Author Topic: Battery Cable Question  (Read 358 times)

racertb

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Battery Cable Question
« on: September 06, 2018, 12:47:19 AM »
All:

I'm ordering new battery cables...2/0 AWG 00, 36" for the starter switch side, 18" for ground.  Where is your ground cable attached?  Mine is attached to lower left transmission bolt, where it's been for years.  I've read in various forums (various 6V older cars) that some attach to frame?  Not sure it matters, but just curious.

Ted

chetbrz

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Re: Battery Cable Question
« Reply #1 on: September 06, 2018, 02:33:47 AM »
Ted,

My car also attaches at the transmission bolt.  This provides excellent electrical connection to the motor.  Since the motor is sitting on rubber motor mounts there is also a large copper ground strap on the passenger rear motor mount, connecting electrically the frame to the bell housing. 

As you know.., ground is the other side of the 6vdc electrical circuit for all components.  This ensures good electrical connectivity to all lights.  If you have any issues with dim lights keep this in mind.  Also there is a connection from the drivers side head bolt through a grounding block attached to the firewall.  This ensures good grounding to the cowl and dash assembly which is partially insulated by the wood framing. 

Hope this helps,  Chet...
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racertb

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Re: Battery Cable Question
« Reply #2 on: September 06, 2018, 05:25:02 AM »
Thanks Chet...the car seems to have always cranked a little slow even with a good battery.  I think my cables have always been small, but not too small like modern cars.  I want to make sure I've got the maximum power available.  The timing is good and I'd prefer to leave the spark control in when starting.

However, after reading your post, I crawled under the car and cannot find any strap, copper or otherwise, that is visible.  I'm wondering if it's missing, and if so, can you take a picture of where exactly it goes, length, etc.  If it's supposed to be on the lower right transmission bolt connected to the frame, nothing is there.  That could be part of the problem.  I do have the other grounding point from the driver's side head bolt to the firewall grounding block.

Ted

frankp

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Re: Battery Cable Question
« Reply #3 on: September 06, 2018, 03:05:32 PM »
For what it's worth, on my sedan, the ground strap, a flat cable, is attached to the frame near the battery.  I believe this is the original setup.  I remember the negative cable is closer to 24" in length.  The roadster ground has a cable to the tranny.
frank p

racertb

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Re: Battery Cable Question
« Reply #4 on: September 06, 2018, 03:58:48 PM »
Hi Frank, would you be able to take a picture?

Currently (and for many years), my battery (+ terminal) is grounded to the lower left transmission bolt and the other terminal (-) goes to the starter switch.

I'm curious if the strap was standard to all cars and if locations varied.  I'll take another look, but I couldn't find one.

Ted

Crazydave

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Re: Battery Cable Question
« Reply #5 on: September 06, 2018, 08:07:16 PM »
I believe mine is a flat strap as well. I'll take a look later to confirm.

Crazydave

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Re: Battery Cable Question
« Reply #6 on: September 06, 2018, 08:09:04 PM »
From an old picture in my gallery.

« Last Edit: September 06, 2018, 08:12:29 PM by Crazydave »

chetbrz

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Re: Battery Cable Question
« Reply #7 on: September 06, 2018, 10:26:12 PM »
Ted,

What is your goal.  Are you interested in historical correctness or a good conductive positive ground throughout your car.

Chet...
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racertb

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Re: Battery Cable Question
« Reply #8 on: September 06, 2018, 10:35:15 PM »
Chet - both, but correctness if I had to choose

Dave - thanks for pic.   Looks like battery connects to frame and starter switch and another ground from transmission to frame on passenger side?

I'm curious as to what is correct even though I'll probably wire up the way I have for now with bigger cables.   Would I need the other ground off passenger side?

chetbrz

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Re: Battery Cable Question
« Reply #9 on: September 06, 2018, 11:15:48 PM »
Ted,

This is the ground strap from my car which attached to the passenger side rear motor mount frame bolt and also attached to one of the two bell housing bolts that attach the bell housing to the motor mount.  I don't know if it is original component or added later.  I can say that without cleaning the stuck on grime it was almost unnoticeable. 



