Battery cable rating

[davehall]

I've got some starting issues which I think might be due to battery positive and/or negative lead failing, so am going to renew the lot but not sure what cable amperage rating I need. It's a 1.8 Zetec so any views?

Car starts fine when I jump it from the tiptop. The battery is fairly new so doubt it's that.

TIA

Dave

[steve m]

Dave,

If you think your cables are ok, and it still struggles to start ? try this first before wasting money on cables

Firstly with a fully charged battery, as in been on charge all night does the car start ok, if yes, its 99% your battery is shagged
If no, take one jump lead, from the neg side of the battery, and the other to a good sized bolt on the engine /gearbox, does it start ok, if yes, you have a bad earth somewhere, if no, take it off, and replace it to the plus side of the battery, and the other end to the starter relay/starter motor

Does it start ok ? if yes, the plus side has a problem, and replace said wiring,
If no, call an electrician or change the brushes in the starter motor!!

Seriously, it can only be one of the four scenario's above, battery, neg side, positive side, starter brushes

As a side to the above, my crossflow had real problems starting, and it was so hit and miss, sometimes it was fine, others it would struggle, I added or changed cables, etc, and finally after losing the starter motor on the M4 a few years ago, installed a high torque starter motor, and NEVER had an issue since

steve

[davehall]

Steve

Last time I tried starting after an overnight charge it wouldn’t start. I hadn’t thought of using a jump lead like you’ve suggested so that’s the next thing to do.

Ta

Dave

[jeffw]

Put a voltmeter over the battery terminals and see what the voltage is when it is charged.

[Davemg]

Straight answer, 25mm trirated. Remember you will be pulling about 180 amps on cranking, and the last thing you want is any volt drop. A fraction of an ohm will result in significant loss of useable volts.

Secondly, battery should read 14.5v when being charged by the alternator, and about 12.5v with engine off, battery fully charged.

Thirdly, if you renew cables, remember to ensure there is a fusible link somewhere. I put a 250A fuse in the positive line right out of the battery for safety’s sake. OEMs sometimes have a Hyperlon (wire) fuse in the Harness that is not obvious.

If you crimp connectors to 25mm, you’ll need a hydraulic crimper, but the two-screw type terminals are almost as good IMHO.

[David T]

I used 175A for the main cables and then 125A I think for the alternator.

I used the Laser anvil type crimp and it worked well.

[davehall]

Thanks for the replies guys. However, i’ve eliminated the cables and all connections so was convinced it’s the starter and after removing it i’m even more sure!

So a new shiny Powerlite has arrived. Fitted it today but the opening in the “cone” covering the bendix is fouling the ring gear. Removed it and compared to the old starter and it’s obvious that the opening is at a slightly different angle, hence the fouling. This is on a silvertop Zetec.

Does anybody know if it’s adjustable and if so, how, or do I need to return it?

Dave