An earthing question
Submitted: Monday, Mar 26, 2007 at 07:51
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Willem
In post 43634( OT. A palandrome by itself...lol) Member Jiarna NT states that he has earthed the Aux Battery to the engine, as he had had problems with cranking batteries.
I have recently installed a HD cable as earth wire to my Auxilliary battery and earthed to the body of the truck.
Which is best?
Cheers
Reply By: Gronk - Monday, Mar 26, 2007 at 08:43
Monday, Mar 26, 2007 at 08:43
If the aux batt is right beside the main batt, earth it straight to the main batt neg post !! But, whichever is the shortest or easiest route ??
I would prefer it to the engine block before using the body !! Same with using say the chassis for earthing the neg of a trailer plug...always
check that the chassis is earthed and what size earth lead is used ??
AnswerID:
229748
Reply By: Wayne (NSW) - Monday, Mar 26, 2007 at 10:16
Monday, Mar 26, 2007 at 10:16
Willem,
I have got a earth cable, from the aux battery to the body and to the 4.2TD.
To be sure to be sure.
When I wire any accessory, as I am in the middle of doing now I always run the positive from the battery through a fuse and the negative back to the battery. I don't use the body as a return to the battery.
Probably a over kill but I don't have bad earth problems, just bad hair days.
Wayne
AnswerID:
229768
Follow Up By: Peter 2 - Monday, Mar 26, 2007 at 18:49
Monday, Mar 26, 2007 at 18:49
Wayne
I used to fit HF radios and we NEVER connected the earth or negative lead to the battery but rather the engine or body end of that lead.
The reason is that if for some reason the negative lead connection between the engine and/or body became high resistance or became totally disconnected then the starting current would then take the path of least resistance which is usually the HF or other accessory with the fattest cabling.
The end result is not pretty, cranking astarter when the HF is making the negative connection destroys the radio, it usually happens very quickly and makes a toatl mess of the insidesof the HF and sometimes the autotune antenna as
well.
Car frigs and air compressors don't last long either ;-))
By all means run the negative for your accessory back to the battery but connect it to the body or engine end of the negative cable not the battery end.
If you must run the accessory negative to the battery then fuse it as
well but this defeats the original purpose of making a good connection as the fuse can add resistance and future connection problems.
FollowupID:
490614
Reply By: Dave198 - Monday, Mar 26, 2007 at 11:03
Monday, Mar 26, 2007 at 11:03
Funny you should mention that Willem.
I have just finished wiring up an Anderson plug for the CT, and came across an earth lead in my box of various electrical bits.
My aux battery is earthed to the engine at the moment, and I thought that with this earth lead I just found, I might just put that between the engine and the chassis.
Overkill ? I don't know.
Dave
AnswerID:
229780
Follow Up By: Nick R - Monday, Mar 26, 2007 at 12:15
Monday, Mar 26, 2007 at 12:15
My auto lekky suggests this is a good idea
NickR
FollowupID:
490540
Reply By: Member - Phil G (SA) - Monday, Mar 26, 2007 at 12:09
Monday, Mar 26, 2007 at 12:09
The aux battery needs to be earthed to the engine (or more precisely, the alternator body) to maximise battery recharging. This earth lead may be required to carry up to 40-50amps, if you're recharging 2 or more batteries so its very important.
It also needs to be earthed to the body so your accessories work - this earth may only carry up to 10amps for fridge and lights.
If you earth only to the body, you are more likely to undercharge your battery.
Manufacturers run 2 earth leads - fat one to the motor and thinner one to the body. Simplest solution is the earth 2nd battery to the neg terminal of the cranking battery, but you can also run 2 separate earths to engine and body.
AnswerID:
229796
Reply By: Willem - Monday, Mar 26, 2007 at 19:50
Monday, Mar 26, 2007 at 19:50
Thanks everyone for all the indepth replies.
I shall fit a fat cable from the Aux negative terminal to the engine. It is already earthed to the body but I suspect it has been undercharging as Aux battery only show 12.45volts late today.
I had an inferior cable to the engine but decided to improve the situation, earthed the Aux to the body and then forgot about earthing it back to the engine. Old age...lol
Cheers
AnswerID:
229876