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Battery earths - where should I put them


MogLite

Battery earths  

21 members have voted

  1. 1. Where should I connect them

    • Drill a hole through the 3mm bulkhead
      12
    • Weld a tab onto the roll-cage and bolt to that
      5
    • Route the wires to the chassis
      4


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I've got on my to-do list for tonight - connect the earths for the batteries

The batteries are here

IMG_4036.jpg

Routing the earths to the chassis is a PITA as it will have to be through a hole in the floor and then a hole in the chassis.

With a cage that is welded everywhere - I could weld a couple of tabs to that and bolt the earths to that.

But even easier - the bulkhead is 3mm steel, seam welded, so I figure, why not just drill holes through that, scrape of some paint and bolt the earths to that.

The starter motor and rear winch are both earthed through the actual chassis, but with so much stuff welded to it, I reckon I might as well keep it easy.

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i've always heard its best to connect earths from the winches to chassis and straight back to negative on battery. i have no back up info to prove this, but the person who told me i would bow to his superior knowledge.

completely OT, colour coded tyres aswell?!?!?!?! :rolleyes:

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On the 90 I have earths fron engine to chassis, gearbox to chassis, chassis to battery. The gearbox and battery earch cables are attached to the chassis at the same point to improve the connection. Winch will be earthed back to battery directly and maybe also to chassis to provide an alternative path in case of connection problem with main earth.

Oh and voted for bulkhead, if it's all welded together then the chassis/cage/bulkhead are essentially electrically connected so it I can't see it making much difference to the connection. I'd still be tempted to earth the winch directly back to the battery though.

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As the cage is welded to the chassis its all the same.

Its the quality of the earth connection that will make the difference, poor earths have caused me tears in the past.

Use welding cable to 35mm2 stuff much more flexible

Place it somewhere you can easily get to when finished, and NOT where treews roots branches etc can get to it

Nige

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Winch earths as side (because I reckon that needs to go straight to the battery, I've been on the other end of chassis earthed winches and the results are poor IMHO) I reckon the baulkheads a good bet. It keeps the cable short and tucked away so it doesn't snag and is nice and thick.

BTW Its looking very nice, Andy :D An excellant demonstration of the correct use of orange on a vehicle ;)

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Get a couple of M10 mild steel bolts, drill through your bulkhead and weld the bolts to the bulkead, these will then act as your earth points, you can further improve this by welding a penny washer on the side of the bulkead where your connections will be to give you a flat surface, then run your battery lead to this and a lead from that then onto the engine such as a mounting for the starter motor to give you the best earthing possible for the starter/alternator et cetera.

M10 is major overkill, PANAVIA standards on Tornado only require a M6 earth stud for 30-100Amps at 28VDC, primarily due to the size of cables going to it rather than current, as the current will flow through the contact surfaces of the ring crimps and through to the bulkhead rather than down the stud/bolt, so an M10 bolt or two will do you good.

However don't rely on the chassis/roll gauge to provide you an earth path, a decently made cable and properly assembled with bonding point paint will give you many years of faultless bonding.

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I would vote for none of the above!

Run the earth cable to one of the starter motor mounting bolts and from there to the chassis via a bolt welded to chassis.

Run the earth for a winch directly to the battery.

Use as heavy cable as you can for earths - at least 35mm.

What is the one thing in the vehicle which draws the most current - the starter. The Alternator is also earthed through the engine. give them both the best chance by making your engine the primary earth. All the bulbs, radios & stuff can connect via the weedy earth strap (or choke cable ;) ) you've run between the engine & chassis.

Si

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Excellent advice and cross-section of opinions as always :)

I didn't get chance to do the earth connections last night, but as the bulkhead is the clear winner, and easiest, thats is what is going to happen.

I've also got engine and starter motor earths on my to-do list.

When I say I've earthed the winch through the chassis, I mean properly by taking an earth connection off of the motor and earthing that to the chasiss, rather than merely relying on the body of the winch, and mounting bolts to provide an earth.

Seems pretty easy to extend this connection to the battery, so I might as well belt and braces it ;)

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I would vote for none of the above!

Run the earth cable to one of the starter motor mounting bolts and from there to the chassis via a bolt welded to chassis.

Run the earth for a winch directly to the battery.

Use as heavy cable as you can for earths - at least 35mm.

What is the one thing in the vehicle which draws the most current - the starter. The Alternator is also earthed through the engine. give them both the best chance by making your engine the primary earth. All the bulbs, radios & stuff can connect via the weedy earth strap (or choke cable ;) ) you've run between the engine & chassis.

Si

Si has said almost exactly what I was thinking.

