Battery Maintainer Wiring?

[Supra Dupra]

Regarding the power wiring for the dash cams -- you have to find a switched 12V power source that shuts off when the car is off. This is required whether or not you have a camera battery pack installed. Nothing should be pulling power from the car when it's shut off, not the camera and not the battery pack.

The way it will work is that the camera always draws from the battery pack, never from the car directly. When the car is on, the battery pack is being recharged. When the car is off, nothing is drawing from the car. The camera will run as long as the battery pack lasts.

I've seen people talk about just adding the battery pack without changing the power source, and that won't help at all, eventually you will still have a problem. Also, don't use any device that purports to monitor the voltage and shut off at a preset limit, that won't help either. The camera and its battery pack need to be wired so that they are not drawing any power from the car when the car is turned off, under any circumstances.

Not all installers are hip to this, so be sure to talk it over with them and make sure they are tying into a circuit that gets cut off when the car is off. This is not hard, just requires some minor knowledge of BMW electrical systems and/or some careful testing with a voltmeter.

It looks like RRKnight's installer was aware of this and, as shown in the video above, tested for the circuits that turn off when the car is shut off (those that immediately turn off and not those that stay on for 5~20 minutes thereafter). Even then it seems to have caused issues... and as you said, the next remedy seems to be adding an external battery between the camera and the car battery, but as you've mentioned, I'm not sure how this would solve the issue because something (this time, the external battery instead of the camera) would be hooked up to the same ports and presumably cause the same issue. I've been watching a lot of YouTube videos about BMW hardwire dashcam installs and I'm still not sure how to go about doing this without tripping the error message in the Supra based on what people here have been experiencing. :-/

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[larrymz3]

My solution is: My dashcam is plugged into the USB port of the entertainment system. The USB port does not immediatedly switch off when the engine is stopped with the Start/Stop button. But, after a while (I think 2 or 3 minutes, depends on whether you lock the car or not), the USB port is currentless and the dashcam switches off.

Probably, however, it is better to return to the original topic of this thread, i.e. where to plug a battery charger.

Not knowing about issues and by default not reading manuals (because of my extreme cleverness ;-)), I already plugged my battery charger into the 12V port in the trunk on the first day after delivery. The battery was charged over night and I had no electric damage or error message. Probably, the electric system of the car has respect for my cleverness. I assume, however, I was simply a lucky man. The car was locked over night.

Since the battery charger (of CTEK) also has a battery maintaining function, I can image, that battery maintaining over a longer period works as well. CTEK offers a 12V plug adapter.

Where is the 12v outlet in the trunk? I must have missed it.

 

[s219]

It looks like RRKnight's installer was aware of this and, as shown in the video above, tested for the circuits that turn off when the car is shut off (those that immediately turn off and not those that stay on for 5~20 minutes thereafter).

RRKnight said that wasn't his car in the video, and other details he posted make it sound like his camera was wired to a constant 12V source (use of voltage sensing relay, etc -- that wouldn't even work on a circuit that shuts off when the car is off since there would be nothing to sense -- so that tells me the installer ran it to constant 12V). Nothing else would explain the problems he had.

This has all been hashed out over and over on BMW forums so I would make sure the installer does it exactly the right way and not try to "relearn" everything for the Supra. Find a switched 12V circuit that cuts off when the car is shut off and use that.

 

[Supra Dupra]

Yeah, I know it wasn’t his car but that was his installer so I’m surprised that they’d install it differently for two of the same car knowing that they’re using BMW batteries. In any event, I guess I just need to find a shop that specializes in BMW installs and take the Supra there.

 

[Supriast]

Where is the 12v outlet in the trunk? I must have missed it.

European version, right panel of trunk below the light

 

[larrymz3]

European version, right panel of trunk below the light

I will double check when I get home but I’m fairly certain my US car doesn’t have this.

 

[Natek]

Just purchased a new Ctek Multi US 7002 and was wondering where the best place to wire it would be?

Can it be wired under the the hood? Or would it have to wired directly to trunk in battery?

Any luck with this?

