Electrical help...I need to tap into battery voltage

Gray_Panther · 03-16-2013, 06:08 PM

Hey all,

Soon I am starting on a headlight retrofit on my 128i's halogen headlights. I would usually tap power from the battery, but BMW puts our batteries in the rear instead of the front. Is there a place on the front of the car that is connected to the positive terminal of the battery to supply constant 12VDC?

I need this question answered but in the meantime here is a little teaser

NorthernDancer · 03-16-2013, 06:22 PM

the battery booster post under the hood.

Gray_Panther · 03-16-2013, 07:22 PM

Quote:

Originally Posted by NoirthernDancer

the battery booster post under the hood.

Gratitude for replying to my question.

Where exactly is the battery booster post? Hopefully it is easy to spot or labeled in some way.

b1aze · 03-16-2013, 07:45 PM

Quote:

Originally Posted by NoirthernDancer

the battery booster post under the hood.

That should really be used to jump a car only, right? Not as a permanent source for 12VDC power from the battery? It's not powered on and off by the key is it? You really need a switched 12vdc source.

Gray_Panther · 03-16-2013, 08:03 PM

If it is powered on/off by the key, then that should suffice since the circuit closes when the key is inserted. I can look into that as soon as I find where the post is. Can anyone point me to it?
Any other places I can tap off of?

tuco44 · 03-16-2013, 10:29 PM

Quote:

Originally Posted by Gray_Panther

If it is powered on/off by the key, then that should suffice since the circuit closes when the key is inserted. I can look into that as soon as I find where the post is. Can anyone point me to it?
Any other places I can tap off of?

Try the Owner's Manual, it is shown in there...........

Bmwbreed · 03-17-2013, 04:11 AM

It's on the right side (passenger) side if engine bay toward the firewall. It's covered by a red plastic piece that slips on and off. There are 2 bolts right under it connected to the post. I unscrewed one of those and put a wire under it and used it for my alpine angel eyes power supply (its what they specified to use in the DIY install as the regular halogen plugs don't provide enough voltage for hid angel eyes). I've had no battery draining issues. Even if the power supply is not interrupted with removal of the key it still shouldn't be an issue unless you left the lights on and as long as you don't alter the factory light wiring they should always still shut off automatically. My angel eyes do. Ill snap a pic for you where I tapped the pwr supply for them

Bmwbreed · 03-17-2013, 04:34 AM

See where it is relative to the engine bay. Unclip the washer fluid filler neck and there's a black plastic piece over the bolt in the next pic. Just pop it off with your finger and bam there's your power supply. That small red wire you see is the one I have running to it for my hid angel eyes. The lights will act as the remote switch to shut them on and off. Just like when hooking up a stereo amp to a battery. You use a separate remote wire to turn it on and off. The light switch should act as that.

Gray_Panther · 03-17-2013, 11:25 AM

Quote:

Originally Posted by Bmwbreed

See where it is relative to the engine bay. Unclip the washer fluid filler neck and there's a black plastic piece over the bolt in the next pic. Just pop it off with your finger and bam there's your power supply. That small red wire you see is the one I have running to it for my hid angel eyes. The lights will act as the remote switch to shut them on and off. Just like when hooking up a stereo amp to a battery. You use a separate remote wire to turn it on and off. The light switch should act as that.

THANK YOU SO MUCH!!!!

of relief

03-16-2013, 06:08 PM	#1
Gray_Panther Brigadier General 1555 Rep 3,234 Posts Drives: 128i Join Date: Jun 2012 Location: Upstate NY iTrader: (0)	Electrical help...I need to tap into battery voltage Hey all, Soon I am starting on a headlight retrofit on my 128i's halogen headlights. I would usually tap power from the battery, but BMW puts our batteries in the rear instead of the front. Is there a place on the front of the car that is connected to the positive terminal of the battery to supply constant 12VDC? I need this question answered but in the meantime here is a little teaser __________________ 2012 BMW 128i 6MT Deep Sea Blue Metallic
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03-16-2013, 06:22 PM	#2
NorthernDancer Colonel 850 Rep 2,276 Posts Drives: 08 Sedona 128 & 06 330xiT 6MT Join Date: Apr 2011 Location: Ottawa On Canada iTrader: (3)	Hello the battery booster post under the hood.
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03-16-2013, 08:03 PM	#5
Gray_Panther Brigadier General 1555 Rep 3,234 Posts Drives: 128i Join Date: Jun 2012 Location: Upstate NY iTrader: (0)	If it is powered on/off by the key, then that should suffice since the circuit closes when the key is inserted. I can look into that as soon as I find where the post is. Can anyone point me to it? Any other places I can tap off of? __________________ 2012 BMW 128i 6MT Deep Sea Blue Metallic
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03-17-2013, 04:11 AM	#7
Bmwbreed Major 60 Rep 1,198 Posts Drives: 2013 BMW 135i Join Date: Jul 2012 Location: Rota Spain (US Forces) iTrader: (3)	It's on the right side (passenger) side if engine bay toward the firewall. It's covered by a red plastic piece that slips on and off. There are 2 bolts right under it connected to the post. I unscrewed one of those and put a wire under it and used it for my alpine angel eyes power supply (its what they specified to use in the DIY install as the regular halogen plugs don't provide enough voltage for hid angel eyes). I've had no battery draining issues. Even if the power supply is not interrupted with removal of the key it still shouldn't be an issue unless you left the lights on and as long as you don't alter the factory light wiring they should always still shut off automatically. My angel eyes do. Ill snap a pic for you where I tapped the pwr supply for them Last edited by Bmwbreed; 03-17-2013 at 05:48 AM..
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03-17-2013, 04:34 AM	#8
Bmwbreed Major 60 Rep 1,198 Posts Drives: 2013 BMW 135i Join Date: Jul 2012 Location: Rota Spain (US Forces) iTrader: (3)	See where it is relative to the engine bay. Unclip the washer fluid filler neck and there's a black plastic piece over the bolt in the next pic. Just pop it off with your finger and bam there's your power supply. That small red wire you see is the one I have running to it for my hid angel eyes. The lights will act as the remote switch to shut them on and off. Just like when hooking up a stereo amp to a battery. You use a separate remote wire to turn it on and off. The light switch should act as that.
	Appreciate 0 Quote