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Battery in the Boot

Im looking to move the battery to the boot of my HQ but im just curious does the earth need to come all the way back to the black to make earth or can i just use the boot floor as a suitable earth ?

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I would run the earth up to the front with the positive. You may need very heavy duty/good quality cables to account for voltage drop. I also think you will have to have some type of breather system expelling the battery gases to atomsphere. Battery gases are explosive. Someone here who has done this may know more.

Cheers
Keith

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Cheers
Keith

"does the earth need to come all the way back to the black to make earth"

Yes. Further info here ... http://holdenpaedia....

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Not do it to a street car.

Shane.

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to do it properly you need some large cables and there very expensive

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I have never run an earth to the front. Do run a heavy gauge +ve though, O gauge as a minimum..

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"If the Battery -ve Lead is not run to the Engine Block the current that returns from the Battery under starting will be forced to follow a complex and damaging path through the Drivetrain where all the Gearbox, Tailshaft and Rear Axle Gears and Bearings will become pitted."

What provision do you make in your Cars to prevent this from happening?

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T

My Shed

Holdenpaedia, they're the brakes Mate.

just a short thick lead from engine block to chassis with good contact would suffice, I am sure.

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She was just a whiskey maker, but I loved her still.

[http://gallery.oldho...|toybox]

You want the Starter Current to run through the Body?

What convinces you that the Body will take over 200 Amps without consequence?

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T

My Shed

Holdenpaedia, they're the brakes Mate.

fitted between the mounting bolts on the transmission mount. One end is fitted to a bolt holding the mount to the trans and the other end fitted to a bolt holding the mount to the crossmember. You can see it in the pic below. It is a flat braided copper strap that has been covered in black heatshrink to make it blend in..

http://gallery.oldho...

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Where does the Battery Negative connect?

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T

My Shed

Holdenpaedia, they're the brakes Mate.

The lead is only 30cm long, 3 gauge, and connects straight to the chassis. When voltage was measured under load there was less than 0.1volt variation between all measurements.

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I also have a concern about passing Starter Current through the Gearbox. Has the Gearbox manufacturer sured the unit up for 200 Amps?

I'm picturing a bunch of Gearbox Bolts with Loctite on them providing great insulation and Gaskets on the mating surfaces providing additional Insulation.

That would make the Starter Return Current run from the Block into the Crankshaft via the Main Bearings, then out of the Gearbox through its Bearings into its Casing, then to the Chassis then to the Battery.

Also the Ignition return path is through the Chassis which has the potential to develop corrosion.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

In the avaerage EFI car many and varied earth points are utilised within the wiring harness. For example the engine alone has 4 thick earth wires that bolt directly to main bolts on the motor. These wires then continue to sizable bolts/studs mounted to the body. All lighting has it's own earths and in many cases the earth is actually the switched side of the circuit. In my case many earths go back through the BCM (body Control Module) and any variation of the load sensed by the BCM can be interpreted as a blown globe, fuse or other component. Stray earths and poor earths are a thing of the past. The gearbox casing will easily handle the current requirement of the starter, remembering the starter is engaged for only a few seonds at a time. There are 6 x 3/8" bolts holding the trans to the engine so no real concerns with voltage drop and finally there are no gaskets, seals, sealants or the like between the trans, engine and starter. I don't forsee a problem. I have added an earth connection to the radiator even though it's solid mounted and also one to the fuel tank as it is insulated with neoprene and silicone..

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All that could have been so easily avoided by adhering to the original design i.e. running a return Starter Cable between the Block and the Battery -ve.

"I have added an earth connection to the radiator "

I thought you said this wasn't necessary.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

I added the radiator earth just to be doubly sure.
Just for your own interest I've added a link below of the battery installation in a new current VE Commodore. They do not run an earth return cable to the motor. Just a simple cheap short earth cable straight to the chassis. I think this is an example of where the 100% theoretically correct method is just not needed and does not offer any advantages just complexity.
The first EH I built in 1982 runs my design setup and there has not ever been an issue with it.

http://gallery.oldho...

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It does give another aspect to think about... i know T knows his stuff so i generally would go with his thoughts but i have always known everyone to just run the earth to chassis without problems. If holden is now doing the same do they have some failsafe setup so there isent current flow through the driveline ?

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"They do not run an earth return cable to the motor. Just a simple cheap short earth cable straight to the chassis. I think this is an example of where the 100% theoretically correct method is just not needed"

I think it's an example of throwing the baby out with the bathwater. Anything to keep costs down, or maybe the designers just didn't know what they were doing, sort of like our current economic environment where the whole world has had to fall back on the Keynsian model it abandoned as being passe.

