Which Cable for Battery Leads

[John P]

Hi,

Having now sorted out the floor mounted starter on my Ulsteroid and also added a battery isolator switch I need to get some battery leads made up.

I'm planning to run an earth lead from the battery's negative post to the isolator switch (which is mounted on the passenger seat front support) and then from this switch to both a bolt through the floor adjacent to the battery and also, via a second lead, to one of the starter motor mounting bolts.

On the positive side there will just be a lead from the battery to the starter button and then from the button to the starter motor.

On e-bay a supplier can make up any length of lead using a variety of cable sizes from 16 mm² up to 95 mm² but which should I choose?   I'm assuming that a larger size will help reduce voltage drop but larger is also more expensive and presumably more difficult to run neatly.

Any advice,

John.

["Slack Alice" Simon]

Measure the hole in the connector and work out the area you can use.

With 6 volts the thicker , the better, within reason.   If it won't go into the terminal connector, it isn't reasonable.

[Howard Wright]

Hi John

Just curious!  Why isolate the earth side?

I’ve always isolated the live side but I know there are arguments for both.

What do others think?

I think 160amp cable is often suggested for battery connections.

I believe the battery to isolator switch cable should be as short as possible.

Cheers

Howard

[Henry Harris]

This company can supply all the bits you need.....

https://www.autoelectricsupplies.co.uk

[Zetomagneto]

Hi Howard
On the old Lucas isolators there is a small terminal that runs to the cb connection on the coil to
earth it when the switch is turned off, I have always put the switch on the earth side but my memory does not go back far enough to know why!My Morgan came with an isolator on the earth side.

[Chris KC]

Seven Workshop stocks an eminently suitable cable.

[Stuart Giles]

Hi John

Just curious!  Why isolate the earth side?

I’ve always isolated the live side but I know there are arguments for both.

I've always understood that the thinking behind having the earth connection going through the isolator rather than the live is that a short circuit from one of the isolator terminals to earth won't cause an impressive firework display or electrical fire.

Re. battery cable I always use 25 sq mm welding cable like this:

https://www.ebay.co.uk/itm/Copper-Weldin...f2xFKWHN2A

25 sq mm cable has an outside diameter of about 12mm. If you get the cable from your local welding supplier, they will usually crimp the terminal lugs on for you while you wait. If you have a hydraulic press in your garage, making a press die to crimp the lugs yourself is a simple job.

[Howard Wright]

Hi All

Yes it probably does seem more sensible to isolate the earth.  However I’ve used un-insulated (braided) cable for the earth strap in the past.  I guess if you are going to isolate the earth you need to use insulated cable.

John, It quite easy to make up your own cables rather than get ones made up.  AES and others sell all the required parts.

Cheers

Howard

[Jeff Taylor]

I’ve posted the following before on the forum regarding battery / starter cable specification and suppliers of the correct cable and terminals. As this is a copy of an old post, the prices may have increased.

Re having the correct size of battery / starter cables for 6v – the links below take you to suppliers of the correct specification battery / starter cable to buy for a 6v system.

Battery / Starter Cable – 315/0.40, 40mm², 13mm OD, 300A

AES stock it in cotton braid black or red – their Ref. No. 020203 @ £8.97p per metre:

https://www.autoelectricsupplies.co.uk/p…#flash-msg

The Green Spark Plug Company stock it in PVC black or red – their Ref. No. 0-982-10 @ £11.81p per metre:

http://www.gsparkplug.com/1x-meter-durit…82-10.html

Battery Clamps, Terminals & Covers:
http://www.gsparkplug.com/battery/batter…covers?p=1

https://www.autoelectricsupplies.co.uk/product_list/32

[Howard Wright]

I’ve posted the following before on the forum regarding battery / starter cable specification and suppliers of the correct cable and terminals. As this is a copy of an old post, the prices may have increased.

Re having the correct size of battery / starter cables for 6v – the links below take you to suppliers of the correct specification battery / starter cable to buy for a 6v system.

Battery / Starter Cable – 315/0.40, 40mm², 13mm OD, 300A

AES stock it in cotton braid black or red – their Ref. No. 020203 @ £8.97p per metre:

https://www.autoelectricsupplies.co.uk/p…#flash-msg

The Green Spark Plug Company stock it in PVC black or red – their Ref. No. 0-982-10 @ £11.81p per metre:

http://www.gsparkplug.com/1x-meter-durit…82-10.html

Battery Clamps, Terminals & Covers:
http://www.gsparkplug.com/battery/batter…covers?p=1

https://www.autoelectricsupplies.co.uk/product_list/32

Hi Jeff

I was a bit surprised by the battery cable size.  The Seven Workshop stocks armoured battery cable for 23 to 32 cars that is 180 amp.  I’ve used this on my RK with no problems.

I haven’t been able to find armoured cable any larger than 180amp.

Are you saying this is not suitable? Or is it OK for early cars?

Cheers

Howard