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ground for battery in trunk.. this tab ok? #2694843
09/06/19 12:07 AM
09/06/19 12:07 AM
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Rancho Cordova, CA
Exit1965 Offline OP
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I was thinking of using this existing hole (minus paint of course) as a ground for the battery in trunk. Should that work OK?

Alternatively, I could go through the trunk floor and bolt something to the frame, but I'd rather not do that if this area of the body will work. In the engine compartment, I plan to run another cable from engine to body/firewall.

Thanks.

IMG_20190905_203602.jpg
Re: ground for battery in trunk.. this tab ok? [Re: Exit1965] #2694861
09/06/19 04:43 AM
09/06/19 04:43 AM
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70HemiGTX Offline
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Nope. Factory frame or aftermarket frame in the rear? If factory, I'd run one to the frame AND one all the way up to the engine block. Yes it is over-kill, but you can never have too good of a ground. Also the heaviest cable you can get your hands on.

Last edited by 70HemiGTX; 09/06/19 06:28 AM.
Re: ground for battery in trunk.. this tab ok? [Re: 70HemiGTX] #2694873
09/06/19 07:25 AM
09/06/19 07:25 AM
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Texas
GoodysGotaCuda Offline
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I wouldn't rely on that to start the engine on.

I made an aluminum bracket that tied to the two tie down hook points on the back of the RH rail on my 'Cuda. I do not have a battery to block ground, I have one solid battery to chassis and two engine to chassis grounds up front.

Last edited by GoodysGotaCuda; 09/06/19 07:26 AM.

1972 Barracuda - 5.7L Hemi, T56 Magnum 6spd - https://www.facebook.com/GoodysGotaHemi
2020 RAM 1500
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Re: ground for battery in trunk.. this tab ok? [Re: GoodysGotaCuda] #2694896
09/06/19 09:43 AM
09/06/19 09:43 AM
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Ontario, Canada
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Stanton Offline
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Will it work ... YES. Been there, done that.

Was checking the plugs one day and dropped the last plug and it hit the starter positive and shorted. I heard a BANG that sounded like a gunshot come from the back of the car. My first though was that the battery had exploded but when I opened the trunk it was intact. A subsequent search revealed the ground had blown off. It was one of those thin stamped copper ends and it had blown off at that contact point. Kinda lucky it did I guess !! So there's something to be said for having weak points in systems !!

Re: ground for battery in trunk.. this tab ok? [Re: Exit1965] #2694899
09/06/19 09:57 AM
09/06/19 09:57 AM
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Looking for a way out of Middl...
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I run mine to the trunk latch bolt. Worked fine for years.

Always run a negative wire smaller than the positive wire running to the front. If the positive wire grounds and they are the same size it will burn both wires sparking a fire along the whole car. If the ground is smaller, only the ground burns and it will be limited to the trunk. Kinda like an emergency fuse. I suggest at least 2 sizes smaller.

For those who think it won't happen it did to me. Trunk filled with smoke but the car was OK. There are other methods that help prevent it but even with those in place this method costs nothing to do. One method is to put a solenoid on the positive going to the starter in the trunk so the main battery cable is not live all the time but it still has to go live to crank. If it goes live to turn the starter and the positive wire is grounded it will still burn the car.

twocents

Re: ground for battery in trunk.. this tab ok? [Re: 70HemiGTX] #2694915
09/06/19 10:32 AM
09/06/19 10:32 AM
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Omaha Ne
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TJP Offline
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Originally Posted by 70HemiGTX
Nope. I'd run one to the frame AND one all the way up to the engine block. Yes it is over-kill, but you can never have too good of a ground. Also the heaviest cable you can get your hands on.


iagree

Re: ground for battery in trunk.. this tab ok? [Re: TJP] #2694935
09/06/19 11:21 AM
09/06/19 11:21 AM
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Ohio
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jlatessa Offline
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We welded a 3/8 bolt to the sub frame beneath the trunk mounted battery and one to the front sub frame
passenger side, (we have welded sub frame connectors). 2/0 size cable.

For the positive, ran a 2/0 from battery to an insulated stud mounted on the firewall,
have a homemade screw on cover for that connection to eliminate any accidental contact

I do like the Idea of a lesser gauge ground to act as a fuse and will change one of the ground cables to have that safer set-up.

Thanks for the input ....Joe

Re: ground for battery in trunk.. this tab ok? [Re: TJP] #2694939
09/06/19 11:31 AM
09/06/19 11:31 AM
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SW CO
HemiSportFury Offline
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I've used that spot without a problem. Clean both sides and use large washers of both sides to ensure a large contact area. I do have an aircraft circuit breaker on the positive side that also serves as a battery disconnect/anti-theft device.


'64 Sport Fury, 528 Hemi, FiTech EFI, 4-speed, 4.10 Dana 60
'57 Belvedere 2dr sedan, current project in process
'19 Cherokee Trail Hawk Elite
'03 Ram 2500 CTD HO, 6-speed 214,000 miles and still going strong
Re: ground for battery in trunk.. this tab ok? [Re: HemiSportFury] #2694971
09/06/19 01:38 PM
09/06/19 01:38 PM
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So Near, Yet So Far
topside Online content
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I've used that location, a similar factory hole at a rear body panel gusset, and similar holes at the trunk latch support.
Worked fine in every case, whether a 512" Duster, various vintage race cars, early B bodies. My car in the avatar's been that way for over 30 years.
I also always add a heavy ground cable from block to chassis.
Fasten all ends as previously noted, and I like star washers to dig in.
On a unibody car, the chassis and parts welded to it become the "frame".
On something with a separate body/frame construction & isolators, I add ground cable frame/subframe to body.

