Earthing Point Question.

Submitted: Sunday, Mar 28, 2004 at 22:34
ThreadID: 11640 Views:1826 Replies:7 FollowUps:1
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Hi All,
I am installing a extra 12 volt. cigar point at the rear seats of my L/C 80 where my Waeco 50 liters located during a long trip. I am wondering if there is any reason I should run the earth ( ground) cable from the battery or just from nearest earthing point. From the theory I learnt in school It seems fine to earth to the nearest chassis. Is there anyone can help me finding the best answer? your help is much appreciated.
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Reply By: joc45 - Sunday, Mar 28, 2004 at 23:06

Sunday, Mar 28, 2004 at 23:06
Correct. Just find a good point on the body to bolt your earth lug to, such as sharing another point used by the vehicle electrics. Just make sure that there is no paint to degrade your earth, and don't used a self-tapper, try to find a good threaded point to bolt onto. And use a proper copper lug to match both the cable diameter and the bolt diameter, don't just wrap the wire around the bolt and tighten it. Make sure you have a decent guage wire back to the +ve of the battery, and a fuse or circuit breaker back near the battery.
AnswerID: 52345

Reply By: Rosco - Bris. - Monday, Mar 29, 2004 at 07:45

Monday, Mar 29, 2004 at 07:45
As Gerry says ... but if the Waeco plug is the type with the red plastic ring around it, whip it off and get one of the Hella? female clip in sockets that matches. Very neat with a clip together connection that won't fall out like an ordinary cigar lighter type. You can get flush mounting ones that you fix to the boby with a couple of 3mm metal threads or rivets. The earth is built in so all you need do is scrape off a tiny bit of paint around the relevant hole. Good for up to about 8 amps.
AnswerID: 52358

Reply By: Member - John - Monday, Mar 29, 2004 at 07:48

Monday, Mar 29, 2004 at 07:48
Chenj3, I would not use a cigarette lighter, i would use a hella/narva plug, more secure and less voltage drop. I would also run the earth back to the battery, again less chance of voltage drop. Just my 2 cents worth. John
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AnswerID: 52359

Reply By: The Banjo - Monday, Mar 29, 2004 at 08:41

Monday, Mar 29, 2004 at 08:41
Some guru told me at some stage that running both earth and suppy direct from the battery gives you the best performance potential (literally)....seems that the battery being the source, we should go direct to that source with + and - , when we can. To earth via the chassis is a convenient the case of most carminor circuits, it doesn't matter.....anyway, its not possible to have them all running straight off the battery poles ! For me, radios, fridges and aux batteries (trailer ones too) all go direct to the main (both + and - side)......with a fuse in line foreveryseperate circuit, at the main battery end.
AnswerID: 52361

Reply By: chenj3 - Monday, Mar 29, 2004 at 13:33

Monday, Mar 29, 2004 at 13:33
Hi All,
Thank you all your comments.
It seems that there is no majpr technical problem earthing to the chassis for electrical accessories. In terms of electrical resistance back to the V- on the battery, I reckon it may be a more efficient way to run it through chassis as multiple paths, i.e. thousands of welded points on the chassis. rather than a single 3+ mteters long, 4mm/20A cable back to V-.

By the way, The female cigar socket I bough from AutoBarn yesterday was labelled for $16.99 but I paid $7.99 from promotion. What a profit! I would NOT be surprised if AutoBarn just paid $1.00 from their wholesalers.

Thank you again for your help.

AnswerID: 52399

Follow Up By: Member -Bob & Lex (Sydney) - Monday, Mar 29, 2004 at 17:00

Monday, Mar 29, 2004 at 17:00
4mm cable to small go at least 6mm & back to battery, but your choice. do a topic search as this has been done a 100 times.
FollowupID: 314215

Reply By: Member - John - Monday, Mar 29, 2004 at 15:51

Monday, Mar 29, 2004 at 15:51
chenj3, I can not fathom why you asked the question in the first place? 50% of the replies stated it was not a good idea to earth thru the chassis, but you are going to do it any way. 75% said don't use a cigarette lighter pug, but that's what you are going to do. Fair enough, your call, but why bother asking, wasting our time and yours?
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AnswerID: 52425

Reply By: Member - Steve - Monday, Mar 29, 2004 at 20:18

Monday, Mar 29, 2004 at 20:18
You may have many paths back to the earth but that makes many failure points. The voltage drop is large enough to stop your waeco 5 to 6 hours before isolated looms because of that. If you have a short or dry connection some where it will be harder to trouble shoot. The Cig ligther is OK for lights but use deciated connectors for the Fridge. 6mm is the smallest you should run to the back and if you are going to all that trouble run 2-3 looms. 1 8mm if you can afford it. You may want to run an inverter one day. The fridge will run well with 6mm
AnswerID: 52473

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