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3.6tdv8 10 MY 2nd battery fitting?


JST

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Hello,

i am looking to fit a 2nd battery in the boot and have read the various threads on here about it.

What i would like to do is use a VSR as referenced here: http://www.fullfatrr.com/forum/topic19898.html?highlight=second+battery+fitting by Barracuda186.

i would like the vehicle ECUs to run off the aux battery (connected via VSR) rather than the main battery so if they flatten the aux battery the main battery will still have charge which could be used via a switch to power the ECU (bypassing the VSR) B186s post is exactly what i am trying to achieve.

The issue i believe i have is with some differences with the 10MY setup.

I have four cables to the +ve terminal.

one off the bottom of the pyro to the s/m i believe
one (a) that goes to the negative terminal via a plug
one (b) that goes to the rear fuse box (where the 2nd battery is installed (with fuse))
one © that if it doesnt have 12v on it the computers dont come on.

i had hoped to put a + b + c together on one side of the VSR, which i thought would mean with the 12v aux battery connected to the rear fuse box would utilise cable 'b' and feed the power to cable 'c' for the computers.

i tried this. With a + B + C disconnected from the main battery i had 12.6v at the the rear fuse box connection when the aux battery is connected up.

normal_Battery%20box%2010MY.jpg

But i only have 10.6v at the engine bay end of cable 'b' when it is not attached to anything.

If i connect it to cable 'c' i get 4.6v showing.

when setup like this the vehicle has no power to the ECUs

so hence the idea of running the computers off the aux battery this way doesnt appear to work.

putting cable 'c' back on the main battery makes everything power up as expected.

has anyone any suggestions on how to make this system work?

is it linked to the pyro device?

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  • 1 month later...

What's your ground for the second battery? I know the threads on fullfatrr.com usually go for one of the studs in the spare wheel foot well. A couple of volts drop across the length of an L322 is not inconceivable depending on current draw.

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Could you tell me what the piro device is? Is in in your picture?

Look at the positive battery terminal and you'll see a black box hanging down the side of the battery. It's a shaped pyrotechnic charge that in the event of a crash severs the positive battery lead. The aim is to disconnect the battery to prevent sparking and potentially ignite the fuel if there has been any split.

I thought it was only present on the 2007MY TDV8s though...

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I'll have a poke around mine tomorrow to see how your 10MY differs from my 07MY - I've got to swap over my battery anyway - conveniently dropped the almost new one that was in there when I was taking it out and cracked the case, not good :blush:, but picked up a new one a couple of days ago so will fit that one.

Whilst looking through the workshop manual though I've found references to an auxiliary battery compartment. I've can't place it though - it looks like it might be in the electrical box on the driver side of the engine bay but the pictures don't look quite right.

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