Re: ground for battery in trunk.. this tab ok? [Re: topside] #2694975
09/06/19 01:50 PM
09/06/19 01:50 PM
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Pasadena, Texas
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fal3 Offline
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What 70gtxhemi said. I drilled a hole in the trunk floor near the battery & ran the ground wire to the frame. Did that 20 years ago and has been ignored since then.

Re: ground for battery in trunk.. this tab ok? [Re: Exit1965] #2694976
09/06/19 01:53 PM
09/06/19 01:53 PM
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Aurora, Colorado
451Mopar Offline
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Yes, that location works for a chassis ground, and it has worked on my Charger for 25 years, but you may get a bit less charging voltage at the battery?
If running EFI, or other computer stuff, it would be good idea to run another ground from the battery to the computer equipment, and not ground it to the chassis ground.

Re: ground for battery in trunk.. this tab ok? [Re: 451Mopar] #2694998
09/06/19 03:17 PM
09/06/19 03:17 PM
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Ontario, Canada
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Stanton Offline
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Normally the battery grounds to the block and then to the body. So the current has to travel through a solid block to get to the starter. Whether it runs through an iron block or a steel chassis is neither here nor there, what matters is the connection between each. Typically the ground from block to body was a much thinner gauge than from the battery to block because the starter needed that heavy gauge for the current draw. So grounding first through the body and then to the block you're going to have to use heavy gauge at both ends.

Re: ground for battery in trunk.. this tab ok? [Re: Exit1965] #2695010
09/06/19 03:55 PM
09/06/19 03:55 PM
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Oregon
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AndyF Offline
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That tab will work just fine for a chassis ground. You'll still need to run another cable up to the engine block for an engine ground. There are a lot of amps that need to flow back and forth between the battery, starter and alternator. Your ground cable running to the engine should be at least a #8 welding cable and something like #4 would be even better. You can get high quality multi-strand welding cable from Amazon. The more strands the better.

Re: ground for battery in trunk.. this tab ok? [Re: AndyF] #2695146
09/07/19 09:43 AM
09/07/19 09:43 AM
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70HemiGTX Offline
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It was mentioned to run a smaller ground wire as a "fuse". Why not just go to NAPA and buy a 100 amp ( I think that is what I have in, but not sure.) fuse and put that in the positive cable right at the battery. Much safer than relying on a homemade "fusible link". NAPA has different amp fuses for them. Very nice item. Not real expensive either. Remember even though your ground wire burns off, your positive wire still has power in it, making it a possible arc point. Fusing it right at the battery limits the amount of powered cable to a few inches. I tried to attach a photo of the fuse I used. Don't know if it worked or not.

NAPA part #


BK 7821143

Lists for less than $12.


Last edited by 70HemiGTX; 09/07/19 09:47 AM.
Re: ground for battery in trunk.. this tab ok? [Re: AndyF] #2695163
09/07/19 10:33 AM
09/07/19 10:33 AM
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Aurora, Colorado
451Mopar Offline
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Oops, I did forger that you still need to run large ground cable from frame to engine block. Thanks for pointing that out guys.

Re: ground for battery in trunk.. this tab ok? [Re: 451Mopar] #2695169
09/07/19 10:58 AM
09/07/19 10:58 AM
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north of coder
moparx Offline
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never a good idea to run small cable for the battery ground. doing this, eventually will cause problems you can't imagine, and WILL cause you to loose hair you don't have.
just relaying my experience in fixing wiring problems over the years.
and if you are contemplating new battery cables and even THINKING about those cheep-o bolt on cable ends at the battery, 50 lashes with wet noodles you shall get ! tsk rant spank
beer

Re: ground for battery in trunk.. this tab ok? [Re: moparx] #2695183
09/07/19 11:26 AM
09/07/19 11:26 AM
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The stuff that we got away with 30 years ago doesn’t work as well as it did back then. Everything is electronically controlled now so do it right and reap the benefits. Good grounds are so important


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Re: ground for battery in trunk.. this tab ok? [Re: moparx] #2695303
09/07/19 09:00 PM
09/07/19 09:00 PM
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Lincoln Nebraska
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RapidRobert Offline
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Quote
and if you are contemplating new battery cables and even THINKING about those cheep-o bolt on cable ends at the battery,
can you get small gauge (large) molded cable battery terminal ends?


live every 24 hour block of time like it's your last day on earth
Re: ground for battery in trunk.. this tab ok? [Re: Exit1965] #2695347
09/08/19 12:33 AM
09/08/19 12:33 AM
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I've used that hole ground to bare steel on both sides and another same size cable to one of the trunk latch bolts ground to bare steel also as well as two #4 wire block to frame grounds up front up
I used one of the threaded holes by the starter in the frame and the bottom lower 7/16 bolt through the block to the tranny case and one from a 7/16 engine mount bolt on the block down to one of the k frame engine mount bolts on the passenger side, clean all the surfaces to bare metal first up wrench grin


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: ground for battery in trunk.. this tab ok? [Re: 70HemiGTX] #2695408
09/08/19 11:06 AM
09/08/19 11:06 AM
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Looking for a way out of Middl...
IMGTX Offline
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Originally Posted by 70HemiGTX
It was mentioned to run a smaller ground wire as a "fuse". Why not just go to NAPA and buy a 100 amp ( I think that is what I have in, but not sure.) fuse and put that in the positive cable right at the battery. Much safer than relying on a homemade "fusible link".



Starters can pull more than 100 amps. It's not about fusing the auxiliary systems it's about protecting the main power wire to the starter. I have had the starter come loose and when I went to start the car that is when all heck broke loose. Factory trunk mounted cars use a similar method or use non burn wiring covers(like a fusible link has) to prevent the car from burning if the main trunk line gets shorted.


Like you pointed out though. Auxiliary systems should always be fused with a fuse or fusible link.

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