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Battery trunk relocation options

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2 hours ago, xr4tic said:

I just got my AG battery, 3 lbs. I already had removed the original tray because I was going to mount in the trunk, but that doesn't make sense with a 3 lb battery, the long cables would weigh more than that.
I'll mount it close to the stock location
f00ce006d07af6be22b4c3d8ec82241e.jpg
f764590ce2a63d10415333f72c983cea.jpg

Sent from my SM-G975U using Tapatalk
 

 

How's that thing crank? I thought people used two of those daisy chained together. 480 CCA seems pretty low. 

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7 minutes ago, Mucci said:

How's that thing crank? I thought people used two of those daisy chained together. 480 CCA seems pretty low. 

 

Not sure yet, I'm still working on re-wiring the engine bay.

 

@NYNick is running this battery and seems to like it, so I pulled the trigger on it.  The PC680 referenced earlier in this thread only has 170 CCA and I think there are a few running that battery.

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(edited)
On 7/26/2019 at 6:47 AM, xr4tic said:

I just got my AG battery, 3 lbs. I already had removed the original tray because I was going to mount in the trunk, but that doesn't make sense with a 3 lb battery, the long cables would weigh more than that.
 

 

Figured I would weigh the difference since I'm mid project and have a postage scale...

 

Here's the weight of the E36 positive battery cable to trunk, negative cable, junction block, and "junction to starter cable" (in this case it's the stock 02 positive cable.)

 

20A8EEBC-EFCD-41AD-A6C1-DC42385BE775.thumb.jpeg.7dbefd924093e34adc36c139392fc750.jpeg

 

5lbs 2oz. 

 

With the stock 02 positive cable removed

 

00EFB06A-282F-4AB6-9A1E-455E19A56342.thumb.jpeg.f7a22d520cdce9674e0cc8cf10eb4606.jpeg

 

4lbs 10oz. 

 

So the stock + cable is about 8oz. I'd say the stock ground strap is about the same length but braided and likely lighter. Let's say it's 6oz. 

 

So the added cable weight to relocate a battery to the trunk is an additional 4lbs 4oz (+/- 2oz.)


Removing the tray would save something too I guess. Maybe another few oz. 

 

This is of course pretty rough but yes you are correct that running the 3lbs battery up front instead of in the trunk saves you about 4lbs in addition to the 30 or so you are saving over lead acid. 

Edited by Mucci

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(edited)

Guys for those that drilled their rear shock mounts/towers, how did you protect from tin worm, I’m thinking primer and good quality rust paint, I would then give them a liberal spray up inside the mounts from under the car with anti rust treatment spray Such as Bilt Hamber cavity wax / under body or such like?

Edited by SydneyTii

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If you go through an existing hole to the rear seatbelt mounting bolt you don’t have to drill any new holes. 

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(edited)
2 hours ago, Mucci said:

If you go through an existing hole to the rear seatbelt mounting bolt you don’t have to drill any new holes. 

I'm thinking more about the shock mounts where the brace/battery holder will bolt to.

Edited by SydneyTii

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Don't do it. Either go under your rear seat or lightweight battery upfront in the stock location. There is no reason these days to relocate your battery. Even an AGM would work but I like the LI-Pho.

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(edited)

Pending M42 swap necessitates that I move the battery. Initially I thought trunk as well but after reading numbers of these threads I decided under the rear seat (delete) was the best place for me. I also was not a fan of the idea of the battery near gas fumes, battery getting in the way of cargo or shorting out if something contacted it, etc.

49890637367_73c52ab7a3_b.jpg

Edited by Spyke

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10 minutes ago, Spyke said:

Pending M42 swap necessitates that I move the battery. Initially I thought trunk as well but after reading numbers of these threads I decided under the rear seat (delete) was the best place for me.

49890637367_73c52ab7a3_b.jpg

good location and choice of battery.  i had that same one.  lasted 7 years.

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On 7/26/2019 at 12:09 PM, Mucci said:

 

Figured I would weigh the difference since I'm mid project and have a postage scale...

 

Here's the weight of the E36 positive battery cable to trunk, negative cable, junction block, and "junction to starter cable" (in this case it's the stock 02 positive cable.)

 

20A8EEBC-EFCD-41AD-A6C1-DC42385BE775.thumb.jpeg.7dbefd924093e34adc36c139392fc750.jpeg

 

5lbs 2oz. 

 

With the stock 02 positive cable removed

 

00EFB06A-282F-4AB6-9A1E-455E19A56342.thumb.jpeg.f7a22d520cdce9674e0cc8cf10eb4606.jpeg

 

4lbs 10oz. 

 

So the stock + cable is about 8oz. I'd say the stock ground strap is about the same length but braided and likely lighter. Let's say it's 6oz. 

 

So the added cable weight to relocate a battery to the trunk is an additional 4lbs 4oz (+/- 2oz.)


Removing the tray would save something too I guess. Maybe another few oz. 

 

This is of course pretty rough but yes you are correct that running the 3lbs battery up front instead of in the trunk saves you about 4lbs in addition to the 30 or so you are saving over lead acid. 

Hi,

 

It's also about weight distribution.  Even with the added 4 lbs. of cabling, by relocating the battery you lighten the far corner of the car.  If you factor in moment arm, the benefit of relocating is greater than the weight alone would suggest.

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I would do under rear seat. Mine came with trunk mount and it takes up way to much space in the trunk.

Plan to do under seat at some point in future,no hurry for now.

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Wherever you put your battery, you want 'the path of least resistance' between your current source and your largest current sink. That means a single continuous suitable gauge cable from battery + to the Starter Motor....every additional fuse/isolator/junction adds resistance & creates potential points of failure. On an '02 its easy to extend the red cables from loom/alternator so that they all connect to the Starter post - this becomes your junction point - no extra hardware required.

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10 hours ago, NYNick said:

Don't do it. Either go under your rear seat or lightweight battery upfront in the stock location. There is no reason these days to relocate your battery. Even an AGM would work but I like the LI-Pho.

I hear you Nick, but I’ve had the battery and tray out a few times lately with alternator issues, WUR work, oil change etc, and being a Tii it’s a poor spot for a battery, if I move it, it creates a good deal of space and for me that’s still a great reason to get it out of the engine bay, and given my car is solely a weekend car now I’m certainly not worried about the trunk space. I realise the under seat location is a good idea for most,  but clambering about in the back of an 02 and pulling up the seat base to me isn’t that simple either, not that you need to do that very often, I have a few old sport injuries that make it a bear.

The trunk is easy to access, there’s plenty of room, you can tie off to it, and if I don’t like it I can just blank off the holes with grommets like all of the other holes that were made for cavity wax penetration in my car.

Im not seeing many negatives with moving it other than the dreaded drilling the shock mounts.

 

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The PO has moved the battery to the trunk.  It was sitting in the corner, I found this cool mount for the Optima.  It doesn’t take up much room and has a handy cutoff. 

6F79B4D3-48E5-4964-866F-98272139C178.jpeg

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