Anyway keep in mind that ground is an important conductor to your car's electrical circuit.  Paint, 90 years of corrosion to metal contact surfaces could greatly decrease your current flow.  Ensure that all contact points are clean and well connected.

I would consider Dave's car closer to historical accuracy.  If your ground was attached directly to the bell housing through the transmission bolt it was probably done to provide the most resistive free contact to the starter & motor.  Historically correct I can't say but most practical., I would vote yes.
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Crazydave

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Re: Battery Cable Question
« Reply #10 on: September 07, 2018, 12:26:05 AM »
Dave - thanks for pic.   Looks like battery connects to frame and starter switch and another ground from transmission to frame on passenger side?

I'm curious as to what is correct even though I'll probably wire up the way I have for now with bigger cables.   Would I need the other ground off passenger side?

No grounds on my transmission, the cable on the passenger side is the speedo.

Crazydave

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Re: Battery Cable Question
« Reply #11 on: September 07, 2018, 12:43:47 AM »

 Also there is a connection from the drivers side head bolt through a grounding block attached to the firewall.  This ensures good grounding to the cowl and dash assembly which is partially insulated by the wood framing. 

Hope this helps,  Chet...

Are you talking about about piece under the brake reservoir? I believe its purpose is limit the engine from twisting (torquing). It's rigid and has vibration damping, (shock absorbing) material behind it. I believe its insulated electrically.


I have the strap at the battery, goes straight to the frame. And the other strap Chet talked about on the passenger side.

This thread came up at a good time. I have been experiencing harder starts, starter struggling when gas starts entering (Choke). The lights are dim, I just figured they always sucked  :o. A few weeks back at the Nowthen show I left it over night, at the end of the day (total darkness) I was driving it across the grounds and noticed with the lights on it didn't have enough juice to run the horn.

Think I'll start with a clean up of all major electrical points of contact and see what happens.


frankp

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Re: Battery Cable Question
« Reply #12 on: September 07, 2018, 01:18:39 AM »
Here is my battery setup - like Dave's, as how I bought it in '65, but with new cables.  As barely visible, positive flat cable to the frame.  Negative cable to starter switch actually too long.  There is a flat cable like Chet has shown, although no pic at this time.
frank p

chetbrz

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Re: Battery Cable Question
« Reply #13 on: September 07, 2018, 01:28:51 AM »

 Also there is a connection from the drivers side head bolt through a grounding block attached to the firewall.  This ensures good grounding to the cowl and dash assembly which is partially insulated by the wood framing. 

Hope this helps,  Chet...

Are you talking about about piece under the brake reservoir? I believe its purpose is limit the engine from twisting (torquing). It's rigid and has vibration damping, (shock absorbing) material behind it. I believe its insulated electrically.

Dave, 

Yes the piece under the brake reservoir.  I also believed it was for dampening engine movement until I took it off the firewall.  The asbestos pad may allow for movement and dampening but the slide section is spring loaded from the top cover.  The top cover is pinned to the base with brass eyelets.  Why use brass ?  See picture below.



I checked with an ohm meter and it does conduct.  But probably not as good as a strap?  I am just puzzled by the brass eyelets.  Brass and copper are usually used for better conductivity. 

Another @#$@ Mystery

Frank et al,

It looks like I need to find a braided flat cable for the positive ground. 

Details, details...
« Last Edit: September 07, 2018, 01:32:20 AM by chetbrz »
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frankp

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Re: Battery Cable Question
« Reply #14 on: September 07, 2018, 01:46:09 AM »
The roadster was missing parts of this "absorber" but thanks to Dave, it is complete.

Chet, check your local auto store for the flat cable.  One near me has various lengths.  Give them a ringy-dingy.
frank p