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GRND/negative when relocate battery to the trunk #1231454
05/11/12 02:42 AM
05/11/12 02:42 AM
Joined: Sep 2009
Posts: 393
Sweden
Snoddas Offline OP
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Snoddas  Offline OP
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Joined: Sep 2009
Posts: 393
Sweden
Hi,
Have started to take care of old (small) irritation problem on my white 64 dodge 330.
When start the car it have been a noice from the starter or some other electrical device.
Yesterday we start measure using an oscilloscope. We found a very big lack on voltage when start the car.
When we had measuring some spots the resultate was about 6 Volts to the starter.
After checking the voltage over starter relay we found that the realy close and open hole time under the starting of engine (that making the noice).

We took the battery and attach it directly at the starter and ground/negative direct on engine and the engine started great and without any bad sounds from start relay or starter.

For info the battery is new and are located in the trunk. The positive cable is 1 gauge and negative is ground in trunk floor (on engine the ground is attach to the firewall).

Its a lack of 2 V ground in chassie when we measured. Adding the lack of voltage in the postive cable and the voltage lack in battery when start/crank the car all that resulting 6 V at the starter.

I'm about route a good ground/negative cable from battery in trunk to the engine.

Strange, almost same battery setup in my 65 coronet havent any problem.

Stay cool.

Last edited by Snoddas; 05/11/12 02:45 AM.

1964 Dodge 330 Max Wedge clone
1965 Dodge Hemi A990 clone
Re: GRND/negative when relocate battery to the trunk [Re: Snoddas] #1231455
05/11/12 02:56 AM
05/11/12 02:56 AM
Joined: Feb 2007
Posts: 612
Nampa, ID
None2Slow Offline
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None2Slow  Offline
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Nampa, ID
When you ground the battery to the trunk, it is trying to transfer current to the engine. The body mounts may limit the current from reaching the starter. Try running the ground to the frame under the trunk. Make sure its clean and tight. Then run a ground from the frame to engine in the engine compartment. This "should" take care of your problem.

Re: GRND/negative when relocate battery to the trunk [Re: None2Slow] #1231456
05/11/12 03:34 AM
05/11/12 03:34 AM
Joined: Sep 2009
Posts: 393
Sweden
Snoddas Offline OP
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Snoddas  Offline OP
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Joined: Sep 2009
Posts: 393
Sweden
Thanks for the reply. Yes, that would be easier than route a long ground cable from trunk.


1964 Dodge 330 Max Wedge clone
1965 Dodge Hemi A990 clone
Re: GRND/negative when relocate battery to the trunk [Re: None2Slow] #1231457
05/11/12 10:05 AM
05/11/12 10:05 AM
Joined: Dec 2005
Posts: 799
Missouri
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bb74swngr Offline
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bb74swngr  Offline
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Missouri
Quote:

When you ground the battery to the trunk, it is trying to transfer current to the engine. The body mounts may limit the current from reaching the starter. Try running the ground to the frame under the trunk. Make sure its clean and tight. Then run a ground from the frame to engine in the engine compartment. This "should" take care of your problem.




I agree with None2Slow and it worked for me too:)


BigBlock 74 Swinger
Re: GRND/negative when relocate battery to the trunk [Re: bb74swngr] #1231458
05/11/12 10:29 AM
05/11/12 10:29 AM
Joined: Sep 2009
Posts: 393
Sweden
Snoddas Offline OP
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Snoddas  Offline OP
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Joined: Sep 2009
Posts: 393
Sweden
The thing is that it works now. I did some improvement on the negative cable where it is attached to the trunk floor.
I also installed a new cable shoe on the positive battery cable. The old one wasent that good installed.


1964 Dodge 330 Max Wedge clone
1965 Dodge Hemi A990 clone
Re: GRND/negative when relocate battery to the trunk [Re: bb74swngr] #1231459
05/11/12 11:21 AM
05/11/12 11:21 AM
Joined: Jan 2003
Posts: 8,940
Holly/MI
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Dean_Kuzluzski Offline
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Holly/MI
Sorry to split hairs, but there are no "body mounts" on a early B-body.

The factory engine mount "insulators" provide an electrical insulation too. If you have steel mounts or motor bracket you're good.

The K-member is directly bolted to the "Uni-body" framerails that has innumerable spotwelds tying them into the body.

The thin little "groundstrap" that goes from the engine to the firewall is really for the ignition electronics like distributor spark. Even though it's high voltage, it is actually relatively low amperage and that's where big thick wires are needed elsewhere.

Hence the stock battery ground went straight to the engine block/head and the positive cable went straight to the starter which ground to the block too.

As you add length to the cables, you add resistance, so cable gauge needs to get thicker/bigger (number gets lower).

Adding a remote starter relay further complicates matters. If there's internal resistance from low voltage cranking, burned/pitted contacts you're hosed.

Simple things like the size of the terminal/lugs and quality of the crimping/soldering done to transfer current can strand you. And as most know rust/corrosion and loose connections are bad too.

Keep it simple and go overkill.


R.I.P.- Gary "Coop" Davis 02/09/68-05/13/04
Re: GRND/negative when relocate battery to the trunk [Re: Dean_Kuzluzski] #1231460
05/11/12 12:50 PM
05/11/12 12:50 PM
Joined: Sep 2009
Posts: 393
Sweden
Snoddas Offline OP
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Snoddas  Offline OP
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Posts: 393
Sweden
Thanks for good information. We also find that out when measuring. If I remeber right it was about 0.5 Volts lack in the big (and long) postive cable.


1964 Dodge 330 Max Wedge clone
1965 Dodge Hemi A990 clone
Re: GRND/negative when relocate battery to the trunk [Re: Snoddas] #1231461
05/11/12 05:04 PM
05/11/12 05:04 PM
Joined: Jan 2003
Posts: 8,940
Holly/MI
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Dean_Kuzluzski Offline
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Dean_Kuzluzski  Offline
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Holly/MI
Quote:

If I remeber right it was about 0.5 Volts lack in the big (and long) postive cable.




Ok, you'll always have a little drop due to the length of cable. But, you're only as strong as your weakest link.

Also, the storage/usage of amperage is what is really the means to an end in the automotive starting system. Meaning, the 12-13.8 volts that the battery shows has to have the big amps to crank an engine and keep that level up. That's why MANY racers run TWO batteries in parallel. The current adds while the voltage remains the same.

High compression big block race motors with BIG valvespring pressure take lots of amperage to spin.


R.I.P.- Gary "Coop" Davis 02/09/68-05/13/04






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