I suspect the place to hook up the connection (not the alligator clips persay, you probably could connect the bolt down pigtail) would be the following but someone should double check me:

The T50 bolt looks to be 14 ft-lbs of torque to attach, I tried to loosen mine but was afraid I was going to break something.

If you manage to get this working please let me know- I have the same ctek charger but haven't spent a lot of time with it yet. Winter is coming though.

 

[larrymz3]

Any luck with this?

I suspect the place to hook up the connection (not the alligator clips persay, you probably could connect the bolt down pigtail) would be the following but someone should double check me:

The T50 bolt looks to be 14 ft-lbs of torque to attach, I tried to loosen mine but was afraid I was going to break something.

If you manage to get this working please let me know- I have the same ctek charger but haven't spent a lot of time with it yet. Winter is coming though.

Yep, this is where my mechanic wired mine to. The three posts under the plastic cover are connected via a bus bar so you can connect the positive to any of the three bolts. Mine is on the second. Works great.

 

[POS VETT]

On my C6 Z06 (battery located in the right rear corner), I ran a modified Battery Tender pigtail through one of weather-resistant passages in the rear trunk wall and routed it to one of the openings above the rear license plate. I drilled a small hole in the top right corner of the license plate cover and, using a small black zip tie, the connector is secured. It's inconspicuous enough and practical (no need to open the hatch to connect).

I have not investigated whether a similar principle could be applied to the Supra, but I imagine it's a possibility. I prefer connecting a float charger directly to the battery instead of going through the car wiring. Just a thought.

 

[s219]

I agree that connecting a maintainer directly to the battery is preferable, especially when the battery can be isolated from its loads. On my boat, the shore charger is wired directly to the batteries and a battery switch isolates the batteries from their respective circuits.

On a car where you don't normally isolate the battery, I don't think it matters how it's wired but I would still prefer going directly to the battery just to minimize the path that juice follows from the maintainer to the battery. I also feel like this means you should only use a high quality charger that won't put dirty power into the car's electrical system. On boats, there is a big difference between a basic $50 maintainer and the $200+ smart maintainers. Makes me wonder if any of that translates to cars.

 

[A90 Zero]

Did anybody confirm that the 12 volt outlet plug inside the car is switched, so it would not work to attach the battery maintainer to this outlet?

 

[larrymz3]

I agree that connecting a maintainer directly to the battery is preferable, especially when the battery can be isolated from its loads. On my boat, the shore charger is wired directly to the batteries and a battery switch isolates the batteries from their respective circuits.

On a car where you don't normally isolate the battery, I don't think it matters how it's wired but I would still prefer going directly to the battery just to minimize the path that juice follows from the maintainer to the battery. I also feel like this means you should only use a high quality charger that won't put dirty power into the car's electrical system. On boats, there is a big difference between a basic $50 maintainer and the $200+ smart maintainers. Makes me wonder if any of that translates to cars.

I agree - every vehicle I've owned the maintainer has been wired directly to the battery... however... if you read the BMW forums there are a TON of posts specifically warning against doing this on BMW's with BMS systems (of which the B58/Supra has). Lots of anecdotal stories about issues arising from direct wiring - everything from frying ECU/DME to various other electrical issues. The consensus on BMW is to wire maintainers to the charging posts... Even BMW says so officially with their official BMW (Ctek) battery charger.

I didn't want to take a chance... so, I had mine wired to the bus bar under the hood which is the factory approved charging/jump post.

 

[Natek]

i wired mine in the engine bay too.... in line with how the ctek rebranded bmw charger is recommended. I intend to drop the wires out the bottom and plug it in (note i store on a lift). I plugged it in yesterday and the car didnt blow up.

 

[A90 Zero]

Since the BMS is attached directly to the negative battery terminal, is it safe to connect the battery tender to the positive battery terminal and some good ground location in the trunk? That way you would not be bypassing the BMS.

 

[larrymz3]

Since the BMS is attached directly to the negative battery terminal, is it safe to connect the battery tender to the positive battery terminal and some good ground location in the trunk? That way you would not be bypassing the BMS.

You've seen multiple posts from folks all saying to wire it under the hood the way BMW recommends... I guess if you feel you are more knowledgable then the manufacturer then go for it.

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