.
Doing this also made it into a "safety", or "anti-theft" switch, being that the switch handle was not in an obvious place.

Mike

 

Thanks for the reply Mike. I have the switch below. Very straight forward. Not exactly married to this particular one but would prefer to keep this as simple as possible as much as I like the idea of having it somewhere in the inside of the car.

I thought the accident cut off was the little black box on the pos lead off the battery, in the back of the car?

 

I have the same switch on my R53 although I haven’t used it for a few years since the car is now on a battery tender.

Have you checked to see if your car has the hatch release cable under the rear seat cushion? Somewhere around 2003 they added one in front of the seat belt buckles. Once you get used to where it is, you should be able to just slide your hand under without pulling up the cushion.

 

I haven’t checked. In fact I didn’t even know there was one!…it’s a 2005 so hopefully it’s there. Thank you!

 

A 2005 should definitely have one. A few things to look out for when cutting or losing power:

• You might need to push on the hatch from the inside, or have another person open the hatch, while pulling the release cable if the latch or seals are sticky.
• Make sure the window is not completely up when closing the door without power or it will hit the roof trim and possibly damage the trim, window, or tint. It will open, but obviously not dip to close or rise to seal. Since my car was inside I would open both doors before cutting power to keep the windows in the dipped position.
• This function probably needs to be reset for each window when power is re-connected. Open the window fully and continue holding the switch down for about 5 seconds, then close the window and continue holding for another 5 seconds. This should also reset the one touch down function.

It’s been a while since I’ve cut power from the battery so I don’t remember all of the things that need to be reset, or get reset like possibly the trip meter and clock, but I was getting concerned on seeing posts where the ECU or immobilizer had some kind of problem after sitting un-powered and needed to be replaced or sent out for repair so I decided to start using battery maintainer instead. The connector is hooked up to the jumper/charging post in the engine compartment

 

Thank you for this. In the past with no power I've typically closed the doors pushing from the top of the window. Will check on resetting auto up down when I power her back up. Likely not for another few weeks at this point. Has been sitting for 3 with no power at all now...

Honestly, you've got me a little concerned in RE: The ECU & immobilizer. A tender as of right now is not possible for me unfortunately. I did a brief search, can you reference any threads here on ECU or immobilizer issues after being unpowered?

 

I don’t have any links, and the posts didn’t specifically say the cause of the issue was a dead or disconnected battery but when describing the problem, they often included there were no starting issues before their battery went dead or was disconnected while in storage and the fix was sending out the EWS to be reset.

This issue is rare, and I’m sure they’re people who say you can also damage some module hooking up a tender, so I guess it just comes down to personal preference on storage methods.

 

The car does, in fact, have the boot pull release. Thank you for the heads up there.

Seems I will likely need to replace the neg terminal lead, find a different switch or different location to install though. The lead is not quite long enough to position the switch where it would need to be for the floor cover to sit properly.

Power has been cut for over a month now and aside from the clock being off, everything else seems fine.

 

I just ditched one of those off my 05. I don’t recommend it unless you are gonna leave it over winter etc unplugged, and if so, why not just take the neg terminal off the car side with a 10mm? Just go start the car every week or couple of weeks and run it for a few minutes till it warms up.