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Battery earth wiring
AdamR - 21/12/08 at 12:24 PM

What's the consensus on the following options:

1) Battery earth wired to chassis; chassis to engine earth strap to earth engine
2) Battery earth wired to engine; chassis to engine earth strap to earth chassis

The first option is easiest/neatest to do, but I've got a hazy memory about having read something suggesting the engine should be earthed directly to the battery....

mookaloid - 21/12/08 at 12:30 PM

I'd go for option 1 myself - as long as the connections are good, there should be no advantage to using option 2.

With 1 if the engine earth strap breaks, the car won't start. With option 2 all the electrics could go if the earth strap breaks

Cheers

Mark

David Jenkins - 21/12/08 at 12:59 PM

I have a threaded post welded into the chassis, where the battery -ve and engine earthing strap are bolted down. So Option 1 was my choice!

MikeRJ - 21/12/08 at 01:05 PM

quote:
Originally posted by mookaloid
I'd go for option 1 myself - as long as the connections are good, there should be no advantage to using option 2.

With 1 if the engine earth strap breaks, the car won't start.


It won't start but it may well melt control cables etc. However, virtually all production cars I have ever seen use this method.

The advantage to option 2 is that you minimise any voltage drops to the starter motor.

rusty nuts - 21/12/08 at 01:19 PM

I agree with Mike , option 2 although both work

mookaloid - 21/12/08 at 02:17 PM

quote:
Originally posted by MikeRJ
quote:
Originally posted by mookaloid
I'd go for option 1 myself - as long as the connections are good, there should be no advantage to using option 2.

With 1 if the engine earth strap breaks, the car won't start.


It won't start but it may well melt control cables etc. However, virtually all production cars I have ever seen use this method.

The advantage to option 2 is that you minimise any voltage drops to the starter motor.


Also true

Maybe the real answer is - have several earth straps/chassis connections so that if one breaks you are still ok

Cheers

Mark

AdamR - 21/12/08 at 02:51 PM

quote:
Originally posted by MikeRJ
The advantage to option 2 is that you minimise any voltage drops to the starter motor.


Why would there be a bigger voltage drop? Surely the chassis is just as good a conductor as a battery cable?

Macbeast - 21/12/08 at 04:04 PM

In Option 2 there is only one joint in the battery to starter feed - in Option 1 there are two.

coozer - 21/12/08 at 05:41 PM

I used the Sierra battery cables unmolested.
There is a short strap earth that comes off the battery and is attached to the chassis above the battery, (footwell for me) The standard earth is bolted to this and is the same length as the starter live cable so goes down to the starter and is bolted to the engine block.

speedyxjs - 21/12/08 at 06:07 PM

quote:
Originally posted by MikeRJ
quote:
Originally posted by mookaloid
I'd go for option 1 myself - as long as the connections are good, there should be no advantage to using option 2.

With 1 if the engine earth strap breaks, the car won't start.


It won't start but it may well melt control cables etc. However, virtually all production cars I have ever seen use this method.


I have had experience of this. I can tell you, it is NOT fun trying to drive a car with a basically welded throttle cable