battery cable

[tricks]

I'm after moving my battery into the pick up of my 90 but i dont have a clue what rating the new cable should be after copius google searches

hopefully one of you helpfull chaps knows

Thanks

James

[LandyManLuke]

35mm^2 csa is a good place to start, 50mm^2 csa if you're overly concerned about voltage drop under load, or do lots of winching etc.

[ldtopham]

If it's any use I recently measured the current draw when cranking my 300tdi (summer weather) just short of 400amps.

[zardos]

It might help if you give some more details on the engine as diesel starter motors tend to draw more starting current than petrol.

Also do you have any high load devices (winch, inverter, lots of lights) wired via this cable you want to replace.

Can you not measure the diameter of the old wire? and then convert with simple maths to sq mm.

Generally I believe that 40 sq mm is commonly used for battery cables (good for around 300 Amps continuous)

Note that a starter motor can draw up to 600 Amps peak but a more common use case is around 300 Amps (but again only for a short period of time).

Other info that might help decide on the size is a lot of the FIA master switches are rated 100 Amp continuous 500 Amp peak this would suggest 16 sq mm (110 Amp continuous)

But I would not go anything less than 25 sq mm

[zardos]

35mm^2 csa is a good place to start, 50mm^2 csa if you're overly concerned about voltage drop under load, or do lots of winching etc.

For winching it is generally the rule to use separate + and - wires with cheaper winches coming with 35 sq mm wires but if you have a serious winch and use it hard then there is no wire big enough for the max load (you need a 150 sq mm solid bus bar).

[ldtopham]

For winching it is generally the rule to use separate + and - wires with cheaper winches coming with 35 sq mm wires but if you have a serious winch and use it hard then there is no wire big enough for the max load (you need a 150 sq mm solid bus bar).

I have another vehicle which has high cranking amps (6ltr V8 high compression American motor) and as the price difference wasn't huge for the amount of cable I needed just went belt and braces approach. I fitted 70mm2 flexible cable and never have had any supply or voltage drop problems.

For a pure battery isolator (not for isolating a running engine) I can recommend the Durite Part No. 0-605-20 designed to cope with 500 amps for 5 seconds. It also has a removable proper cut key. again I've run one of these without problem on the same vehicle with 70mm2 cable.

[tricks]

It might help if you give some more details on the engine as diesel starter motors tend to draw more starting current than petrol.

Also do you have any high load devices (winch, inverter, lots of lights) wired via this cable you want to replace.

Can you not measure the diameter of the old wire? and then convert with simple maths to sq mm.

Generally I believe that 40 sq mm is commonly used for battery cables (good for around 300 Amps continuous)

Note that a starter motor can draw up to 600 Amps peak but a more common use case is around 300 Amps (but again only for a short period of time).

Other info that might help decide on the size is a lot of the FIA master switches are rated 100 Amp continuous 500 Amp peak this would suggest 16 sq mm (110 Amp continuous)

But I would not go anything less than 25 sq mm

hi sorry for lack of detail ... its a 90 with a 200 tdi disco conversion that im currently rebuiling after a lil falling over incident

it will be having a winch on it and a fair amount of lighting once its done.

Its a bit of a mare to just measure the old wire beacuse its parked at a workshop about an hour away from where i live i usually only go up at the weekend

thanks for your help much appricated

James

[zardos]

I have another vehicle which has high cranking amps (6ltr V8 high compression American motor) and as the price difference wasn't huge for the amount of cable I needed just went belt and braces approach. I fitted 70mm2 flexible cable and never have had any supply or voltage drop problems.

For a pure battery isolator (not for isolating a running engine) I can recommend the Durite Part No. 0-605-20 designed to cope with 500 amps for 5 seconds. It also has a removable proper cut key. again I've run one of these without problem on the same vehicle with 70mm2 cable.

70mm2 is not belt and braces for a twin motor winch (each motors max load is 500Amp for a 9500 lbs line pull), it would be just OK for a single motor winch.

Things to remember though:-

That's max load, how often do you hit that and for how long, probably not that often and not for long.

With twin motors, your max load doubles but on the same load it will draw about the same current.

As for isolators, I have melted the Durite one as it's only 250A continuous and it's easy to winch for more than 5 seconds.

Having said all this about max load and continuous load I also have run 70mm2 extra flex cable on twin motors without any problems other than getting vaguely warm (not enough to melt).