Battery negative / earth lead position

[michael4]

On a late car which has been converted to negative earth where is the best location for the lead to be bolted to the car?

Is the side of the battery box OK?

Ours currently has a isolator switch dangling down under the glove box with the lead coming in through the bulkhead. It is then bolted to the bottom of the dashboard.

OK so it works but to me it is all wrong. I'm not too bothered about the security aspect so will fit a simple isolator at the negative terminal.

[philthehill]

There is nothing wrong with the earth lead being bolted to the side of the battery box. That is where it was mounted originally.

[les]

This is my set up ———as Phil has mentioned

IMG_2054.jpeg (493.6 KiB) Viewed 4597 times

[philthehill]

With a isolator battery terminal connector as well.

[michael4]

Many thanks, that is exactly what I wanted to do.

It is looking very tidy in there!

[Sleeper]

I took mine down to where the engine earth lead bolts to the body , there are a lot of amps there when cranking...

John ;-)

[geoberni]

I took mine down to where the engine earth lead bolts to the body , there are a lot of amps there when cranking...

John ;-)

Your car, you can do what you wish, but that's a complete waste of time and effort.
The amperage cranking the engine over for a Minor is only around 110-120 Amps.
The structural bodywork of the car is far more suitable for taking that than a length of cable, where you have to consider the current, the duration of it and the losses along the cable.

Battery return/earth connection should be to vehicle structure, as near the battery as practical.

As we're posting battery photos, here's Basil's, before and after his faux 1950's Lucas makeover last year .

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20230501_094638.jpg (1.4 MiB) Viewed 4507 times

[Sleeper]

I think we'll have to disagree on that...

" The amperage cranking the engine over for a Minor is only around 110-120 Amps. "

As Lance Corporal Jones would say , " They wouldn't like that up 'em... "

All I can say is that my cranking improved after I re-routed the Earth straight from the -ve to the starter motor bolt via the body.

cable.jpg (200.9 KiB) Viewed 4454 times

John ;-)

[philthehill]

If your cranking improved after fitting the additional lead then you must have had a continuity problem and the additional lead was a get round fix.
My battery is in the boot and relies on continuity through the body and I never have had a problem. I have just made sure that the earth/return cable is well grounded with clean rust/paint free connections. The additional length of cable has not effected the continuity or power.
I would also suggest that you need a proper nut and spring washer not a wing nut on that connection joint.
That is an interesting engine steady bracket by the damper - has it got a slot instead of a plain hole?

[Sleeper]

" That is an interesting engine steady bracket by the damper - has it got a slot instead of a plain hole? "

Yes, just a length of screwed s/s, slotted brackets at both ends, makes for easier removal.

John ;-)

P.S. There is a spring washer and plain washer on the cable fixing.

[geoberni]

I think we'll have to disagree on that...

" The amperage cranking the engine over for a Minor is only around 110-120 Amps. "

As Lance Corporal Jones would say , " They wouldn't like that up 'em... "

All I can say is that my cranking improved after I re-routed the Earth straight from the -ve to the starter motor bolt via the body.

John ;-)

Your original comment and your photo don't match the standard set-up.
The original circuit is Battery Earth to Car Body, Starter Earth via it's casing, connected to gearbox, which is strapped to Body.
Unless you've done it, a previous owner has added that Bolt & Wing Nut, probably because they didn't understand how vehicle electrics work, perhaps not even knowing where the gearbox strap was....

The 110-120 Amps of the Minor is nothing compared to starting a modern car, particularly Diesels, which can be over 400Amps.

[Sleeper]

" Your original comment and your photo don't match the standard set-up."

Well spotted, it is nowhere near standard , with a heavy gauge cable from Battery ( -ve ) earth to starter mounting via body connection...

John ;-)

( 37 years Electrical Engineering )

[geoberni]

( 37 years Electrical Engineering )

Snap - 37 yrs aircraft electrical engineering, like cars but more complicated.