LV Battery grounding question for audio upgrade

[MrLoganRoss]

I need to have a better ground for a higher end audio system being installed in the truck. My understanding is that the ground points in the truck cabin back wall should not be used because the cabin is aluminum. Yet Ford grounds there. Doesn’t that mean they run a ground elsewhere?

nevertheless, I have two 4 gauge grounds that need to be run. Due to the BMS, where should they be run? Not the battery right? How about the negative post on the passenger side of the Frunk?

thanks!

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[Heliian]

because the cabin is aluminum.

The internet is a modern wonder of ridiculousness sometimes. Vehicles and airplanes have been made from aluminium for decades, it's a good conductor.

Personally, I'd just run it to the battery negative or somewhere near the post. Keep it away from the orange wires.

 

[Maquis]

Aluminum is a better conductor than steel.

 

[Duke_239]

The wires that bring the electricity to your house are made of Aluminum.

 

[MrLoganRoss]

Thanks. I thought the issue wasn’t the aluminum you would attach to but the limited interface between that and the chassis. I thought the issue was also that the current ground wire was not big enough to support the current from two 4awg?

I really appreciate the ongoing help (and pictures if they exist).

also, it sounds like I am correct that you should not run the ground directly to the battery terminal since it messes with the BMS and any ground should be outside the OEM battery terminal/BMS to the battery?

Chris

 

[bmwhitetx]

Thanks. I thought the issue wasn’t the aluminum you would attach to but the limited interface between that and the chassis. I thought the issue was also that the current ground wire was not big enough to support the current from two 4awg?

I really appreciate the ongoing help (and pictures if they exist).

also, it sounds like I am correct that you should not run the ground directly to the battery terminal since it messes with the BMS and any ground should be outside the OEM battery terminal/BMS to the battery?

Chris

You can run to the battery area but you need to be downstream of the BMS module which is attached to the negative terminal. Here is a pic I posted many years ago. You can connect to the blue circles, not the red X. The studs on the BMS will take a 6mm nut.

 

[RLXXI]

Open the frunk and pull off the left side panel over the washer fluid bottle and you'll see where Ford wants you to connect to ground for jump starting which is an excellent place to ground it. Do NOT connect directly to the battery as you'll throw off the BMS for the LVB.

 

[MrLoganRoss]

Ok RLL and BMW, could you help me reconcile your two recommendations?

 

[K6CCC]

With your sound system upgrade, how much DC power are you going to drawing at peak, and how are you planning on supplying that power?

 

[MrLoganRoss]

Max power rms for all three components is 1900 (have no expectations to hit this). I am not interested in SPL so actual should be around 1100

 

[K6CCC]

Max power rms for all three components is 1900 (have no expectations to hit this). I am not interested in SPL so actual should be around 1100

I assume you mean in watts, so again assuming you taking that off the 12 volt battery, that will come up to almost 100 amps. Off hand, I can see that being an issue with trying to draw that much power on a somewhat ongoing basis from the little 12 volt LVB. Or as you planning on some other way of getting power to the new system?

Just as an FYI, I will have a bunch of 2-way radios in my truck along with some off-road lighting. That will be powered from a completely separate 12 volt system with two deep cycle batteries in the bed. That system will be charged from two battery chargers that will come from the 120 V AC inverters. Not going to touch the vehicle 12 volt system at all.

 

[MrLoganRoss]

Super helpful. I am assuming I can use car scanner to monitor? This is is a hat is shows when playing music the way I listen to it.

 

[MrLoganRoss]

Not sure if this reading right. This is what I see. One with the car off. The other with car on and my music playing at my listening levels.

if the issue is the battery will die on 2 years instead of 3, I am all with that.
I am just having a hard time figuring out how to monitor.

 

[bmwhitetx]

Ok RLL and BMW, could you help me reconcile your two recommendations?

We are both saying not to connect directly to the negative battery terminal. Electrically speaking the point I show and the jump spot under the left panel are equivalent.

You will want a tight connection - I don't recall if the jump point has a nut/bolt you can connect to.

The Police Modifier Bulletin also suggests a spot that is above and to the right of the battery.

 

[MrLoganRoss]

Super helpful. Let me study this. I am pretty sure I don’t have an all overdraw issue but I am open to better option than car scanner to measure.

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