"and does not offer any advantages just complexity."

I can't think of a simpler solution to the potential damage to the Engine, Gearbox, Diff and Bearings in the Rear Axle than fitting 3 metres of cable between the Block and Battery -ve. Just the way GMH shipped all their Holdens right up to VK at least, a solid Earth from the Block directly to the Battery -ve just like in this photo ... http://holdenpaedia....

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T

My Shed

Holdenpaedia, they're the brakes Mate.

The differential is insulated from earth by all the rubber mounting bushes. The only connection it has to earth is the uni joint caps. Why would the starter try to ground itself through diff when the resistance would be significantly higher than through the large zero resistance earth strap fitted. It makes no sense. The starter will earth through the 50kg engine block which in my case is connected to a 10 kg transmission case which is connected to the chassis by a 75 square mm earth strap. Why would it try to divert the earth path through oil insulated gears and bearings. In my opinion that makes no sense. I agree with the theory you are using I just don't see it being realistic.

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There is no intention to electrically Earth the Rear Axle. If it is rubber insulated for Suspension reasons, fine, but what is the Electrical Rating on the Rubber? Who tested the Rubber and to what standard?

And the Brake hoses? How does the Brake Fluid react to current? What standard does this conform to? What will be the effect of current grounding through the Braking System? Any ABS connected? Any low Fluid Sensor connected?

Any Brake Pad Wear limit equipment connected to the Car that will be sensitive to Starter Current.

The Starter Circuit resistance is very low.

At 200 Amps and 12 volts, the total Circuit Resistance will be .006 ohms. I'm not sure anybody designed the Body with such a low resistance in mind. My view is that they just don't care about any side effects because a modern Car will be junked much earlier than an OH.

The potential to blow very expensive Electronic Gear is fantastic would be and a crippling blow to the owner.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

What if the current were to pass through the windscreen washer water, what if the driver has loose change in their pockets. T you are thinking way too hard. Don't over think things. If the battery has a clean "zero" resistance path through the body shell it will take it. Why would it try to earth through all these other "high" resistance paths, it just makes no sense. If your worried grab your multimeter and measure the voltage across the earth terminal and any point on the car, I'm sure you will find the lowest reading at the engine block regardless of how the battery is connected and where it is located.

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What if the Car hit a bump and wore through a suspension Rubber? The next start would be a spectacle. Big Smoke!

You raised the point about the Rear Axle being electrically isolated while it has metal Brake Hoses connected allowing direct conduction to the Brake Fluid from the Axle Housing.

I think the few dollars you and GMH are trying to save has dug a big hole for you both.

The original poster asked if he needed a return and you told him he didn't. It's taken pages and pages to cover only some of the contingencies involved in saving a few metres of Welding Wire.

If he is using any one of the common Gearboxes available to HQ, then my reply about their being no intention for any of them to carry 200 amps still stands.

If he is using any kind of special Aftermarket Gearbox I'd strongly recommend he query the manufacturer to find out if the unit can withstand the repeated exposure of current high enough to melt it. Likely the same amount of current that was used to weld the Body together.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Has a transmission engineer ever rated a gearbox housing for current rating NO. Why bother. To me it is totally illogical to think that a casting the size of a transmission case could not withstanding 200 amps all day long and have no ill effects.
Welding car bodies together, my guess 150amps at the absolute max, relevance unknown.
A point raised earlier was to use welding cable. This is also a bad idea as the total cross sectional area of a given diameter of welding cable is far less than the equivalent diameter automotive cable due to the smaller diameter of each individual wire. Yes there are more conductors but the overall area is smaller. This is a mistake people regularly make.
Again, I agree with your the theory you state BUT it is simply not relevant. Many people including those well respected as knowledgable on this site have stated that from many many years of combined experience the short earth cable to the chassis combined with a similar cable from the driveline to the chassis is 100% functional,reliable and relatively cheap. These are all the characteristics a car manufacturer wants hence the implementation of this setup on the cureent Commodore and mny other cars running rear mounted batteries, surely they can't all be wrong.

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"it is simply not relevant. "

It was relevant for all the previous 12 volt OH's and with good reason.

I think GMH learned their lesson on the 6 volters as the images show (ground strap at the nearside Gearbox Mount).

By your reasoning, abandoning through the Body grounding practice (as in FX-FJ) in favour of the newer 12 volt grounding system (block directly to the Battery -ve) was because they knew what they were doing?

They even moved the Battery Closer to the Starter and this after doubling the voltage and halving the current.

So are you saying that going back to the previous abandoned model is electrically prudent after maintaining the new model for decades and abandoning the other after only 8 years?

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T

My Shed

Holdenpaedia, they're the brakes Mate.

