What size battery cable?

Redsteve · December 13, 2016

Hello Guys.

I hope you are all enjoying the festive season.

I just have a quick query about the positive Battery cable on my 2000 LS400.

I need to replace a small part of the cable due to damage but I not sure what the cable needs to be rated at. I have seen cable rated from 100A up to 450A so I thought just go for the biggest.

However, when I checked my Battery it is rated at 60Ah and 540CCA. Does this mean I need a cable rated at 540A?

Thanks.

Steve.

Britprius · December 13, 2016

Although the Battery is rated at 540 cranking amps you do not need a cable with that high a rating. Generally the thicker the better as this reduces the resistance, and therefore the voltage drop along the cable when starting the engine. Use a cable at leased as thick as the OEM. This translates into a faster cranking speed, and engine start. Joints in the cable are usually troublesome, and should be avoided if possible. End connections should be soldered on rather than crimped if possible.

It is a good idea to check all the Battery cable connections including from the chassis to the engine for cleanliness, and tightness. Single loop steel spring washers are not a good idea to use.

steve2006 · December 13, 2016

I would suggest a minimum 25mm CSA copper cable.

sorcerer · December 13, 2016

It can sometimes be difficult equating cross-sectional area sizes to physical sizes but this website helpfully lists both, so you should be able to measure the diameter of your existing cable to match it up.

Redsteve · December 14, 2016

Many thanks for your replies.

I will have a measure up and check out the website suggested by sorcerer.

I will also make sure that I get the ends soldered as it makes perfect sense to have as secure a connection as possible.

Hopefully I will get the cable replaced before Christmas as it is becoming a lottery on whether or not the old Lex will start without wiggling the Battery cable and then waiting for 6 minutes before I can start the car (most embarrassing on a petrol station forecourt).

Steve.