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Im gonna don tin hat and argue (just for the fun of it) making the following assumptions;

the cross section of Andy's cage equates to 424mm2 of mild steel (agreed not as good a conductor as copper multistrand but not resistance against cross sectional area still gives is an advantage in terms of voltage drop over cable)

The Engine is (on standard mounts) isolated from the chassis reliant on earth straps for continuity to the chassis (bar prop shafts etc and other spurious contacts), an average starter motor is 3kW and doesnt run for a long time.

the only issue I see with not using the chassis as a common earth is the current handling capacity of the connections you use, if the chassis has studs or posts welded to it (same profile as battery terminals) then short cable runs could be used to tie the earth return of the winch to the chassis and the battery negative to the chassis - effectively dropping voltage loss and increasing efficiency..........

hides in trench with packet of choccy bourbouns.......... :ph34r:

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The drawback I can see with that is you are introducing two more connections between the winch and battery. Connections are fine when new if done well (and I'm assuming they would be) but if not kept clean dry and corrosion free the resistance and hence voltage loss of connections tends to go up over time. 'kin big wire with as few connections possible is my choice, and an alternative path is also preferable, so do both. Then if you have a resistance increase in a connection it shouldn't impact so much on winch performance.

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Cable deteriates with time, unless you are using oxygen free speaker cable? if the post system was lacking then why doesnt your battery fail on a regular basis? (devils advocate) clean post connections and cover in vaseline - no worries

Strangely enough........ milemarkers and Isuzu for me :lol: I can bump start my truck with a 9v battery B)

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Andy,

Earth cables should be as short as possible ;) ……………… and as moglite is a fully welded structure then the bulkhead would be the preferred option. Weld a bolt into the bulkhead use a braided earthy strap.

There was a bling RR sport parked outside your house yesterday ............. your new company motor ? :rolleyes:

Ian

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if the post system was lacking then why doesnt your battery fail on a regular basis? (devils advocate)

Conversely if it was an infaliable system why would you ever clean up the earthing strap connections to cure poor starting for example?

I just think connections that get regular dunkings in mud/water etc and then get pressure washed, like those on a chassis most likely would, do tend to suffer. Regular maintainance (hmmm vasaline) would avoid this problem of course, just like greasing yer uj's etc :rolleyes:

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I voted for none of the above.

If I was doing it, then I would connect the fat earths to the components that need them, i.e. those that draw massive currents; for example start motor, winches; in other words I would not go via that chassis.

The remaining small earths, for example gauges, indicators, lamps I would use the chassis.

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Celloseel QH JC11 DTD 900/4549 Jointing Compound, sold by PRC-Desoto, used on all MIL applications for sealing earth and bonding connections, problem solved :) Don't see Sea Kings, Chinooks and Nimrods failing to start in the morning as they got to clean the battery terminals before "turning the key" ;)

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Conversely if it was an infaliable system why would you ever clean up the earthing strap connections to cure poor starting for example?

ahh wasnt suggesting infallability - the concept of infallable and an electric winch being used in the same sentance would be like using "american military intelligence" complete gibberish......... but it would give it as good a chance of survival as any, anything will fail if its not maintained - I site my personal finances as a prime example :ph34r:

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The problem with any connection is that the smallest voltage difference between two bits of metal will encourage corrosion when wet, this is what happens when bits of telephone exchange get damper than they're supposed to be:

Wet_Vs_Dry_IDC_Tags.jpg

Any wonder battery terminals corrode so readily :blink:

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The problem with any connection is that the smallest voltage difference between two bits of metal will encourage corrosion when wet, this is what happens when bits of telephone exchange get damper than they're supposed to be:

Wet_Vs_Dry_IDC_Tags.jpg

Any wonder battery terminals corrode so readily :blink:

While the chassis is plenty up to it in terms of current handling, it's more about the number of connections between A and B.

A good example of this is my 8274. It draws 385 amps when stalled from the winch battery. The vehicle battery is connected to it through a split charge which involves an additional 5 properly made connections (including the relay contacts). The current pulled from the second battery is only 160A. Thus each connection is loosing (385-160)/5 = 45A

It is not quite as simple as that as there are other factors involved - but it is sufficient to say that each connection is reducing the max current available by a significant amount.

Reducing the connection count to the starter by two - as I'm suggesting will mean that you will be able to crank for longer from a flatter battery (particularly important on a V8 Auto!).

This also goes for the earth connection to the winch and anything else which benefits from higher currents.

De-oxygenated copper still corrodes. In practice the corrosion of the cable itself is limited. you tend to get more inside the terminals where it meets the cable. This is why it is important to crimp them properly (not just squash the terminal a bit in a vice :) ). Incidentally, soldering is not good for high currents, but crimping then soldering protects the connection from the atmosphere and gives you about as good a connection as you'll get.

In a previous life, I had to deal with low voltage (24v), 1200A and above connections where this kind of detail can make the difference between working and catching fire!

Si

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Chassis erfs and other short cuts are for pufta electrics - turbo boost gauges and panel lights. Don't matter if they fail. A few dunkings in ph 4 bogs will see a fine specimen of electrolytic corrosion on yer connections. The only way to do it if yr serioos is to run yer 35mm copper from bat earth to master cut out relay (450A rating) then to chassis bolt A, then from chassis bolt A to winch. The starter kin also go go from chassi bolt A. I've seen too many elec winches go us in flames (one one occasion while carrying on winching Rangie) not to put in cut out.

Put yr dead cut out switch in earth connection means when you later add all those fings wot you forgot about, and wire them direct to +ve bat, you'll still have master cutoff control.

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