This is going round and round in circles. Again I will say it's an example of the theory not being reproduced in the real world.
To use your reasoning is to say that Holden has now gone back to a system they discarded 50 years ago. This is saying they are wrong again and the whole world will end.
Mountains out of mole hills. If it works don't change it. The car manufacturers are happy it works and they use it, what more can I say to convince you.

I'm signing off because the movie just finished and the cricket is boring, good night all...

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Me too.

People have posted up here about Gear Selectors sparking under cranking because the Block Earth came loose or was missing. That's how bad things can come to be.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

I have seen melted accelerator cables and siezed throttle linkages from poorly earthed engines.

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Where would i be able to get a thick enough and long enough wire T ???

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Welding Cable has the right category of Current Rating.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Many brands make it. I personally use MATSON as it's a well respected Aussie product. Brands like NARVA, AERPRO import cheaper asian alternatives. Most decent auto stores carry it, however if you get it from your local Auto Elec he can also crimp the end fittings for you if you want him to. Personally I solder mine.

There's a folder in my shed showing my setup.

http://gallery.oldho...

http://www.matson.co...

http://www.narva.com...

http://www.aerpro.co...

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I can fully empathise with T and also Scot - myeh. Both have valid points. I personally will not run a battery in the boot if I can avoid it especially on cars where there isnt any gain other than aesthetic.

I build hot rods in amongst other cars and boot or rearwards mounted batteries are pretty much a given. In those situations I run a flat braid earth strap from the gear box to the chassis- nearest the starter. The battery earth is connect straight to the body. I found running a long earth lead wasn't great. The several different auto sparkies I used over the years all said the same thing - run a earth strap not miles of cable.

My biggest issue with batteries mounted away from engines is the fact it becomes a pain when working on the motor doing tune ups etc. If you have a car that has starting problems - like its run out of fuel and you flatten the battery getting it going again then having to be at two ends of the car is in my books just flaming annoying.

For my Holden builds I now run the battery back up the front - less hassles and makes life easier. Who cares what it looks like and losing the weight to the back of the car isnt reason enough for me to warrant changing my ways.

Cheers streetneat -Andrew.

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Cheap, Fast, Good - pick two.
If its cheap and its fast - it wont be good.
If its good and its cheap - it wont be fast.
If its fast and its good - it wont be cheap.

StreetneatShed

Current will take the path of least resistance, therefore whatever you do ensure that your connections are clean, rust free, and tight using proper connections for the type of cable.

Welding cables are inherently more flexible than solid stranded cable thus easier to route through the nooks and crannies.

http://www.stealth31... seems to be good starting place...

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Mines in the boot. It runs a heavy positive cable from the battery. Earth strap goes to the floor in the boot and another from the firewall to the block. Never had any issues with voltage's under load.

Im sure if it was a problem, my autosparky bro in law would have pointed them out.

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*

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'i'm definately shore that guage wont work with my tuff bango diff and Opal sydcrome box,if it goes though my grill,and I put the breaks on I realize its better with the glimer belt & tunned holly and Ederbrock duel feul webber gaurds, wiht etc primmer.'

Can I un-mark this thread? I actually read those most recent posts and it has clearly become ridiculous - for exactly the same reason as used to often happen here.
Sigh...

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'i'm definately shore that guage wont work with my tuff bango diff and Opal sydcrome box,if it goes though my grill,and I put the breaks on I realize its better with the glimer belt & tunned holly and Ederbrock duel feul webber gaurds, wiht etc primmer.'

I snapped this pic in a customers workshop yesterday. Ford now is following Holden and no longer connecting the battery negative terminal directly to the engine block. Both now rely on an earth strap from the chassis to the engine.

http://gallery.oldho...

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I thought you abandoned this thread?

Are you saying that the populace running after an idea like so many lemmings makes a basis for sound practice?

I can picture the transients generated at all those earth points by the mother of all back EMF generators (the Starter) and all those dissimilar metals reacting.

If there is anything occurring in new Car building, it's decreasing longevity driven by an ever more fickle public and anything that can save the Manufacturer one dollar they will dive after.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

I have an Alfa Romeo 164 that has a 210hp V6, has 6 individual ignition coils on plugs, every accessory on earth including sunroof and an electronically shifted ZF auto transmission. That has the battery in the boot and it is grounded to the body inside the boot itself. About 6" length cable. That is the factory setup. Look around if you are not sure. Need more convincing to not to worry? :-)

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___________________________________
Tharanga

1972 Volkswagen Beetle
1974 Holden HQ
1993 Alfa Romeo 33
1996 Alfa Romeo 164
1997 Nissan Sunny SB14

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